History

13.8 billion years ago (Ga). Space, time, matter and energy begin from a hot dense state and expand; within minutes the light elements exist, after 380,000 years the universe cools enough to become transparent, and the light released then is still arriving as the cosmic microwave background. First stars by around 13.6 Ga, and they matter because everything heavier than helium — the carbon in you, the iron in your blood, the oxygen you breathe — is manufactured inside stars and scattered when they explode. There is no other source.

4.6 Ga. A cloud of gas and dust — enriched by earlier generations of exploded stars — collapses into a star with a disc of debris around it, and the debris accretes into planets. Around 4.5 Ga a Mars-sized body strikes the young Earth and the ejected material becomes the Moon, which is why the Moon's composition matches Earth's mantle. That impact also gives Earth its axial tilt, so it gives us seasons, and the Moon's tidal drag has been slowing the day down ever since.

About 3.8 to 3.5 Ga, within a few hundred million years of the Earth's surface becoming habitable at all — which is fast, and is the main reason for thinking life may not be rare. It is single-celled, anaerobic and confined to water, and it stays essentially at that level of complexity for well over a billion years. Everything alive today descends from a single common ancestor, which is why all life uses the same genetic code and the same handedness of molecules.

2.4 Ga. Cyanobacteria invent photosynthesis and start dumping oxygen — to everything then alive a corrosive poison — into an atmosphere that had none, causing what may be the largest mass extinction in Earth's history and possibly a global glaciation. It is the first time life reshapes the whole planet rather than merely living on it. It is also the precondition for everything on the rest of this face, because oxygen respiration yields roughly ten times the energy of the alternatives, and large active animals cannot be powered any other way.

About 1.8 Ga a cell swallows a bacterium and does not digest it; the passenger becomes the mitochondrion and the result is the eukaryotic cell, with a nucleus and an internal power supply — an event that appears to have happened exactly once. Sexual reproduction follows around 1.2 Ga, which speeds evolution enormously by shuffling variation instead of waiting for mutation. Multicellular life around 0.8 Ga. Three bottlenecks, each of which took hundreds of millions of years, and none of which had to happen.

541 million years ago (Ma). Within perhaps twenty million years — an eyeblink at this scale — almost every major animal body plan alive today appears in the fossil record: eyes, shells, limbs, guts with two openings, predators and therefore prey. The likely triggers are rising oxygen and the arms race that begins the moment one animal starts eating another. Plants reach land around 470 Ma and vertebrates around 375 Ma, and the coal that powers era 08 of the spine is the buried forests of the period that follows.

252 Ma. The end-Permian event kills around 90 per cent of marine species and 70 per cent of land vertebrates — the closest complex life has come to ending — most probably through vast volcanic eruptions in Siberia releasing carbon dioxide, warming the planet, acidifying the oceans and stripping them of oxygen. Recovery takes some ten million years, and what fills the emptied world is the dinosaurs. The mechanism is worth holding precisely because it is carbon dioxide released fast into an atmosphere.

66 Ma. A ten-kilometre object strikes Yucatán at Chicxulub, and the impact winter kills every dinosaur that is not a bird along with three quarters of all species. Mammals had existed alongside the dinosaurs for 150 million years as small nocturnal things, and only in the emptied world do they grow large and diversify — primates among them. Nothing about that was earned. If the asteroid misses, the reasonable expectation is that dinosaurs still hold the large-animal niches and no one is reading this.

About 7 Ma the lineage leading to us splits from the one leading to chimpanzees. Bipedalism comes first and early — Australopithecus is walking upright by 4 Ma with a brain no bigger than a chimp's, so standing up was not a consequence of intelligence but a precondition for it, because it freed the hands. Stone tools by 3.3 Ma, Homo erectus out of Africa by 1.9 Ma, and control of fire somewhere between 1.5 Ma and 400 ka — which externalises digestion, since cooking makes calories available that a raw diet cannot, and pays for an expensive brain.

About 300 thousand years ago (ka), anatomically modern humans in Africa; by 100–70 ka the behavioural package is unmistakable — symbolic ornament, long-distance trade, projectile weapons — and populations leave Africa and reach Australia by 65 ka and the Americas by around 16 ka. They interbreed with Neanderthals and Denisovans, whose DNA most living people still carry a small percentage of, and then are the only human species left by around 40 ka. The cave art of Sulawesi, Chauvet and Lascaux belongs here: people with our minds exactly, thirty thousand years before anyone wrote anything down.

About 12 ka the last ice age ends and the Holocene begins — a climate stable and warm enough to make farming possible — and within a few thousand years agriculture is invented independently at least seven times: the Fertile Crescent, China, New Guinea, Mesoamerica, the Andes, west Africa and eastern North America, by people with no contact. That independence is the argument that it was a response to shared conditions rather than a single lucky idea. It is not obviously a good deal for the individual: early farmers are shorter, sicker and worked harder than the foragers they replace. What farming buys is not a better life but more people, and denser people, on the same land.

5.5 ka, and the last few centuries before era 01's first hour. Farming villages become towns with walls, granaries, temples and ranks; the plough, irrigation, the potter's wheel, woven textiles and copper metallurgy all arrive; Göbekli Tepe in Anatolia shows monumental building by around 11.6 ka, before farming, which reverses the assumed order and suggests it may have been the need to feed the builders that pushed people to farm. Then southern Mesopotamia irrigates a floodplain, produces more grain than it eats, and the spine begins.

Southern Mesopotamian villages irrigate, grow more grain than they eat, and concentrate — Uruk reaches perhaps 40,000 people, an order of magnitude beyond anything before. The surplus supports a temple bureaucracy that stores and redistributes it, the first institution that is neither family nor village, and it arrives with a whole toolkit: wheel, plough, sail and bronze. Bronze is the one that sets the terms, because copper is common but tin is rare and far away, so the era's best weapons can only exist where long-distance trade does — which makes them a rich man's monopoly for two thousand years.

Cuneiform in Sumer and hieroglyphs in Egypt within a couple of centuries of each other, and both begin as accountancy — tallies of grain, sheep and labour, not poetry. Writing is what makes slot 1's redistribution auditable and therefore scalable beyond what one man can remember; literature is a side effect that takes another thousand years to arrive. It is invented independently four times in history — here, in China around 1200 BC, and in Mesoamerica — and never a fifth.

Narmer joins Upper and Lower Egypt into a single state along a river that floods predictably and is walled by desert on both sides. Predictable flood plus no land neighbours equals the most stable state in human history — recognisably the same civilisation three thousand years later, which is a longer gap than the one between it and us. Mesopotamia, open on every side, spends those same three thousand years being conquered by somebody new every few centuries, and the contrast is the clearest case on the spine of geography setting political form.

Egypt's Old Kingdom builds Giza, and in the same centuries the Indus valley builds Mohenjo-daro and Harappa — grid-planned, drained, standardised in brick size across a thousand kilometres. The contrast is the lesson: Egypt spends its surplus on one enormous tomb and leaves us its kings' names, while the Indus spends it on plumbing for everybody and leaves us a script we still cannot read. Surplus is a choice about what to build, and what you build determines what you are remembered by.

Sargon conquers the Sumerian city-states and rules them from a single capital with a standing army and appointed governors, rather than taking tribute from local kings who stay put. This is the invention of empire as an administrative form — not "I beat you" but "I now run you" — and it is the template every later Mesopotamian ruler claims to be restoring. It lasts under two centuries and is remembered for two thousand years.

Around 2200 BC a severe multi-century drought hits from Egypt to the Indus at once: Akkad ends, Egypt's Old Kingdom falls into the First Intermediate Period, the hyper-documented bureaucracy of Ur III collapses within a century, and over the following centuries the Indus cities are abandoned with no conquest at all — the rivers shift and everyone leaves. These states are irrigation machines, and an irrigation machine is a bet on the climate. What rises from it is Babylon, whose Hammurabi publishes 282 laws on a public stele in the marketplace, above his own name: the content is unequal by design, but a written rule is a rule the king can be held to.

The spoked-wheel chariot and the composite bow re-arm everyone — Hittites in Anatolia, Hyksos ruling Egypt, chariot-borne Indo-Aryans entering north India, and Shang China appearing in the record complete with chariots and oracle-bone writing. It is expensive kit, so it entrenches aristocracy exactly as bronze did. On top of it sits an international system: Egypt, Hatti, Assyria, Babylon and Mycenae exchanging diplomats, gifts and royal brides in Akkadian, the Amarna letters addressing each other as "my brother", and Kadesh in 1274 BC producing the first surviving peace treaty. Interlocked, prosperous, and every link a dependency.

Within about fifty years every palace civilisation from Greece to the Levant fails — Mycenae, Hatti and Ugarit burned, Egypt surviving but shrunken. No single cause holds up: drought, earthquake, the Sea Peoples, internal revolt and the failure of the tin trade all appear, and the modern reading is systems collapse, where a tightly-coupled network transmits failure instead of absorbing it. Writing is lost in Greece for four hundred years. It is the sharpest break on the whole spine and it clears the board for everything after it.

The Zhou overthrow the Shang and justify it with a doctrine that outlives them by three millennia: heaven grants the right to rule conditionally, and misrule — read as flood, famine or defeat — revokes it. It is simultaneously the strongest possible claim to legitimacy and a standing licence for rebellion, since a successful rebel is by definition the one heaven now favours. China acquires its theory of political change here and keeps it through every dynasty until era 09's twelfth hour.

Iron ore is everywhere, so a technology that needed slot 1's long-distance tin is replaced by one a village smith can supply, and an army becomes a question of manpower rather than of aristocratic monopoly. In the same centuries the Phoenicians carry a 22-letter alphabet around the Mediterranean, learnable in days where cuneiform took years. Assyria is what a state does with both: iron infantry, siege engineering, road and relay systems, mass deportation of conquered peoples, and atrocity publicised as policy on its palace walls. It holds Mesopotamia, the Levant and Egypt together until a Babylonian and Median coalition erases Nineveh in 612 BC — destroyed by the peoples it had trained in its own methods.

Within roughly a century, and mostly without contact, the world's durable ethical systems get stated: the Buddha and the Upanishads in India, Confucius and Laozi in China, Zoroaster in Iran, the Hebrew prophets, and the first Greek philosophers in Ionia. What they share is a turn inward — the question stops being how to placate the gods and becomes how a person should live, addressed to anyone rather than to a king. Judaism supplies the sharpest case: Nebuchadnezzar destroys the Temple in 586 BC and deports Judah's elite, and a religion built around a place and a sacrifice survives without either by becoming scripture, law and study. That is the model every later diaspora religion works from, and it exists because of a defeat.

Persia assembles the first genuinely multi-ethnic empire — from the Aegean to the Indus — and holds it by a method exactly opposite to Assyria's at slot 10: local gods respected, local elites retained, deportees sent home including the Judeans, tribute standardised, satraps supervised by royal inspectors. Tolerance is a logistics decision here, because an empire this size cannot garrison itself. It is the largest and best-administered state the world has yet seen, it is the template Alexander captures intact in era 02, and it is the thing the Greeks of the next era define themselves against.

Athens reorganises citizenship by neighbourhood rather than by clan and invents demokratia — sovereignty exercised directly by an assembly, with most offices filled by lot rather than election, on the reasoning that election favours the well-known and the rich. Rome expels its last king the year before and builds the opposite answer to the same problem: an elected, term-limited, deliberately jammed aristocratic machine designed so that nobody can accumulate enough of it to become a king again. Two experiments in rule without a monarch, begun within a year of each other, and the whole later argument about government is conducted between them.

Marathon in 490 and Salamis in 480: a coalition of small Greek cities defeats the largest empire on earth, twice. Militarily it is a frontier nuisance for Persia; culturally it is the founding event of a Greek self-understanding built on the contrast between citizen-soldiers who choose to fight and subjects who are made to — the East/West opposition enters the world here, as propaganda, and never leaves. Athens converts its share of the victory into a naval empire and spends the proceeds on slot 3.

Thirty years of allied tribute, spent on one city: the Parthenon, the tragedies of Aeschylus, Sophocles and Euripides, Herodotus inventing history as a genre, and a democracy radical enough that ordinary citizens sit on juries of hundreds and are paid to do it. It is the most concentrated cultural output in the record, and it is funded by an empire — the same assembly that perfects self-government votes to destroy Melos for staying neutral. The two facts belong to one hour, because the second is what makes slot 4 happen.

China fragments into seven large states in permanent war, and the competition produces both mass infantry armies with crossbows and iron farming, and the most fertile period of Chinese thought — Mencius developing Confucius, Zhuangzi and the Daoists, Mozi arguing for impartial care, Sunzi on war, and the Legalists arguing that only law and punishment hold a state together. Every subsequent Chinese political argument draws on this menu. The Legalists win the war at slot 11, and the Confucians win the peace in era 03.

Sparta and its allies against the Athenian empire for twenty-seven years, ending Athenian power and exhausting the Greek city-state system that had just defeated Persia. Thucydides writes it up as the first analysis of politics as a system of interests rather than a tale of gods — plague, civil war, the Melian dialogue, the catastrophe at Syracuse — and it is still the standard text on how a rising power and an established one talk themselves into war. The polis peaks and burns out inside a single lifetime, which is what leaves the space for Macedon.

Athens executes Socrates for asking questions, Plato responds by founding a school and arguing that the visible world is a shadow of a real one, and Aristotle responds to him by insisting on classifying the visible world instead. Between them they set the agenda — ethics, logic, politics, metaphysics, biology — that Islamic and Christian thought will both spend two thousand years writing commentaries on. Aristotle then tutors a Macedonian prince, which is the single most consequential teaching job in history and the subject of slot 7.

Alexander takes Persia's empire whole in eleven years, largely by capturing its administration intact rather than destroying it, and dies at 32 leaving his generals to carve it into the Seleucid, Ptolemaic and Antigonid kingdoms. The lasting product is not the conquest but the zone: Greek becomes the working language from Egypt to Afghanistan, cities are founded on a Greek template across it, and Buddhist sculpture in Gandhara starts looking Greek. Rome will conquer this zone in era 03 and be culturally conquered by it in return.

Chandragupta unifies most of the subcontinent in the vacuum Alexander leaves behind, advised — by tradition — by Kautilya, whose Arthashastra is a manual of statecraft as cold as anything Machiavelli wrote eighteen centuries later: spies, famine relief, tax rates, and when to break a treaty. It is the first empire to hold most of India and it runs on a professional bureaucracy rather than on tribute from subordinate kings. Its third ruler is slot 10.

The Ptolemies fund a Library and a Museum in Alexandria with a standing instruction to acquire every book in the world, and the result is the greatest concentration of science before the seventeenth century: Euclid's geometry, Archimedes on levers and floating bodies, Eratosthenes measuring the earth's circumference to within a few per cent using shadows in two cities, Aristarchus proposing a sun-centred cosmos eighteen centuries before Copernicus. Almost none of it is applied — the ancient world has slaves rather than a labour shortage, and therefore no reason to build machines — which is the era's clearest demonstration that knowing how is not the same as having a reason to.

Chandragupta's grandson conquers Kalinga, is appalled at the slaughter, converts to Buddhism, and publishes his remorse on rock edicts across the empire in the local languages — the first state anywhere to advertise non-violence as policy. More consequentially, he becomes the first ruler to sponsor a missionary religion abroad, sending Buddhism to Sri Lanka and toward Central Asia, from where it reaches China in era 03. Buddhism becomes a world religion because a king felt guilty about a war he had won.

The Legalists of slot 4 win: the Qin conquer the warring states and standardise everything at once — script, weights, axle widths, currency, law — while abolishing the feudal nobility in favour of appointed officials, burying dissenting scholars and burning the books that disagree. The dynasty is brutal and lasts fifteen years; the unification lasts to the present, because the standardisation turned China into a single administrative object that later dynasties could simply re-inherit. Compare era 04's fifth hour, where Rome's west fragments and nobody reassembles it for a thousand years.

Three wars with Carthage turn Rome from an Italian power into master of the western Mediterranean, and Hannibal's fifteen years rampaging through Italy without ever taking Rome demonstrates that a republic with deep manpower beats a mercantile empire with a genius. The victory also breaks the winner: the wars fill Italy with slaves and great estates, ruin the smallholders who were the army's whole basis, and set up the century of civil war that era 03 spends its first half on. Carthage is levelled in 146 BC, the same year Rome sacks Corinth — the Hellenistic world of slot 7 changing owner.

The Qin machine of era 02's eleventh hour collapses in fifteen years, and the Han keep every piece of it while swapping Legalist terror for Confucian legitimacy — the combination that governs China for the next two thousand years. The lasting invention is government by examined official: recruitment by written test on a shared canon rather than by birth, which creates a governing class loyal to the texts and the state rather than to a region or a family. Ninety per cent of Chinese still call themselves Han.

Wudi pushes west against the Xiongnu confederation and, in looking for allies, discovers that the Mediterranean world exists and wants silk. Regular caravan trade begins to link Han China, Central Asia, Parthia and Rome, moving not only goods but Buddhism eastward and — as slot 12 shows — epidemics in both directions. Era 05 is what happens when this corridor is opened wide by a single power, and era 06 is what happens when ships make it obsolete.

The prize of era 02's twelfth hour turns out to be poison: conquest fills Italy with slaves and vast estates, the smallholding farmers who filled the legions are ruined, and the army is reformed to recruit the landless — who then look to their general rather than the Senate for land on discharge. Tiberius Gracchus proposes redistribution and is murdered by senators; his brother follows a decade later. Political violence enters Roman practice here and never leaves, and every step from this hour to slot 5 is a general with an army who owes the Senate nothing.

While Eurasia builds its road empires, the Americas build theirs in complete isolation — Teotihuacan in the valley of Mexico grows into a grid-planned city of over 100,000, among the largest in the world, with pyramids, apartment compounds and a reach across Mesoamerica; the Maya cities take their classic form; the Moche and Nazca develop on the Peruvian coast. They do it without the wheel in practical use, without draught animals, and without iron — which is the point. These are not a lesser version of the Old World's story, they are the control experiment for it, and era 06's ninth hour is what happens when the two finally meet.

A republic designed for a city-state cannot govern a Mediterranean empire, because generals with provincial armies and provincial money are stronger than the institutions meant to check them. Caesar proves it, is murdered by senators trying to restore the machine, and the murder produces thirteen more years of civil war rather than a restoration. The lesson every later republic studies is that the constitutional forms were still perfectly intact on the day they stopped meaning anything.

Caesar's heir wins the civil wars and then does the clever thing: he keeps every republican title, office and ritual, calls himself merely first citizen, and holds all the actual power through control of the armies and the treasury. The Roman Empire is a monarchy that never admits to being one, and the pretence is load-bearing for three centuries — until era 04's first hour, when the army works out that it can simply choose. What Augustus buys with it is two hundred years of internal peace, the longest the Mediterranean has ever had.

Three legions are annihilated in a German forest, Augustus abandons the conquest of Germania, and the empire's northern border settles on the Rhine and Danube for the next four centuries. It matters because it is the moment Rome stops expanding, and an empire that has stopped expanding has to pay for itself out of what it already holds rather than out of the next conquest. The line drawn here is also the one that still separates Romance-speaking Europe from German-speaking Europe.

A Jewish preacher is executed in a minor province, and within thirty years Paul has made the decisive move: dropping circumcision and the food laws so that gentiles can join without becoming Jews first. That converts a local reform movement into a religion anyone can enter, travelling on Roman roads, in the Greek that era 02's seventh hour spread, among the urban poor the empire had no other use for. The whole second half of era 04 depends on this hour.

Rome crushes the Jewish revolt and burns the Temple, ending sacrificial Judaism for good; what survives is the rabbinic tradition of text, law and study that the Babylonian exile of era 01 had already prototyped. It also forces the final separation of the Jesus movement from Judaism, since the two now have incompatible answers to what replaced the Temple. Two world religions leave this hour as distinct things, and the argument between them is set for two millennia.

The Kushan empire straddles Afghanistan, Pakistan and north India, sitting astride slot 2's trade road and minting coins with Greek, Persian, Hindu and Buddhist gods on them at once. Under Kanishka it sponsors Mahayana Buddhism and the Gandharan art that gives the Buddha a Greek face, and it is the conduit through which Buddhism reaches China — where it becomes, over the next few centuries, the first foreign idea China ever adopts wholesale. A religion crosses a continent because a trading empire found it useful to be legible to everybody.

Trajan reaches the Persian Gulf and the empire is at its largest — perhaps 60 million people, a single market with one currency, sea lanes clear of pirates, and citizenship extended to almost every free inhabitant by 212. His successor Hadrian immediately gives up the eastern conquests and builds walls, because the empire has passed the point where new provinces pay for the armies needed to hold them. The high point and the moment of turning are within one reign of each other, which is the shape of most imperial peaks.

Plague arrives along slot 2's trade road in 165 and kills perhaps a tenth of the Roman empire; Marcus Aurelius, who writes Stoic philosophy at night on the Danube frontier, dies of it in 180 and leaves his son Commodus. In the same decades Han China is failing from its own epidemics, court paralysis and the Yellow Turban revolt. The two ends of Eurasia crack within a generation of each other, connected by the road that made them both rich, and era 04 is the long consequence at both ends.

Han China breaks into the Three Kingdoms and then nearly four centuries of division, while Rome spends fifty years on more than twenty emperors, almost all murdered, with the currency debased and the frontiers broken. Rome survives by becoming unrecognisable: Diocletian from 284 splits the empire four ways, fixes prices by edict, makes occupations hereditary, doubles the army and turns the emperor from first citizen into a sacred figure approached on the knees. The pretence of era 03's sixth hour is over, and the tax burden required to fund the replacement is a large part of why western provincials eventually stop resisting the new arrivals.

Constantine legalises Christianity, presides over Nicaea in 325 to force a single creed out of a fractious church, and founds Constantinople in 330 — moving the centre of gravity to a defensible, rich, Greek-speaking east that outlives the west by a thousand years. Persecuted sect to imperial religion in one reign, which imports the empire's administrative habits into the church: dioceses, councils, orthodoxy defined and heresy defined alongside it. When the western state fails at slot 5, this apparatus is already in place to inherit its functions, which is the whole premise of the era.

Northern India's classical age, and a lighter kind of empire — the Guptas rule through subordinate kings rather than direct administration and put the surplus into culture and mathematics. The decimal place-value system with a symbol for zero is worked out here, Aryabhata computes π and models a rotating earth, Kalidasa writes, and Hindu temple architecture takes its classical form while Buddhism begins its long decline in the land of its birth. Slot 9's Baghdad takes those numerals and passes them west, and every number in this knowledge base is written in them.

Hunnic pressure on the steppe pushes Gothic peoples to the Danube, where Rome admits them as refugees, mistreats them, and is destroyed by them at Adrianople in 378 — an emperor killed and an eastern field army annihilated. The migrations are usually pictured as invasion but they begin as an asylum crisis handled badly, and by 410 a Gothic general who had served Rome holds the city for three days. It is militarily minor, since the capital had already moved to Ravenna, and psychologically enormous, and Augustine answers it with The City of God, separating the fate of the earthly city from the fate of the church — the intellectual permission slip for Christianity to outlive the empire that adopted it.

The last western emperor is deposed by a Germanic general who does not bother replacing him, because the office had already been hollowed out — the army was federate, the taxes uncollectable, and real power sat with kings keeping Roman law, Roman bureaucrats and Roman titles while ruling in their own names. There is no fall so much as a fade: Visigoths in Spain, Vandals in Africa, Franks under Clovis in Gaul, Ostrogoths in Italy. The Latin church is the only pan-western institution left standing, and for the next six centuries it behaves like one — which is the era's thesis in its purest form.

The east tries to put the empire back together: North Africa and Italy reconquered, Roman law codified into the Corpus that is the basis of most European law today, and Hagia Sophia built in five years. Then bubonic plague arrives in 541 and kills perhaps a quarter to a half of the Mediterranean population, the reconquest becomes unaffordable, Italy is left ruined by twenty years of fighting, and a long war with Persia exhausts both empires. Slot 8 walks into the space those two leave, and it walks in almost unopposed.

The Sui reunite China after 360 years, build the Grand Canal linking the rice-growing south to the northern capitals, and collapse from the effort in two generations — after which the Tang inherit a working state and run the most cosmopolitan empire of the age, with a foreign quarter in Chang'an and Buddhism at its height. The canal is the key artefact: it makes southern food politically usable in the north, which is what makes reunification stick where every earlier attempt failed. Compare slot 5, where nobody reassembled anything for a thousand years — the difference is that China kept its script and its canon through the fragmentation, so there was something to rebuild from.

Muhammad's move to Medina starts the Islamic calendar and turns a preaching movement into a community with law, taxation and an army; within thirty years of his death the Arabs hold the entire Sasanian empire and Byzantium's richest provinces, against two powers that had just exhausted each other at slot 6. The speed is the point — the fastest large-scale change of ownership in the record, and it happens because the incumbents' subjects mostly did not fight for them. Then the succession dispute settles into permanence: Husayn is killed at Karbala in 680, and the Sunni-Shia division becomes a fixed feature rather than a faction fight, still running through Iraq, Iran, the Gulf and Lebanon today.

The Abbasids overthrow the Umayyads on a platform of equality for non-Arab Muslims and found a round city at Baghdad in 762, out of the Mediterranean and into the old Persian world — Islam stops being an Arab conquest elite and becomes a genuinely multi-ethnic civilisation. Under al-Ma'mun it funds the systematic translation of Greek, Persian and Sanskrit science into Arabic and then goes past it: al-Khwarizmi gives his name to the algorithm and his book's title to algebra, and slot 3's Indian numerals are adopted and passed west. Paper, learned from Chinese prisoners at Talas in 751, makes it a public culture rather than a court hobby. Almost everything Europe rediscovers in era 05 comes back through Arabic, which is why so much of it still has an Arabic name.

The Pope crowns Charlemagne emperor on Christmas Day, reviving a western empire vacant since slot 5 and establishing that the church confers legitimacy on kings rather than the reverse; his grandsons then split it three ways at Verdun in 843, and the western and eastern portions become recognisably France and Germany with a contested strip in the middle that stays contested until era 10. In the same centuries the Norse take to boats — raiding west from Lindisfarne in 793, and trading east down the Dnieper and Volga to Byzantium and Baghdad, settling as a ruling layer over Slavic populations with Kyiv at the centre. In 988 Vladimir of Kyiv chooses Byzantine Christianity, and with it Cyrillic letters and Orthodox political theology, fixing a religious frontier through eastern Europe that is legible on any map of the region today.

The Song reunify a smaller, richer, more commercial China — the most advanced economy on earth by a distance, with printing, paper money, the compass, gunpowder, blast-furnace iron at a scale Europe will not match until era 08, and a civil service recruited by examination. They also lose the north and buy peace with tribute, which shows that economic supremacy and military security are different problems. Around them, a bucket for everywhere the usual frame ignores: the Chola dynasty running a naval empire across the Bay of Bengal, Ghana taxing the gold that crosses the Sahara, Cahokia rising on the Mississippi, and a brief Norse landing in Newfoundland. Around the year 1000, western Europe is among the poorer and less organised parts of the world, and nothing about it looks like the future.

Within twenty-five years the religious order that had held the era together splits three ways. Latin and Greek Christianity excommunicate each other in 1054 over papal authority and a clause in the creed, formalising five centuries of drift into two Christendoms that will not reliably help each other. The Investiture Controversy sets Pope against emperor over who appoints bishops, and at Canossa in 1077 an emperor waits three days in the snow — Europe ends up with two competing universal authorities and no single one, which is a large part of why it never unifies. And at Manzikert in 1071 the Seljuks destroy a Byzantine army and take Anatolia, so Byzantium appeals west for mercenaries. Era 05 opens with what actually turns up.

What Byzantium asked for after era 04's last hour was mercenaries; what arrived was an armed migration that took Jerusalem, massacred its population and founded four Latin states on the Levantine coast. Militarily it succeeds only because the Islamic world is fragmented between Seljuks and Fatimids at that exact moment. The lasting effects are commercial and intellectual rather than territorial: Venice, Genoa and Pisa get the shipping contracts and never let go, and Europe acquires a permanent hostile intimacy with a wealthier civilisation.

Europe recovers Aristotle, Euclid, Ptolemy and Galen — mostly translated from Arabic in Toledo and Sicily — and builds an institution to argue about them in: the university, chartered as a self-governing corporation of scholars at Bologna, Paris and Oxford. Roman law is recovered at the same moment and gives kings a professional bureaucracy, while Gothic building from Saint-Denis in 1144 turns the surplus into height and glass. The degree, the faculty, the exam and the lecture are all this hour's inventions, and they are the delivery mechanism for eras 07 and 08.

Saladin unifies Egypt and Syria — the fragmentation that made slot 1 possible is over — and destroys the crusader field army at Hattin, taking Jerusalem back and notably not massacring it. The Third Crusade recovers the coast but not the city, and from here the crusader presence is a commercial coastline on borrowed time. Saladin also becomes the one Muslim ruler European chivalric literature admires, which is its own small evidence that the connection was cultural as well as violent.

A crusade that cannot pay Venice for its shipping is redirected first to a Christian city in Dalmatia and then to Constantinople itself, which it storms, loots for three days and rules for the next fifty-seven. The richest city in Christendom never recovers; Byzantium limps on as a rump until 1453, and the Orthodox world's memory of the Latin west is fixed here. Venice, which engineered it, takes the Aegean and becomes an empire. The schism at era 04's twelfth hour stops being a doctrinal quarrel and becomes an injury.

In the same year a Mongol assembly proclaims Temujin as Genghis Khan, and in north India a Turkic slave-general founds the Delhi Sultanate. Genghis welds the steppe tribes into a meritocratic army with unmatched mobility, discipline and intelligence-gathering, and inside seventy years his family rules from Korea to Hungary — the largest contiguous land empire ever. Delhi, meanwhile, begins six centuries of Muslim rule in north India that make the subcontinent's religious map what it still is.

English barons force a defeated, broke king to accept in writing that the crown is bound by law — due process, no arbitrary imprisonment, no taxation without consent of the realm. It is a feudal document about baronial privilege, immediately repudiated, and it matters anyway because it is written: a text later centuries can quote back at power, which is exactly what era 07's eighth hour and era 08's third do. Compare era 01's sixth hour, where the same move was made in stone for the same reason.

Hulagu takes Baghdad, executes the last Abbasid caliph, and destroys the libraries and the irrigation works of Mesopotamia — the Tigris is said to have run black with ink. The caliphate as a single centre of Islamic authority ends here permanently, and the Islamic world's intellectual centre of gravity shifts to Cairo, Persia and later Istanbul. The Mongols are checked in Egypt by the Mamluks at Ain Jalut in 1260, and their westward run stops for good.

Kublai proclaims the Yuan dynasty and completes the conquest of Song China, and for roughly a century one political authority holds the road from Korea to the Black Sea — safe enough, the saying went, for a virgin with a pot of gold to walk it. Marco Polo travels it, Persian astronomers work in Beijing and Chinese engineers in Persia, and printing, gunpowder and the compass move west. This is the most connected the pre-oceanic world ever gets, and slot 11 is the bill for it.

The last crusader city on the mainland is taken and the two-century Latin presence in the Levant ends, leaving Europe's relationship with the east permanently commercial rather than territorial. Italian merchants keep the trade and lose the excuse, the military orders relocate — the Templars into destruction in 1307, the Hospitallers to Rhodes and eventually Malta — and the crusading impulse looks for other targets, finding Iberia and the Baltic. The search for a route to Asian goods that does not pay Venetian and Mamluk tolls starts here, and pays off in era 06.

The ruler of Mali crosses to Mecca with a caravan so laden with gold that his spending is said to have depressed Egyptian prices for a decade — and Europe, which had been paying for that gold without knowing where it came from, puts Mali on its maps for the first time. Mali runs the trans-Saharan trade in gold, salt and slaves and endows Timbuktu as a centre of Islamic scholarship. The relevant fact for the spine is that the richest documented individual of the medieval world was a west African, and Europe found out by accident.

Plague travels slot 8's roads and slot 1's shipping lanes from Central Asia to Crimea to Messina, and kills perhaps a third to a half of Europe in four years, with comparable losses across the Islamic world and probably China. The demographic shock breaks serfdom in western Europe by making labour scarce and wages high, discredits both medicine and the church that failed to explain it, and triggers the massacre of Jewish communities blamed for it. The connection that made the era is what ends it, which is why the era is named for the connection rather than for any of its beneficiaries.

The Ming expel the Yuan and rebuild a Chinese empire that is deliberately agrarian, inward-facing and suspicious of the steppe, while Timur's conquests from Samarkand wreck what is left of the central Asian trade cities. The corridor closes at both ends within a generation, land routes east become expensive and dangerous, and Europe's alternative — go round by sea — becomes worth the enormous risk. Era 07 opens with two fleets, one Chinese and one Portuguese, and only one of them keeps going.

The Ming send seven vast expeditions across the Indian Ocean to Africa — hundreds of ships, some four times the length of anything European, carrying tens of thousands of men. They are diplomacy and prestige rather than conquest or trade, and after 1433 the court cancels them, burns the records and bans ocean-going shipbuilding, because the mandarins judged the northern frontier the real problem and the eunuch admirals' project a waste. The most capable maritime power on earth withdraws from the ocean seventy years before Portugal reaches India, and the era is the story of what happened in the space it left.

Portugal takes Ceuta in Morocco and then works south for eighty years, a cape at a time, driven by the search for a sea route to slot 10 of era 05's gold and to Asian spices without Venetian and Ottoman middlemen. The enabling kit is the caravel, the compass, the astrolabe and the accumulated knowledge of Atlantic wind systems — the return leg only works if you sail out into the empty ocean and loop back. Sugar plantations on Madeira and São Tomé, worked by enslaved Africans, are prototyped in these decades: the Atlantic system is invented before the Atlantic is crossed.

Movable metal type, an oil-based ink and a screw press combine into a machine that drops the cost of a book by orders of magnitude — by 1500 there are millions of printed books in Europe where there had been tens of thousands of manuscripts. China had printing centuries earlier but with tens of thousands of characters the economics of movable type never worked; an alphabet of two dozen letters is what makes the machine pay. Era 02's cheap writing made literacy possible; this makes it cheap to be argued with, and slot 7 is the first demonstration.

Mehmed II takes the city with the largest cannon yet built, ending the Roman Empire 1,480 years after Augustus and turning the Ottomans into the dominant power of the eastern Mediterranean. Cannon of that scale make the tall medieval wall obsolete overnight, which reshapes European fortification and, with it, the cost of war — the beginning of the fiscal spiral that produces era 07's tax state. Greek scholars and manuscripts move west into Italy, feeding the Renaissance, and Moscow starts calling itself the third Rome.

Three things in one year: Granada falls and eight centuries of Muslim rule in Iberia end, Spain expels its Jews, and Columbus sails west on a serious underestimate of the earth's size and lands in the Caribbean convinced it is Asia. The connection is causal — the crusade in Spain finishes and releases both the money and the appetite for the next one. What follows is the Columbian Exchange: maize, potatoes and tomatoes east; wheat, horses, cattle, sugar and smallpox west.

Portugal completes the eighty-year project of slot 2 and arrives in Calicut, into an Indian Ocean trade world that was old, rich, multi-religious and largely unarmed at sea. The Portuguese contribution is to arm it: cannon on ships, forts at chokepoints — Goa, Hormuz, Malacca — and a licence system charging others to use waters they had used freely for centuries. Europe does not out-trade Asia in this era or the next; it inserts itself as an armed toll collector, and that is the template for the next four hundred years.

An Augustinian monk objects to the sale of indulgences, and the objection — instead of being contained as a hundred earlier ones were — is printed, translated and distributed across Germany within weeks. The doctrine that matters is scripture alone and faith alone, which removes the priesthood's monopoly on salvation and, with vernacular printed Bibles, hands interpretation to anyone who can read. German princes adopt it partly out of conviction and substantially because it lets them seize church land, which is why the religious map of Europe ends up matching the political one.

The Ottoman empire under Suleiman the Magnificent holds the Balkans, Anatolia, the Levant, Egypt, Iraq and the north African coast, takes Belgrade and Rhodes, crushes Hungary at Mohács in 1526 and besieges Vienna in 1529. It is the era's most formidable state by a distance — better financed, better administered and more religiously tolerant of its minorities than its Christian rivals — and its pressure is a permanent factor in European politics, including the reason the Habsburgs could never crush slot 7's Protestants. Safavid Persia, Shia and hostile, is the other half of the story: the Sunni–Shia line of era 04 becomes a state border here.

Cortés takes Tenochtitlan — a city larger than any in Spain — with a few hundred Spaniards, tens of thousands of indigenous allies who hated Aztec tribute, and smallpox; Pizarro repeats it against an Inca empire already gutted by epidemic and civil war by 1533. Disease is the decisive factor: with no exposure to Eurasian crowd diseases, the population of the Americas falls by something like 90 per cent within a century, the largest demographic catastrophe in the record. The labour vacuum that follows is what the Atlantic slave trade is built to fill.

A Timurid prince from Central Asia wins at Panipat with field artillery and mobile cavalry, and his dynasty goes on to rule most of the subcontinent for two centuries — under Akbar with a deliberate policy of religious pluralism, abolishing the tax on non-Muslims and staffing the state with Hindus. At its height Mughal India is around a quarter of world manufacturing output, the source of the cotton textiles that everyone else wants and the target that eras 08 and 09 organise around. Gunpowder empires — Ottoman, Safavid, Mughal, and in era 07 the Qing — are the era's dominant state form, and none of them are European.

In 1543 Copernicus puts the sun at the centre and Vesalius publishes human anatomy from actual dissection rather than from Galen — two books that say, in different fields, that the authorities were wrong and observation says so. Two years later Spain finds a mountain of silver at Potosí, and the resulting flood of bullion pays for Habsburg wars, causes a century of inflation in Europe, and ends up mostly in China, which had monetised its economy in silver and would sell anything for it. The first true global economy is a loop from a Bolivian mine to a Chinese warehouse, and Europe's role in it is carrier and customer.

Spain's invasion fleet is broken by English ships, Dutch shallow-water tactics and weather, and although the war drags on for fifteen more years the strategic point is made: the Atlantic seaboard powers can resist the silver empire of slot 11. The Dutch revolt against Spain matures into an independent republic that is commercial, Calvinist, tolerant enough to attract capital and refugees, and about to invent the joint-stock company and the stock exchange. Economic gravity moves from the Mediterranean to the North Sea, and era 07 opens there.

The English East India Company is chartered in 1600 and the Dutch VOC in 1602, and the VOC is the genuinely new thing: permanent transferable shares, a stock exchange to trade them on, and a state grant of the right to make war, sign treaties and hold territory. This is a corporation with sovereign powers, invented because Asian trade needed more capital and carried more risk than any merchant or king could bear alone. It is how Europe ends up governing much of Asia — not by royal conquest but by shareholders, and era 09's second hour is where a government finally takes the job back.

Moons round Jupiter, phases of Venus, mountains on a supposedly perfect moon — observations that Copernicus's model at era 06's eleventh hour predicted and the accepted one did not. Galileo publishes in Italian rather than Latin, deliberately arguing in public, and is condemned in 1633 for it; the trial does not stop the method, it moves its centre north to Protestant countries and to France. The method is the invention here: a claim about the world is settled by looking, by anyone who repeats the look, and no authority is exempt.

A Bohemian revolt becomes a general European war fought mainly in Germany, killing perhaps a third of its population — the worst demographic catastrophe in German history until era 10. It begins as a religious war and ends as a dynastic one, with Catholic France funding Protestant Sweden against Catholic Habsburgs, which is the moment everyone can see that religion has stopped being the organising principle. The exhaustion is the necessary condition for slot 5: sovereignty is what you agree to when you have proved you cannot convert each other.

Manchu armies enter Beijing after peasant rebellion and famine have already destroyed the Ming, and go on to build the largest and richest empire China has ever had — doubling its territory into Tibet, Xinjiang and Mongolia, and tripling its population. The 1640s convulse almost everywhere at once: Ming collapse, English civil war, revolts against Spain in Catalonia and Portugal, France's Fronde, an Ottoman crisis — during the coldest decades of the Little Ice Age, with harvest failure the common factor. It is the clearest case on the spine of climate as a political input.

The peace ending slot 3 settles that a ruler determines the religion of their own territory and that no outside authority — Pope or emperor — may intervene in it, and it does the settling by a congress of states negotiating as legal equals. That package is what "sovereignty" means: a bounded territory, one supreme authority inside it, formal equality between them however unequal in fact, and diplomacy as the way they deal with each other. Every later international order, including the UN at era 10's last hour, is an argument with this one.

Parliament defeats the king in a civil war and then tries and executes him in public, on the argument that a king who breaks his contract with the people may be judged by them — a claim no European monarchy had faced and every one of them noticed. The republic fails, the monarchy returns in 1660, and the underlying question of who is finally sovereign, crown or parliament, is left to slot 8. Hobbes writes Leviathan out of the terror of it, Locke writes his answer out of the sequel, and era 08's third and fourth hours quote Locke.

One set of mathematical laws governs the fall of an apple and the orbit of the moon — the heavens and the earth turn out to run on the same rules, and those rules can be written down and used to predict. It is the payoff of slot 2's method and the most consequential book of the era, because it establishes that the universe is legible: the Enlightenment's confidence that reason can reorder politics and society is Newton's success generalised, probably further than it deserved. Every hour of era 08 is being argued by people who believe the world is a mechanism that can be understood and therefore improved.

Parliament replaces one king with another on its own terms, settles the question of slot 6 in parliament's favour, and in 1694 charters a bank to lend the state money at interest against tax revenue guaranteed by that same parliament. That is the fiscal-military state: because the lenders control the taxes, the debt is credible, so it is cheap, so a middling country can outspend France for a century. Britain wins era 08's first hour on this financial machinery rather than on population or army size, and everything downstream of that debt is the rest of era 08.

Fifty years of expansion and of reversing Akbar's religious pluralism leave the empire overextended and its Hindu subjects alienated; within decades of Aurangzeb's death the Marathas, the Sikhs, Bengal, Hyderabad and Awadh are effectively independent and Delhi is sacked by Persia in 1739. The richest state in the world becomes a set of competing successor states with modern armies that need financing — which is precisely the opening a chartered company with slot 8's credit can walk into. Plassey in 1757 belongs to era 08's first hour, and this is why it was possible.

Peter the Great fights Sweden for twenty-one years to reach the Baltic, wins at Poltava in 1709, and builds St Petersburg on captured marsh as a deliberate window on Europe — importing shipwrights, engineers, taxes, conscription and a shaved-beard dress code by decree. Russia becomes a European great power in a single reign, by autocratic modernisation from above rather than by anything growing from below. It is the first of the reform-or-be-eaten programmes that Japan runs at era 09's fifth hour and China fails to run at its twelfth.

The peace ending the War of the Spanish Succession codifies the balance of power as an explicit principle — no state may become strong enough to dominate — and hands Britain the asiento, the contract to supply enslaved Africans to Spanish America. That is the era's two halves in one treaty: a rational, secular, treaty-managed states system, financed by the largest forced migration in history. Roughly 12 million people are shipped across the Atlantic in total, most of them in this era and the next, and the sugar, tobacco and cotton they produce are the capital era 08 industrialises with.

Frederick the Great seizes Silesia from Maria Theresa in the year he inherits Prussia, starting a rivalry that structures central Europe until 1866, and both then reform hard — codified law, professional bureaucracy, religious toleration, state schooling — because a state that cannot mobilise its people loses. Meanwhile Diderot's Encyclopédie sets out to put all knowledge in one work, on the assumption that publishing it is itself a political act. Reason applied by the state from above is the era's closing settlement, and era 08 opens by discovering that reason applied from below says something different.

The first genuinely global war — fought in Europe, North America, the Caribbean, West Africa and India. Britain wins Canada and effective control of Bengal, becoming the dominant maritime empire. Both winner and loser end enormously in debt, and that debt is the fuse for slots 3 and 4.

Coal, steam and cotton compound: cheap energy makes cheap cloth, cheap cloth funds more machinery. Britain has the coal, the capital from slot 1, and the legal framework. This is the era's economic engine and it runs underneath every other slot.

Britain tries to make the colonies pay for slot 1 and the colonies refuse. The break matters less for the territory than for the claim: that legitimate government derives from the consent of the governed, written down and successfully defended. It becomes the template every later independence movement cites.

France is bankrupt from slot 1 and from funding slot 3. Calling the Estates-General to fix the finances instead reopens the question of who rules, and within months the Bastille falls and feudal privilege is abolished — the nation, not the king, becomes the unit of sovereignty. Then invasion and internal revolt turn it into emergency government: the Committee of Public Safety, mass conscription, and tens of thousands executed in the Terror of 1793. Both halves belong to this one hour, because the lesson later revolutions take from it, in both directions, is that a revolution defending itself becomes something else.

Enslaved people in France's richest colony take the Declaration of the Rights of Man literally. The only large-scale slave revolt in history to found a state, independent in 1804 — and the reason the revolutionary claim could not be quarantined to Europeans. France's response, and the indemnity it later extracted, shape Haiti to this day.

The coup of 18 Brumaire ends the Republic's parliamentary phase. Napoleon keeps the revolution's administrative content — legal equality, the Civil Code, careers open to talent, metric measures — and discards its politics. That combination is what actually exports across Europe.

The same year runs both ways: the revolution's heir takes a crown in Paris while the revolution's most literal reading founds a black republic in the Caribbean. Napoleon takes the crown from the Pope's hands to signal that legitimacy now comes from the nation, not the Church.

Napoleon deposing the Spanish king removes the legitimacy the colonies were governed by, and creoles govern in the king's name until they stop bothering. Bolivar and San Martin convert the vacuum into a continent of republics by the mid-1820s — the largest transfer of sovereignty in the era.

The settlement tries to put the era back in its box — restore legitimate monarchies, balance the powers, suppress nationalism and liberalism. It succeeds at preventing a general European war for a century, and fails completely at suppressing the ideas, which resurface at slot 12.

Britain abolishes slavery across most of the empire, having ended the slave trade in 1807. Driven by evangelical campaigning, slave resistance across the Caribbean, and the fact that industrial Britain no longer needed the plantation model as badly. Compensation went to the owners, not the enslaved — a debt Britain finished paying in 2015.

Britain runs a large trade deficit with China, closes it by selling Indian opium into a market where it is banned, and when Beijing destroys the stock at Canton, goes to war over the right to keep selling. China loses comprehensively to steam gunboats, cedes Hong Kong and opens five treaty ports on terms it did not negotiate — the first of the unequal treaties, and the start of what China still calls the century of humiliation. This is the hour where slot 2's industrial advantage is first cashed in as force against the state that had been the world's largest economy, and era 09's twelfth hour follows from it.

Revolutions across France, the German and Italian states, Austria and Hungary, on demands for constitutions, national self-determination and suffrage. Almost all are defeated within eighteen months. But the demands do not go away — they are absorbed by states and delivered from above in era 09, which is why unification happens by Bismarck rather than by barricade.

Britain displays the industrial world to itself in a building made of glass and iron, at the moment it produces something like half the world's manufactured goods. In the same years China is torn apart by the Taiping Rebellion — a Christian-influenced millenarian movement whose suppression kills perhaps twenty million people, more than any other nineteenth-century event, and leaves the Qing dependent on provincial armies it cannot control. The two hours of the same clock: the industrial core showing off, and the largest state on earth being broken by pressures that industry helped create.

A mutiny in the Company's own sepoy army becomes a widespread revolt across north India, is suppressed with great brutality, and ends the East India Company: the Crown takes direct rule in 1858, and era 07's first hour finally closes. Colonial policy afterwards is defensive and racialised — fewer reforms, more separation, government by classification of communities — and the memory becomes the founding grievance of Indian nationalism. Britain also stops pretending its Indian empire is a commercial accident.

Natural selection explains the design of living things without a designer, which is the era's deepest shock to the picture of the world — and, unlike Newton at era 07's seventh hour, it puts humans inside the mechanism rather than above it. Within a generation it is being misapplied to societies and races as social Darwinism, supplying the scientific-sounding vocabulary that slot 8's empire-building and era 10's racial ideologies both use. A theory about finches becomes an alibi for conquest, which is worth holding onto as a case study in how ideas travel.

The United States fights the largest war of the century over whether slavery expands, and settles it at 600,000 dead — abolishing slavery and, in the amendments that follow, writing equal protection into the constitution before spending a century not honouring it. In the same year Russia emancipates 23 million serfs, from above and with the land debt loaded onto the peasants, because defeat in the Crimea had proved a serf economy could not sustain a modern army. Two vast systems of unfree labour end within months of each other, one by war and one by decree, and both leave the freed population poor and constrained.

Confronted by American gunboats in 1853, Japan concludes the alternative is colonisation, overthrows the shogunate, and rebuilds itself deliberately from foreign models — Prussian army and constitution, British navy, French law, American schooling — while abolishing the samurai class that had staged the coup. Inside thirty years it defeats China; inside forty, Russia. It is the one case in the era of a non-western state taking the industrial-national package on its own terms and joining the club rather than being carved up, and slot 11 is the moment everyone else notices.

Bismarck makes a German empire in three short engineered wars — against Denmark, Austria and France — and has it proclaimed in the Hall of Mirrors at Versailles, which guarantees the French will want it back. This is era 08's twelfth hour delivered from above: the nation the 1848 liberals failed to build, handed down by a conservative Prussian state on condition that it stays conservative. It creates at a stroke the strongest industrial and military power on the continent in the middle of it, and every alliance in Europe for the next forty years is a response to that fact.

A second industrial wave built on steel, chemicals, oil and electricity, and — unlike era 08's — on applied science rather than tinkering, with corporate laboratories, engineering degrees and cartels. Germany and the United States lead it and pass Britain, because industrial chemistry and electrical engineering reward systematic training over craft advantage. The telegraph, refrigerated shipping and the steamship also collapse distance: a world grain market and a world price appear, which is why this is the first era with a genuinely global economy in the modern sense.

European powers meet in Berlin to agree the rules for partitioning a continent none of them substantially occupied, and in twenty years take all of it but Ethiopia and Liberia — enabled by quinine against malaria, the machine gun, the steamship and the telegraph. The borders are drawn for European convenience across a thousand polities, and the extraction is at its most murderous in Leopold's Congo, where the death toll runs into millions. The scramble is also a European rivalry exported: the powers grab partly to deny each other, which is the same logic that goes fatal at slot 12.

The Indian National Congress is founded, and comparable movements follow across the empires — Egyptian, Vietnamese, Filipino, Irish, and pan-African congresses from 1900. The decisive move is that they claim the coloniser's own principles: nation, constitution, self-determination and the rule of law, argued in the metropole's language and against its own stated ideals. Empire had exported the national idea along with the railways, and this hour is where the export starts being turned around — the whole of era 11's first decade is the delivery.

The United States destroys Spain's fleet in ten weeks and takes the Philippines, Puerto Rico and Guam, annexing Hawaii the same year, then fights a three-year war against the Filipinos who thought they were being liberated. A country founded in era 08's third hour on anti-colonial principle acquires overseas colonies, and the argument it has with itself about that is the beginning of a permanent American ambivalence about power. In the same years the powers carve spheres of influence out of China, and the Boxer Rising against them is crushed by an eight-nation expedition in 1900.

Japan destroys the Russian fleet at Tsushima and wins the war on land, the first time in the modern era that an Asian power defeats a European one in a full war — and the news electrifies nationalists from Cairo to Calcutta to Hanoi, because it proves the hierarchy is not natural. Russia's defeat triggers the 1905 revolution at home, forcing a constitution and a parliament that satisfy nobody and rehearse 1917. Both halves of this hour are dress rehearsals: one for decolonisation, one for the Russian Revolution.

China's imperial system ends after 2,100 years — the Qing abdicate, a republic is proclaimed, and it immediately fragments into warlordism, leaving the question of what replaces the dynastic state open until 1949. In Europe, the machinery assembled to manage the rivalry of slots 6 and 8 — two alliance blocs, mobilisation timetables measured in days, a naval arms race, and general staffs with plans that only work if executed first — turns a Balkan assassination in 1914 into a continental war in five weeks. Nobody chose it and everybody built it.

Everyone expects a short war of movement and gets four years of trench deadlock, because era 09's industry supplied machine guns, quick-firing artillery, barbed wire and railways — all of which favour the defender — before it supplied anything that could restore movement. The result is casualties on an unimaginable scale for negligible ground, and the mismatch between what the soldiers experience and what the propaganda says is the source of the century's disillusionment. The empires all assume they will win by Christmas; four of them do not exist by the end.

Verdun and the Somme cost over a million casualties between them and settle nothing, which forces the war into everything else: rationing, conscription, censorship, women in the factories, war economies run by the state, and colonial troops and labourers shipped in by the million. In the same year Britain and France secretly agree the Sykes-Picot partition of Ottoman territory, while separately promising Arab independence and, in 1917, a Jewish national home. The modern Middle East's borders and its two irreconcilable promises are made here, and era 11's second and ninth hours are the bill.

The war destroys the tsarist state; a provisional government fails because it keeps fighting; and the Bolsheviks — a small, disciplined party with a slogan of peace, land and bread — take power in October and hold it through a civil war. It is the first state founded on an explicit theory of history, committed to spreading itself, and it makes class revolution a permanent factor in every other country's politics for the next seventy years. The United States enters the war the same year, and the two powers that will run era 11 both step onto the stage in 1917.

The settlement blames Germany, charges it reparations it cannot pay, redraws central Europe into national states that all contain minorities, and applies Wilson's self-determination to Europeans while denying it to everyone else — which produces the May Fourth movement in China, radicalises Ho Chi Minh in Paris, and hands the colonised world its clearest evidence yet of a double standard. The influenza pandemic of 1918-19 kills more people than the war did, in a world too exhausted to record it properly. A peace that satisfies nobody, guarded by a League the United States refuses to join.

Mussolini's march on Rome brings to power the era's political invention — a mass movement built on national humiliation, contempt for parliaments, a cult of the leader and organised street violence, offering itself as the answer to communism and being funded accordingly. In the same year the Ottoman sultanate is abolished, and Atatürk builds a secular Turkish nation-state out of the remnant, complete with alphabet reform and a compulsory population exchange with Greece. Two models for a post-imperial world, and both prove exportable.

A speculative bubble bursts in New York, and because the gold standard and the war debts had chained the world's economies together, it transmits everywhere — world trade falls by roughly two thirds, a quarter of the workforce is unemployed in Germany and the United States, and the orthodox response of balanced budgets makes it worse. The liberal economic order loses its claim to competence, and everywhere the movements offering to replace it with a directed economy gain. This is the hinge of the era: without it, slot 7 does not happen.

Hitler is appointed chancellor in January and has dictatorial powers within two months, on a programme of national revival, rearmament and the elimination of Jews from German life. Roosevelt is inaugurated in March and answers the same depression with the New Deal: public works, banking regulation, social security and the argument that democracy can deliver material security without abandoning consent. Stalin, meanwhile, is starving several million Ukrainians in the course of collectivisation. Three answers to one economic catastrophe, and the rest of the era is the argument between them settled by force.

Japan invades China proper, takes Nanjing and massacres its population, and begins eight years of war that tie down most of the Japanese army and kill perhaps fifteen million Chinese — a fact usually lost when the Second World War is dated from 1939. Japan's motive is resources for an industrial economy without them, which is also why it eventually turns south toward oil and into the United States at slot 10. Meanwhile Spain's civil war from 1936 serves as the European rehearsal, with German and Italian aircraft, Soviet advisers, and Guernica demonstrating what bombing cities does.

Appeasement having conceded Austria and Czechoslovakia, Hitler removes the last obstacle by agreeing with Stalin to divide eastern Europe, and invades Poland on 1 September; Britain and France declare war and cannot help. The blitzkrieg combination of tanks, aircraft and radio restores the movement that slot 1 lacked, and France falls in six weeks in 1940 — the shock that makes the rest of the era possible. Britain holds through the air battle and the Atlantic, alone in Europe, for a year.

Germany invades the Soviet Union in June, which is where the war is decided: four fifths of German casualties are on that front, and the eastern war is fought as a war of annihilation from the start. Japan attacks Pearl Harbor in December, bringing in the industrial power that ends up out-producing everyone combined. And behind the front, the Holocaust moves from shooting to industrialised murder — six million Jews and millions of Roma, Poles, Soviet prisoners and disabled people killed by a bureaucratic system using timetables, ledgers and factories. Era 10's organising capacity, aimed at extermination.

Within six months the war turns on both sides of the world: Midway in June destroys four Japanese carriers and ends the Pacific initiative, and Stalingrad from August to February destroys an entire German army and ends the eastern one. From here the outcome is decided and only the cost is not, and the cost is enormous — the Soviet Union loses around 27 million people, more than every other combatant in Europe together. El Alamein in the same autumn secures the Mediterranean, and the Allies begin arguing about the peace three years before it arrives.

Germany surrenders in May, the camps are opened, and Yalta and Potsdam divide Europe along the line the armies stopped on; in August two atomic bombs end the Pacific war and inaugurate a world where great powers cannot fight each other directly without ending themselves. The wreckage is the starting condition for era 11: two superpowers and no third, a devastated Europe, exhausted colonial empires facing movements that fought for them and now expect payment, and a new set of institutions — UN, IMF, World Bank, and Nuremberg's principle that following orders is not a defence — built by people determined not to repeat era 08's twelfth hour or slot 4 of this one.

India and Pakistan become independent in August, and the partition displaces perhaps fifteen million people and kills between one and two million in a few weeks — the largest migration in history, and the standing demonstration of how badly a hurried decolonisation can go. In the same year the Truman Doctrine and the Marshall Plan commit the United States to containing Soviet power and rebuilding western Europe as a viable alternative, and Bell Labs demonstrates the transistor. Decolonisation, the Cold War and computing all start their clocks within twelve months of each other.

Israel declares independence as the British mandate ends; the war that follows creates the state and displaces around 750,000 Palestinians, and the conflict is still the region's organising fact — the two irreconcilable promises made at era 10's second hour coming due. In the same year South Africa's National Party takes power and legislates apartheid, Britain opens the National Health Service as western Europe builds the welfare states that are its answer to both fascism and communism, and Stalin blockades Berlin, which the airlift defeats and which produces NATO the following year. Four different answers to what a state owes the people inside it, all in twelve months.

The Communists take China after twenty-two years of civil war interrupted by Japan, bringing a fifth of humanity into the socialist bloc and settling the question left open at era 09's twelfth hour; the Soviet Union tests its atomic bomb the same year, ending the American monopoly. Korea follows within a year and establishes the template that holds for forty years: the superpowers arm and supply clients, the fighting is ferocious and local, the front ends up roughly where it started, and neither principal crosses the nuclear line. Mao's own rule then costs tens of millions of lives in the Great Leap Forward's famine and the Cultural Revolution.

Twenty-nine newly independent Asian and African states meet in Indonesia and refuse the choice they are being offered, asserting a third position built on anti-colonialism, sovereign equality and economic development. Nehru, Sukarno, Nasser, Zhou Enlai and later Tito make non-alignment a bloc of its own, and it becomes the majority of the UN General Assembly within fifteen years. It rarely gets what it asks for, and it permanently changes what international politics is about — the agenda stops being purely European and starts including development, racial equality and the terms of trade.

Britain and France conspire with Israel to seize the Suez Canal from Nasser and are forced into humiliating withdrawal by American financial pressure — the moment the old imperial powers learn in public that they are no longer independent powers, which accelerates every remaining independence movement. In the same weeks Soviet tanks crush the Hungarian uprising while the west does nothing, establishing the reciprocal rule that neither superpower intervenes inside the other's sphere. The two events together define the actual rules of the Cold War better than any treaty does.

A Soviet satellite the size of a beach ball crosses the American sky every ninety minutes, and the shock reorganises the West — crash programmes in science education, the founding of NASA and of the agency that later builds the internet, and a decade-long contest that puts men on the moon in 1969. The strategic content is that a rocket which reaches orbit can reach any city on earth, so the space race is the missile race with a friendlier face. It is also the clearest case in the era of superpower rivalry producing something both sides genuinely wanted anyway.

Seventeen African states become independent in a single year, and by 1970 the European empires are essentially gone — the fastest transfer of formal sovereignty in history, carrying era 09's colonial borders forward intact and leaving new states with extractive economies, thin institutions and boundaries drawn for somebody else's convenience. The Congo crisis begins within weeks and shows the pattern that follows: independence, superpower interference, coup. In the same year the contraceptive pill is approved in the United States, which changes how most people actually live at least as much as anything else on this face.

Soviet missiles in Cuba bring the superpowers within days of nuclear war, and the climb-down — a public American concession on invading Cuba, a private one on missiles in Turkey — proves that neither will actually go over the edge. What follows is the hotline, the test ban treaty and the whole arms control apparatus: mutual assured destruction converted from a terror into a management system. This is the single most important structural fact of the era, because it is the reason the two strongest powers in history never fought each other.

Prague's reform experiment is crushed by Soviet tanks; Paris nearly brings down the French government in a student revolt and general strike; the Tet offensive convinces Americans the Vietnam war cannot be won even as it fails militarily; Martin Luther King and Robert Kennedy are assassinated; Mexico City shoots its students before the Olympics. The common element is a generation raised in postwar prosperity rejecting the authority of the institutions that delivered it — on race, war, sex, hierarchy and law. Almost every political demand loses and almost every cultural one wins, which is why the year matters more in retrospect than it did at the time.

Nixon ends the dollar's convertibility to gold and the Bretton Woods system of fixed exchange rates collapses; the 1973 oil embargo quadruples the oil price and produces a stagflation that Keynesian policy has no answer to, ending the long postwar boom. Underneath, two quieter changes are doing more: the shipping container makes freight so cheap that production can be moved anywhere on earth, and Intel ships the first microprocessor in 1971. Apollo 11 lands in 1969 and turns out to be the decade's least consequential technical achievement. The machinery of globalisation and of computing is in place before anyone has a name for either.

Iran's revolution replaces a westernising monarchy with an Islamic republic and puts political Islam on the board as a force that is neither capitalist nor communist, while the Soviet invasion of Afghanistan in December produces the jihad that comes back at era 12's seventh hour. In the same eighteen months Thatcher takes office and Reagan follows, launching the market-liberal turn of privatisation, deregulation and defeated unions. And Deng Xiaoping begins the reforms that take China from famine to the world's factory in thirty years. Three programmes for what comes after the postwar consensus, and the largest of them by far is the Chinese one.

A Soviet economy that cannot feed itself, afford Afghanistan or match American military spending gets a reformer who tries glasnost and perestroika to fix it — and finds that an unfree system cannot be half-opened. Solidarity in Poland has already shown from 1980 that a workers' movement can oppose a workers' state; Chernobyl in 1986 demonstrates what the secrecy costs; and in 1988 Gorbachev renounces the doctrine that justified the tanks of slots 5 and 9. Once eastern Europe understands the tanks are not coming, the whole structure has about a year left.

The Berlin Wall opens in November and the eastern bloc dissolves within two years — an empire lost without a war, because Gorbachev refused to use the tanks. In June of the same year China's leadership makes the opposite choice at Tiananmen and survives, which sets the era's defining question of whether prosperity requires consent, and thirty years of Chinese growth make the answer much less obvious than it looked in 1989. And at CERN Tim Berners-Lee proposes the World Wide Web, which is the other thing this year did to the world.

A failed coup by hardliners finishes what it meant to prevent, and the USSR dissolves into fifteen states in December, leaving Russia with the debts, the nuclear weapons and a decade of catastrophic economic collapse. The United States is briefly the only superpower, and the first Gulf War is fought as a demonstration of what that means — a UN mandate, a coalition, and overwhelming precision force. India, meanwhile, responds to a balance-of-payments crisis by dismantling its licence economy, which sets a sixth of humanity on a different trajectory with far less commentary.

Maastricht turns the European Community into the European Union with a common currency planned, NAFTA follows in 1994, and the WTO replaces the old trade rules in 1995 with a court that can enforce them. The theory is explicit and confidently held: open markets produce prosperity, prosperity produces a middle class, and a middle class produces liberal democracy — so integration is a one-way ratchet toward convergence. Most of the rest of this face is the testing of that proposition, and it does not survive intact.

South Africa holds its first universal election and Nelson Mandela — twenty-seven years in prison — becomes president, choosing negotiated transition and a truth commission over retribution, which is the single most successful political act of the decade. In the same hundred days, roughly 800,000 Rwandans are murdered by their neighbours while a UN force is withdrawn and the major powers avoid the word genocide precisely because using it would have obliged them to act. Two answers to what a divided society does with its past, in the same year, on the same continent — and the second is the one that shaped the doctrine of intervention for the next twenty years.

The web escapes the universities: graphical browsers, Windows 95, Amazon and eBay founded, and a wave of investment that becomes the dot-com bubble and bursts in 2000 without slowing the underlying build-out. The infrastructure laid in these years — undersea cable, search, the protocols nobody owns — is what every later hour on this face runs on. It arrives with a confident politics attached, that a network with no centre cannot be censored and will therefore dissolve authoritarian government, and slot 11 is where that gets tested.

Three signals in one year that the ratchet of slot 3 has edges. The Asian financial crisis wrecks the fastest-growing economies on earth in months through capital flight, and the conditions imposed for rescue leave a durable resentment of the western financial institutions. Hong Kong returns to China under one country, two systems — a bet that integration would liberalise China rather than the reverse. And the Kyoto Protocol is the first binding attempt to treat the atmosphere as a shared object, immediately exposing the problem that no sovereign state can be made to sign.

Al-Qaeda attacks New York and Washington, and the American response — Afghanistan, then Iraq in 2003 on false premises — consumes two decades, trillions of dollars and most of the goodwill the end of the Cold War produced, while normalising mass surveillance at home. In December of the same year China joins the World Trade Organization, which does far more to reshape the world: manufacturing relocates on a scale that hollows out industrial regions across the west and lifts hundreds of millions out of poverty in Asia. The politics of the 2000s were about the first event and the economics were about the second, and almost nobody said so at the time.

The invasion of Iraq is launched without a UN mandate against the opposition of most of the world, and the insurgency, sectarian war and eventual rise of Islamic State that follow become the standing argument against the idea that political orders can be installed from outside. In the same spring the Human Genome Project is completed, thirteen years and three billion dollars for the first read of the human instruction set — a cost that falls to a few hundred dollars within fifteen years, one of the steepest technological price collapses ever recorded. The decade's worst decision and its best investment, both finished in the same season.

A networked computer with a camera in everyone's pocket, and within a decade the majority of humanity is carrying one — which turns the internet of slot 5 from a place you visited into a layer over everything you do. Facebook and Twitter scale on the back of it, and the business model that pays for all of it is attention sold to advertisers, which makes engagement the thing the systems are optimised for. Every subsequent hour on this face — the Arab Spring, the populist turn, the pandemic's information war — runs through this device, which is why it sits here rather than in a list of gadgets.

American mortgage lending, repackaged into securities nobody could price and spread through a banking system with too little capital, freezes global credit and produces the deepest downturn since era 10's sixth hour. It discredits the market-liberal settlement of era 11's eleventh hour as thoroughly as 1929 discredited the one before, and the response — banks rescued, austerity for everyone else — creates the specific grievance that slot 12 runs on. China's stimulus makes it the world's growth engine and confirms Beijing's read that the western model had been oversold.

A Tunisian street vendor's self-immolation sets off risings across the Arab world, coordinated on the networks of slots 5 and 9, and within months four governments have fallen. Then almost all of it reverses: Egypt returns to military rule, Libya, Syria and Yemen collapse into wars that produce the largest refugee movement since era 10's twelfth hour, and only Tunisia holds — briefly. It is the decisive test of the belief attached to slot 5, and the finding is that a network is very good at removing a government and no help at all in building one, while authoritarian states learn within a few years to use the same tools better than their opponents.

The grievance from slot 10 becomes electoral: Brexit and Trump in 2016, and nationalist parties across the democracies running against migration, expertise and integration itself — the ratchet of slot 3 turning out to be reversible after all. Then in 2020 a coronavirus uses the network exactly as plague used era 05's trade roads, and every state closes the borders that thirty years of policy had been opening, while vaccines are designed in days and delivered in months. The era ends on the same note as era 10's twelfth hour: the problems that matter — pandemic, climate, capital flight, information — are all structurally beyond any single sovereign state, and the sovereign state of era 07's fifth hour is still the only instrument anyone has.

Bronze and Iron. Three thousand years, from the first cities to Persia. Irrigation makes a food surplus, the surplus feeds people who do not farm, and everything follows — writing, kings, priesthoods, law, empire. For most of it the tools of power are scarce and expensive: bronze needs long-distance tin, and scribal scripts need years of training, so both are monopolies. Then the Bronze Age Collapse clears the board, and iron and the alphabet make both cheap. Ends with Cyrus assembling the first multi-ethnic empire out of the much larger pool of armed, literate people that produced.

The Classical Springs. Three hundred years in which four separate traditions — Greek, Chinese, Indian and Roman — work out what a state is for and write the answer down. Small competing states plus cheap iron and cheap literacy produce an explosion of argument: democracy and the republic, the Hundred Schools, Socrates through Aristotle, the Arthashastra. Ends as three of the four are conquered into empires — Alexander's, Ashoka's and Qin's — by the biggest army in their neighbourhood.

Empires of the Old World. The arguing stops and the empires start. Rome in the west and Han in the east each absorb everything within reach, linked by the Silk Road, and both discover the same two things: a road system that moves armies also moves ideas and germs, and an empire that has run out of frontier needs something other than conquest to hold itself together. Christianity is made portable in the middle of it. Ends when plague travels the trade road and both empires crack within a generation of each other.

The Age of Faith. Nine hundred years in which religion, not the state, is the thing that crosses regions. The empires of era 03 fragment, and what replaces them is not a smaller empire but a different kind of institution — one that survives a state's collapse and then supplies what the state used to: law, learning, literacy, legitimacy, and enough shared trust for strangers to trade. Christianity, then Islam, then a Latin church that is the only pan-western institution left standing. Ends as that authority fractures into rival claimants, all of them religious.

Connected Eurasia. Eurasia knits together — Crusades, the Mongol conquests opening a single trade corridor from Korea to Hungary, Italian maritime republics, universities. Then the connection turns lethal: plague travels the same roads, and the Black Death kills perhaps a third of Europe. Ends with plague and Mongol collapse together, and with the Ming closing the road at the far end.

Oceans and Print. Two technologies change the scale of everything — ocean-going ships and movable type. Portuguese and Spanish expansion, the Columbian Exchange and the collapse of the American population, Ming treasure voyages and their abandonment, the Reformation carried by printed pamphlets, the Ottoman and Mughal peaks. The organising condition is that ideas and disease now cross oceans faster than authority can regulate them.

Sovereigns and Science. The state hardens into the sovereign form — Westphalia, standing armies, taxation bureaucracies, public debt — while the scientific revolution establishes a method that does not defer to authority. The two are connected: the same century that decides truth is settled by evidence decides that borders are settled by treaty, and both are answers to a hundred years of killing over who gets to say. Chartered companies and Atlantic slavery pay for all of it.

Revolutions. Industrial, political and colonial revolutions inside a single century, each feeding the others: war debt triggers political revolution, revolution spreads the idea of the sovereign nation, and industry supplies the means — and is then turned outward, on China at the era's eleventh hour. Britain, America, France, Haiti, Latin America. Ends with 1848 — the wave that fails everywhere and thereby sets the terms for the next era.

Empire and Nation. The two forces left over from 1848 — nationalism and industry — stop opposing the state and get absorbed by it. States deliver from above what the barricades demanded from below, and in exchange get conscript armies and taxable industry. Pointed outward, that combination produces the largest land grab in history. German and Italian unification, the scramble for Africa, Meiji Japan, the second industrial wave. Ends when the alliance system built to manage the rivalry executes itself in 1914.

The Thirty-One Years Crisis. Best read as one crisis with an interval, not two wars. Industrial capacity applied to killing, empires collapsing into revolution, an economic depression that discredits the liberal order, and ideologies built to replace it. Ends in 1945 with two superpowers, a ruined Europe, and nuclear weapons.

The Divided World. Two superpowers divide what is left, and find almost immediately that they cannot fight each other — so the contest runs through clients, coups, aid and rockets under a nuclear ceiling neither will break. Underneath it, the thing that moves the most people: the European empires are dismantled in twenty-five years and two thirds of humanity becomes independent, then is asked to pick a side and largely declines. Ends when one superpower decides not to send the tanks.

The Networked World. The bipolar order ends and what replaces it is not a single power but a single network — capital, goods, people, disease and information moving faster than any state can regulate. The era's first half believes the network makes everyone converge on one model; its second half, from the financial crisis onward, is the discovery that it does not. Closes at 2020 by deliberate choice, because the condition has not visibly broken and an era boundary is a claim you cannot honestly make from inside.

Conquest paid for itself in loot and slaves; defence did not. Once the frontier settled roughly on the Rhine, Danube and Euphrates, the army became a permanent cost with no income attached, so the empire had to fund it out of taxation instead of plunder.

Emperors met the shortfall by raising taxes and debasing the silver coinage. Debasement drove inflation, inflation drove tax collection in kind rather than coin, and collection in kind tied producers to their land and trade to local exchange.

Because the army was the only institution that could pay itself, and legions learned they could install an emperor who would reward them. Legitimacy moved from the Senate to whichever field army acted first, so the throne changed hands roughly every two years through the Crisis of the Third Century.

One man could not hold frontiers on the Rhine, Danube and Persian border at once, and every absent emperor invited a usurper. Splitting command put an emperor near each threat. It solved the military problem and created a permanent institutional seam between east and west.

The east held the richer tax base — Egypt, Syria, Anatolia — and a shorter, more defensible land frontier behind Constantinople's walls. The west had longer borders, thinner revenue, and had to buy off or settle the peoples crossing them.

Short of money and manpower, the west settled Goths, Vandals and Franks as federates — allied peoples given land and pay in return for military service. Each settlement transferred tax revenue and armed force to a group that kept its own leaders, so the state progressively subcontracted itself out of existence.

Odoacer deposed Romulus Augustulus and simply stopped appointing a western emperor, sending the imperial regalia east. Roman law, Latin, taxation and the Senate carried on under Germanic kings. Contemporaries did not experience it as an ending — the institutions decayed over generations, not in a year.

It was the one imperial-era institution with literacy, a diocesan structure mapped onto Roman provinces, and property that survived the tax system's collapse. As secular administration failed, bishops absorbed record-keeping, law, charity and negotiation with incoming kings.

With long-distance trade thinned and coinage unreliable, rulers could not pay soldiers in cash. They paid in land instead, granting estates in return for service. Power therefore attached to whoever physically held ground and the people working it.

Expansion stops, so defence must be taxed for; taxation debases the currency and localises the economy; the army becomes the kingmaker; the empire splits to hold its frontiers; the poorer west subcontracts defence to federates; imperial administration decays while the Church survives; without coin, service is paid in land; land-for-service, held personally rather than by the state, is feudalism.