On the morning of 29 May 1453, the Ottoman army of Sultan Mehmed II breached the land walls of Constantinople and took the city by storm, ending the Byzantine Empire — the surviving eastern half of the Roman state, governed in an unbroken line from the capital Constantine the Great had dedicated as New Rome on 11 May 330. The last emperor, Constantine XI Palaiologos, died in the fighting near the breach; his body was never identified with certainty. After a siege of roughly seven weeks, an empire that traced its authority to Augustus passed out of existence.
By 1453 that empire was already a husk. The polity Mehmed conquered was not the Mediterranean superstate of Justinian but a rump centered on a single decayed city, surrounded on every side by Ottoman territory and surviving largely on Ottoman sufferance. The decisive wound had been inflicted not by Muslims but by fellow Christians: the Fourth Crusade had sacked Constantinople in 1204, broken the empire into Latin and Greek fragments, and drained the strength it never recovered after the Greeks retook the city in 1261. What fell in 1453 had been dying for two and a half centuries.
The mechanism of the final conquest was a collision between an old technology and a new one. The Theodosian Walls, raised in the fifth century, had repelled assault for a thousand years and were the most formidable land fortification in the medieval world. Against them Mehmed brought the largest gunpowder siege train yet assembled, including a monstrous bronze bombard cast by the Hungarian engineer Orban. The walls that had defined the impregnability of Constantinople were, within weeks, reduced to a problem of arithmetic.
The fall reverberated far beyond the Bosporus. It severed the eastern land routes that had carried Asian goods to Europe through Constantinople, sharpening the search for sea passages that became the Age of Exploration; it scattered Greek scholars and manuscripts westward into a Renaissance hungry for them; and it gave the Ottomans an imperial capital they would rule for nearly five centuries. The conversion of the great church of Hagia Sophia into a mosque, ordered by Mehmed on the day of the conquest, fixed the moment in memory as the end of one age and the start of another.
On 13 August 1521, after a siege of some three months, the island city of Tenochtitlan — capital of the Mexica and seat of the Aztec Empire — fell, and its last ruler, the tlatoani Cuauhtémoc, was captured trying to escape across Lake Texcoco by canoe. The empire that had dominated central Mexico for nearly a century was broken. The popular image of that conquest — a few hundred Spaniards under Hernán Cortés overthrowing a civilization of millions — is a myth that flatters the conquerors. The fall of Tenochtitlan was achieved by an army that was overwhelmingly Indigenous, fighting alongside a small Spanish contingent, against a Mexica population already devastated by an epidemic the invaders had brought.
The Aztec Empire that fell was a Mexica-led order, the dominant partner in a Triple Alliance with Texcoco and Tlacopan formed around 1428, which extracted tribute from much of central Mexico through war and the threat of war. Tenochtitlan, built on an island in the lake and laced with canals and causeways, was one of the largest cities in the world, with a population estimated in the hundreds of thousands — larger than most European capitals of the age. Its empire was wealthy, sophisticated, and militarily formidable. It was also resented: the peoples it had subjugated and from whom it demanded tribute and captives were, in many cases, willing to ally with anyone who might break Mexica power.
The mechanism of the conquest rested on three pillars, none of them Spanish superiority alone. First and most important were the tens of thousands of Indigenous allies — above all the Tlaxcalans, an independent people the Mexica had never conquered, who supplied the bulk of the fighting force, the local knowledge, the food, and the manpower without which the small Spanish company could not have taken the city. Second was smallpox, introduced by the Europeans in 1520, which swept Tenochtitlan and killed an enormous share of its people — including the ruler Cuitláhuac — gutting the defense before the final siege began. Third was the siege itself: Spanish-built brigantines cut the lake, the causeways were taken block by block, and the aqueduct supplying fresh water was severed, so that the city fell as much to thirst, hunger, and disease as to assault.
The fall of Tenochtitlan inaugurated three centuries of Spanish colonial rule over the heart of Mesoamerica and a demographic catastrophe — driven above all by epidemic disease — that reduced the Indigenous population of central Mexico by perhaps nine-tenths over the following century. Moctezuma II, the ruler when the Spanish arrived, died in Mexica captivity to the invaders in 1520; Cuauhtémoc, who led the final defense, was kept prisoner, tortured for gold, and hanged in 1525. The empire was not so much defeated in a battle as dismantled by alliance, disease, and siege.
The Inca Empire — Tawantinsuyu, “the four parts together,” the largest state in the pre-Columbian Americas — was broken in 1533 when a small Spanish expedition under Francisco Pizarro seized its ruler, the Sapa Inca Atahualpa, at Cajamarca on 16 November 1532, extracted an immense ransom in gold and silver, and then executed him. The capital, Cuzco, was occupied a year later, on 15 November 1533. The empire that fell ruled some ten to sixteen million people across roughly two million square kilometres of the Andes, from southern Colombia to central Chile, governed by a road system of some 40,000 kilometres and a bureaucracy without writing.
The conquest was not the feat of a handful of Spaniards overawing a docile people. Two catastrophes had struck the Andean world before Pizarro’s 168 men ever reached the highlands. The first was epidemic disease: smallpox, introduced to the Americas by Europeans, swept south ahead of any European traveller and killed the Sapa Inca Huayna Capac around 1528, together with his designated heir. The second flowed from the first — a ruinous civil war of succession between two of Huayna Capac’s sons, Atahualpa and Huáscar, the “war of the two brothers,” which had torn the empire apart and ended only months before the Spanish arrived.
Pizarro exploited both. He landed in a state still bleeding from civil war, its institutions concentrated in the sacred person of an emperor, and he struck at that person directly. Atahualpa, fresh from victory over his brother and camped at Cajamarca with an army that may have numbered in the tens of thousands, agreed to meet the strangers; in a coordinated ambush the Spanish slaughtered thousands of unarmed retainers and took the Sapa Inca alive. With the emperor a hostage, the machinery of a centralized empire could be turned by the hand that held him.
The other decisive element was Andean, not European. The Inca had built their empire by conquest within living memory, and many of the peoples they ruled — among them the Cañari, the Huanca, the Chachapoya, and the Chanka — resented Cuzco and joined the invaders in their tens of thousands, supplying the manpower without which 168 foreigners could have done nothing. The fall of the Inca Empire was an Andean civil catastrophe that Spain harnessed; it should be understood, and remembered, from the side of the peoples who lived it.
On 13 March 1591, on a plain near Tondibi just north of the city of Gao, the army of the Songhai Empire — the largest state in the history of West Africa — was broken by a small Moroccan expeditionary force that had crossed the Sahara armed with gunpowder weapons. The Songhai, fielding tens of thousands of cavalry and infantry under their ruler Askia Ishaq II, met an invading column of a few thousand men sent by Ahmad al-Mansur, the Saadi sultan of Morocco, and commanded by a renegade soldier named Judar Pasha. The Songhai had the numbers; the Moroccans had arquebuses and cannon. Within roughly two hours the Songhai army was routed, and the great cities of the Niger bend — Gao, Timbuktu, and Djenné — passed out of imperial control.
The empire that fell had risen barely more than a century before. Building on the older trading kingdom centered on Gao, Songhai expanded into an imperial power under Sonni Ali, who took control around 1464 and conquered Timbuktu and Djenné, and reached its height under Askia Muhammad, who reigned from 1493 and welded the western Sudan into a single administered state. At its peak Songhai controlled the middle Niger and the trans-Saharan trade in gold, salt, and other goods across a domain of well over a million square kilometers — a wealthy, literate, Islamic civilization whose scholars made Timbuktu a center of learning.
The mechanism of the fall combined a fatal internal weakness with a decisive technological gap. After the death of the long-reigning Askia Daoud in 1582, Songhai was destabilized by a bitter dynastic struggle that brought Askia Ishaq II to a contested throne and left the empire divided at the moment it most needed unity. Into that opening came al-Mansur’s invasion. The Moroccan sultan, drawn by the legendary wealth of the Sudanese gold trade and equipped with firearms the Songhai lacked, gambled on sending a force across one of the world’s harshest deserts. Most of that force perished or turned back on the crossing, but the survivors carried a weapon that the proud Songhai cavalry could not answer.
The encounter at Tondibi made the gap plain. The Songhai are said to have driven a herd of cattle at the Moroccan lines to break them, but the noise of gunfire turned the stampede back onto their own ranks, and the massed arquebus and cannon fire shattered an army built for an earlier kind of war. The victory destroyed Songhai as an imperial power, but it did not give Morocco a usable empire in its place: the conquerors could neither govern nor hold the vast region across the desert, and the middle Niger fragmented into a patchwork of smaller states. West Africa’s greatest empire ended not in a long decline but in a single afternoon, undone by a civil war at home and a handful of guns from across the Sahara.
On 2 January 1492, Muhammad XII of Granada — known to history as Boabdil — surrendered the city of Granada and the Alhambra to Ferdinand II of Aragon and Isabella I of Castile, the Catholic Monarchs. The Nasrid Emirate of Granada, ruled by its dynasty since around 1238, was the last Muslim state in the Iberian Peninsula; its fall completed the Reconquista, the centuries-long Christian conquest of Iberia, and ended nearly eight hundred years of Muslim political presence that had begun with the invasion of 711. Boabdil handed over the keys and, by the famous account, wept as he left; the symbolic age of Al-Andalus was over.
The conquest was the climax of a ten-year war, fought from 1482 to 1492, in which the combined Castilian and Aragonese crowns ground down a fragmented emirate town by town. Granada’s surrender was negotiated, not stormed: the Treaty of Granada, agreed in November 1491, promised the city’s Muslims their lives, property, laws, mosques, and freedom of worship. Within a decade those guarantees were dismantled. Forced conversions began in 1499 under Cardinal Cisneros; by 1501–1502 Granada’s Muslims faced baptism, exile, or slavery, and the Jews of all Spain had already been expelled by the Alhambra Decree of March 1492. The fall of the state became the prelude to the erasure of its people’s faith.
The emirate fell because it was small, isolated, and divided against itself, confronting a Christian power that had grown larger, richer, and newly unified. The marriage of Ferdinand and Isabella in 1469 had joined Castile and Aragon; Granada, by contrast, was riven by dynastic civil war, with Boabdil, his father, and his uncle fighting one another even as the Christians advanced — a rivalry the Catholic Monarchs exploited with deliberate skill. A state that could not unite against an enemy who could concentrate against it had little chance once the war of attrition began.
Technology and resources decided the rest. The Castilian crown brought a powerful siege artillery train that reduced Granada’s fortified towns far faster than walls had once dictated, and it could outspend and outlast an emirate cut off from any great Muslim power that might relieve it. North African aid never came in strength; Christian Iberia had the men, the guns, and the money, and it applied them methodically. After the fall of Málaga in 1487 and Baza in 1489, the capital stood alone, and its surrender was a matter of time.
The Sasanian Empire — the last pre-Islamic Persian empire, founded by Ardashir I in 224 and ruled from its winter capital at Ctesiphon on the Tigris — was conquered by the Arab Muslim armies of the Rashidun Caliphate between roughly 633 and 651. Its last shah, Yazdegerd III, a grandson of the great king Khosrow II, fled eastward across his own collapsing realm for nearly a decade and was killed near Merv in 651, by tradition murdered by a local miller for the jewellery he carried. With his death the dynasty that had been Rome’s and then Byzantium’s principal rival for four centuries ceased to exist, and Iran began its long passage from Zoroastrian empire to part of the Islamic world.
The empire the Arabs broke was, like Byzantium that same century, already gravely wounded — and the wound was largely self-inflicted. The Sasanian and East Roman empires had fought a final, ruinous war from 602 to 628 in which Khosrow II overran Syria, Palestine, and Egypt before the emperor Heraclius drove deep into Persia and shattered his armies. Both empires emerged exhausted, bankrupt, and depopulated by war and plague. When Khosrow was murdered by his own nobles in 628, the Sasanian state fell into a four-year civil war in which a dozen or more claimants — including two queens, Boran and Azarmidokht — passed across the throne before the nobility agreed on the boy Yazdegerd III in 632.
It was onto this enfeebled, faction-ridden empire, not a Persia at its height, that the Arab armies advanced. The conquest came as a sequence of decisive battles against a state that could no longer absorb a single great defeat. At al-Qadisiyyah, around 636, the Arab commander Sa’d ibn Abi Waqqas destroyed the main Sasanian field army and killed its general Rostam Farrokhzad; Ctesiphon fell soon after; and at Nahavand in 642 — remembered in the Arab tradition as the “Victory of Victories” — the last great Persian army was annihilated. Thereafter the provinces fell one by one as Yazdegerd fled before them.
The consequences were civilizational. Zoroastrianism, the state religion, lost its imperial patronage and dwindled over centuries to a minority faith; Persian elites, language, and administrative genius were absorbed into the new caliphate, which they would in turn reshape; and the lands of Iran, conquered as Arab territory, became over generations a heartland of Islam while retaining a fiercely distinct Persian identity. Few conquests have so thoroughly ended one order and seeded another.