Unit 12 · Faiths, Empires and Exchange

In the year 330 the Roman emperor Constantine chose a new capital. He picked an old Greek town on a narrow strip of water where Europe almost touches Asia. He renamed it after himself: Constantinople. The place was easy to defend and hard to starve. Water surrounded it on three sides, and thick walls closed the fourth. Ships from the Black Sea and the Mediterranean had to pass right beside it, and each one paid a tax.

In 476 the last Roman emperor in the West lost his throne, and the western empire broke into small kingdoms. The eastern half did not break. Its people still called themselves Romans, but historians call their state the Byzantine Empire, after Byzantium, the old name of the city. It lasted from 330 until 1453, more than eleven hundred years. Its people spoke Greek, kept Roman law and followed Christianity.

Constantinople was the largest city in Europe for most of that time, with perhaps several hundred thousand people. Its markets sold silk from China, furs from Russia, spices from India and grain from Egypt. Its gold coin, the solidus, was so trusted that merchants used it from Britain to India. A traveler in the year 1000 who wanted to see the richest city in the Christian world went to Constantinople, not Rome or Paris.

How do we know? The walls still stand in the city now called Istanbul, in Turkey. Byzantine writers left histories, law books and church records. Coins turn up in graves as far away as Sweden. And the city’s enemies wrote about it too, from Arab armies who failed to take it to Vikings who came to serve as the emperor’s guards.

Justinian became emperor in 527. He was born a peasant’s son in the Balkans and rose through his uncle, who was a soldier and then emperor. Justinian wanted to make the empire great again. He sent armies to take back Italy and North Africa. He built churches and fortresses. But his most lasting project was quieter. He ordered a team of lawyers to fix the law.

The problem was a mess. Rome had made laws for a thousand years. Some contradicted others. Some were lost, and some lay buried in thousands of pages of old court opinions. A judge could not know which rule applied. Justinian’s lawyers, led by a scholar named Tribonian, read through it all. Between 529 and 534 they produced a set of books that we call the Code of Justinian, or the Body of Civil Law.

The Code did three things. It threw out laws that no longer made sense. It sorted the rest by topic, so a judge could find the rule on, say, selling a house. And it added a short textbook for law students that began with a definition of justice: giving each person what is due to them. The books were written in Latin, the old language of Rome, even though most people in the empire now spoke Greek.

Centuries later, scholars in Italy rediscovered the Code and taught it in the first universities. Its ideas spread through France, Spain, Germany and their colonies. Today the legal systems of most of Europe and Latin America, and of the state of Louisiana, still trace back to Justinian’s books. A person reading a contract in Mexico City or Paris is using rules a Byzantine emperor had written down.

In January 532 a riot nearly ended Justinian’s reign. Crowds in Constantinople burned half the city, including the main church. The emperor packed to flee. His wife, the empress Theodora, told him she would rather die as a ruler than run. Justinian stayed, his soldiers crushed the riot, and he decided to rebuild the church bigger than anything on earth.

The new church was Hagia Sophia, which means Holy Wisdom in Greek. Two mathematicians designed it. Ten thousand workers finished it in under six years, in 537. Its great dome spans more than a hundred feet and rises about 180 feet above the floor. Forty windows circle the base of the dome, so sunlight pours in and the dome appears to hang in the air. Gold mosaics, tiny glass tiles, covered the walls. A writer of the time said visitors felt the building was not made by human hands.

Hagia Sophia was the center of the Eastern Orthodox Church, the Christianity of the Greek-speaking world. Its leader was the patriarch of Constantinople. Far to the west, the pope in Rome led the Latin-speaking church. The two churches prayed in different languages, argued about the wording of beliefs and about who was in charge. In 1054 their leaders formally split. That break is called the schism, and the Orthodox and Catholic churches remain separate to this day.

The Byzantines sent missionaries north. Two brothers, Cyril and Methodius, made an alphabet for the Slavic peoples in the 800s. Russia, Serbia, Bulgaria and Greece became Orthodox and still are. In 1453 the Ottoman Turks captured Constantinople and turned Hagia Sophia into a mosque. Today the building still stands, and Orthodox churches in Chicago neighborhoods still use domes and icons that look back to it.

Arabia in the year 600 was mostly desert. Its people lived in tribes, raising camels and sheep or trading along the caravan roads. Mecca was a trading town near the Red Sea coast. It also held a shrine, the Kaaba, that drew pilgrims from all over Arabia. They came to honor many gods and to buy and sell. Feuds between tribes were common, and a person without a strong family had little protection.

Muhammad was born in Mecca around 570. His parents died when he was young, and an uncle raised him. He became a merchant, known as honest. Around 610, when he was about forty, he began to report visions in which an angel gave him messages from God. He taught that there is only one God, the same God worshiped by Jews and Christians, and that people should care for the poor, the orphan and the widow. His followers memorized his messages, which were later gathered into the Quran, the holy book of Islam.

The leaders of Mecca did not like this teaching. It insulted their gods and threatened their pilgrim trade. They harassed Muhammad’s followers. In 622 he and his followers left for the town of Yathrib, later called Medina. This journey is the hijra, and Muslims count their calendar from that year. In Medina, Muhammad became a leader of the community and settled disputes among its tribes.

By the time Muhammad died in 632, most of Arabia had accepted Islam. The word Islam means submission to God, and a Muslim is one who submits. The faith asked five main duties of every believer: to declare that there is one God and Muhammad is his messenger, to pray five times a day, to give to the poor, to fast during the month of Ramadan, and, if able, to make the pilgrimage to Mecca once in life. Every duty was the same for a rich man and a poor one.

When Muhammad died, his followers chose a leader called a caliph, meaning successor. The first four caliphs ruled from Medina. Their armies moved fast. The Byzantine and Persian empires had worn each other out in long wars, and their people were heavily taxed. Arab armies took Syria, Egypt and Persia within twenty years. Many local people did not fight hard for the old rulers.

A family called the Umayyads took the caliphate in 661 and moved the capital to Damascus in Syria. Under them the empire reached Spain in the west and the Indus River in the east by about 750. Then a rival family, the Abbasids, overthrew them. The Abbasids built a new capital in 762 on the Tigris River: Baghdad. Within a century it was one of the largest cities in the world, a round city of palaces, markets and canals.

Ruling so many peoples took more than swords. Christians and Jews were called People of the Book, because they too had scriptures. They could keep their religion and their churches if they paid a special tax. Many did, and for centuries most people in Egypt and Syria remained Christian. Over time many converted, partly because Muslims paid less tax and could rise in government.

The empire was never fully united. Spain broke away under its own Umayyad ruler. Later, other rulers in Egypt and North Africa claimed the title too. Even so, from Cordoba in Spain to Samarkand in Central Asia, people shared Arabic as the language of learning and law, the same coins, and the same duty to travel to Mecca. That shared world is what let a king from Mali cross it in 1324.

In the early 800s the caliph al-Ma’mun paid scholars in Baghdad to collect books. Greek, Persian and Indian works were translated into Arabic. Historians call this effort the House of Wisdom. It was part library, part translation office, part research center. Christian, Jewish and Muslim scholars worked there together. Paper, a Chinese invention, had recently reached the Muslim world, and it made books far cheaper than parchment.

One scholar, Muhammad al-Khwarizmi, wrote a book around 820 on solving problems with unknown numbers. Its title used the Arabic word al-jabr, and from that we get the word algebra. He also explained the number system from India, which used ten symbols and a zero. We still call them Arabic numerals because Europe learned them from Arabic books. The word algorithm, a set of steps for solving a problem, comes from his name.

Astronomers built observatories and measured the positions of stars more carefully than the Greeks had. They improved the astrolabe, a brass instrument that finds the time and one’s position from the stars. Muslims needed it to know the hour of prayer and the direction of Mecca, and sailors needed it at sea. Many star names we still use, like Aldebaran and Rigel, are Arabic.

A Persian physician, Ibn Sina, known in Europe as Avicenna, wrote a huge medical textbook around 1025. Doctors in Europe used it for five hundred years. Hospitals in Baghdad and Cairo treated patients of any religion. When European scholars in the 1100s wanted Aristotle, Euclid or the latest medicine, they went to Spain to translate it from Arabic. Much of ancient Greek science survived because Baghdad had saved it.

The Sahara is the largest hot desert on earth, about the size of the United States. Crossing it from north to south meant weeks of sand, rock and heat with water only at scattered oases. Horses and donkeys died. Then, around the 300s CE, herders in North Africa began using the camel, brought from Arabia. A camel can carry several hundred pounds and go a week or more without drinking. It can close its nostrils against sand. Traders called it the ship of the desert.

A trading trip was a caravan: dozens or hundreds of camels, guides who knew the wells, and armed guards. The main route ran from Sijilmasa in Morocco south to the Niger River, roughly a thousand miles, taking about two months. Caravans traveled by night in the hottest season and steered by the stars. A lost caravan was a dead one, and the desert is scattered with old bones to prove it.

The trade worked because each side had what the other lacked. In the middle of the desert, at a place called Taghaza, workers cut slabs of salt from the ground like stone. The lands south of the desert had almost no salt, and people and animals cannot live without it. South of the desert, in the forests along rivers, people dug gold from the earth. North Africa and Europe wanted that gold for coins. Salt went south, gold went north.

Traders also carried copper, cloth, horses and books south, and brought ivory, kola nuts and enslaved people north. Along with the goods came Islam. Merchants from North Africa were Muslims, and they settled in the trading towns south of the desert. Over centuries, kings and city people there adopted the faith, learned Arabic and built mosques. Village farmers often kept older beliefs much longer.

The first great kingdom on the southern edge of the Sahara was Ghana. It lay in what is now Mali and Mauritania, far northwest of the modern country named Ghana, which took the old name in 1957. Ghana’s people, the Soninke, controlled the strip of land between the salt mines to the north and the gold fields to the south. Every trader had to pass through, and every load paid a tax coming in and going out.

Almost everything we know about Ghana comes from writers in the Muslim world who never saw it. The best is al-Bakri, a scholar in Spain, who in 1068 wrote down what traders told him. He described the capital as two towns six miles apart: one for Muslim merchants with a dozen mosques, and one for the king, with his palace and his own religion’s shrines. The king sat in a pavilion with gold-decked horses and dogs in gold collars. Al-Bakri said the king could put a huge army into the field.

The king kept control of gold with a clever rule. All nuggets found in the kingdom belonged to him. People could keep only gold dust. This kept nuggets from flooding the market and made gold stay valuable. Al-Bakri also reported that a load of salt paid one gold coin entering and two leaving. This is a tax on trade, and it is the source of Ghana’s wealth.

Ghana had no written records of its own that survive, so historians are careful. Al-Bakri’s numbers came from travelers and may be stretched. But archaeologists have dug a large stone town at a site called Koumbi Saleh in Mauritania that matches his description of the merchant town. By the 1200s Ghana had weakened, hurt by attacks from the north and by new gold fields opening farther south, outside its control.

Around 1235 a leader named Sundiata united the Mande people and defeated a rival king in battle. He founded the Empire of Mali, which grew to include the old lands of Ghana and the new gold fields to the south. Storytellers called griots have passed down Sundiata’s story by memory for nearly eight hundred years. It is one of the great epics of Africa, and it is also a source historians use, carefully, alongside written records.

Mali’s most famous ruler, Mansa Musa, took the throne around 1312. Mansa means ruler or king. His pilgrimage to Mecca in 1324 was the event you read about at the start of this chapter. On his way home he brought back scholars, architects and books. He had mosques built in Timbuktu and Gao. Fifty years later a mapmaker in Spain drew the Catalan Atlas and showed Mansa Musa sitting on a throne in the middle of Africa, holding a gold nugget. Europe now knew where the gold came from.

Timbuktu sat where the Niger River came closest to the desert. Salt caravans from the north and boats of grain and gold from the south met there. By the 1400s it had a university based at the Sankore mosque, and scholars wrote and copied books on law, religion, math and astronomy. Families in Timbuktu still keep thousands of these old manuscripts today. They prove that West Africa had a written learned tradition long before Europeans arrived.

The traveler Ibn Battuta visited Mali in 1352 and 1353. He praised the safety of its roads and the fairness of its judges. He also complained about customs he found strange and about the small gifts he received. His account is valuable because he was an outsider who saw things the empire’s own people would not bother to write down. By the 1400s Mali weakened, and the empire of Songhai took over Timbuktu.

On a high plateau in southern Africa stand the stone walls of Great Zimbabwe. The word zimbabwe means houses of stone in the Shona language. The largest structure, the Great Enclosure, has curved walls up to about 36 feet high and as much as 16 feet thick, built from cut granite blocks laid without mortar. Inside stands a solid stone tower shaped like a cone. Between about 1100 and 1450, this was the capital of a kingdom of the Shona people.

The rulers of Great Zimbabwe raised cattle and controlled gold mines on the plateau. Gold went east, to the coast, and goods came back. Archaeologists digging inside the walls have found glass beads from India, pieces of Persian pottery and Chinese porcelain. A coin from the Swahili city of Kilwa turned up there too. A city with no writing left records anyway: the things it bought tell us who it traded with.

Historians estimate that ten thousand or more people lived in and around the walls at the city’s height. The walls do not look like a fort. There are no towers for archers. Instead they seem built to show power, to separate the ruler’s family from everyone else. Soapstone carvings of birds, found on the site, are now the symbol of the modern nation of Zimbabwe. Sometime in the 1400s the city was abandoned, perhaps because grazing land and firewood ran out.

For a long time, white settlers and colonial officials refused to believe Africans had built it. They claimed it was the work of ancient Phoenicians or a lost white race. Archaeologists who dug there in the early 1900s, including a British scholar named Gertrude Caton-Thompson in 1929, showed clearly that the builders were local Africans. The government of the colony then called Rhodesia still tried to suppress that finding for decades. The stones did not lie, but some people did.

The Indian Ocean has a gift for sailors: the monsoon winds. For half the year they blow from Africa toward India, and for the other half they blow back. A ship could ride one wind out and the other home. Sailors from Arabia, Persia and India had used these winds for centuries. By the 800s they were trading regularly with towns along the coast of East Africa, in what are now Somalia, Kenya, Tanzania and Mozambique.

Those towns became city-states, each with its own ruler. Mogadishu, Mombasa, Zanzibar and Kilwa were the best known. The people were African, mainly Bantu-speaking, but merchants from Arabia and Persia settled among them, married local women and brought Islam. The mix produced the Swahili language and culture. Swahili is a Bantu language with many Arabic words, and it is still spoken by tens of millions of people in East Africa today.

Kilwa, an island off Tanzania, controlled the gold coming from the Zimbabwe plateau. Its rulers built a palace of coral stone with a swimming pool, and a great mosque with domes. Kilwa minted its own copper coins. Ibn Battuta stopped there in 1331 and called it one of the most beautiful and well-built towns he had seen. Its merchants sold gold, ivory and enslaved people, and bought cloth, porcelain and glass.

In the early 1400s the Chinese admiral Zheng He sailed fleets of huge ships across the Indian Ocean and reached the Swahili coast. A ruler there sent a giraffe back to the Chinese emperor as a gift. Then in 1498 Portuguese ships rounded the southern tip of Africa and arrived at the coast. Within a few years they had bombarded Kilwa and Mombasa. The old trading world of the Indian Ocean would never be the same.

Put the pieces of this chapter on one map. A camel caravan carries gold north from Mali to Morocco. A ship carries it to Cairo, where it is struck into coins. Byzantine merchants and Italian traders carry those coins to Constantinople and Venice. Meanwhile, gold from Zimbabwe goes east through Kilwa, across the ocean to India, and on to China. Paper from China reaches Baghdad, then Cairo, then Timbuktu. No single trader went all the way. But the routes connected, link by link.

Ideas moved along with goods. Islam traveled with merchants to West Africa and the Swahili coast. Greek science, saved in Arabic in Baghdad, reached Spain and then European universities. The numerals from India reached Europe through Arabic books. A student in Timbuktu and a student in Cordoba might study the same law book. A doctor in Paris in the 1300s read a Persian textbook. Religion, math and medicine crossed deserts and oceans.

The same routes carried people who had no choice. The trans-Saharan trade and the Indian Ocean trade both moved enslaved Africans north and east, to Egypt, Arabia, Persia and India, over many centuries. Al-Bakri, Ibn Battuta and Kilwa’s merchants all mention it plainly. Later, from the 1500s on, European ships would carry a far larger number of enslaved Africans west across the Atlantic. The history of trade is also a history of who paid its price.

By about 1450 this connected world was ready for something new. Sailors on the Swahili coast and the Atlantic coast of Morocco knew the winds. Maps in Spain showed where Mali’s gold lay. The Ottoman Turks were about to take Constantinople and its trade routes. Portuguese captains were pushing down the coast of Africa. The next chapter turns to Europe, the Mongols and the Americas, and the world that was about to collide.

After the western Roman Empire broke up in the 400s, there was no emperor to build roads, pay soldiers or keep order. Vikings raided from the north, Magyars from the east, and Muslim fleets from the south. Kings were weak and far away. People needed protection close by. Out of that need grew a system historians call feudalism.

It worked like a ladder of promises. A king granted a large piece of land to a powerful noble, a lord. In return the lord swore loyalty and promised to bring soldiers when the king called. The lord then granted smaller pieces to knights, armored fighters on horseback, who swore the same to him. The land a knight or noble held was his fief. Everyone on the ladder owed something to someone above.

At the bottom were the farmers. Most were serfs. A serf was not a slave and could not be sold, but he could not leave the lord’s land, and his children were serfs too. He farmed strips in the lord’s fields, gave the lord part of his crop and worked the lord’s own land several days a week. In return the lord let him farm and promised to protect him. The lord’s house, the church and the farmers’ huts together made up a manor, and most manors produced nearly everything they needed.

How do we know? The Domesday Book, a survey that King William of England ordered in 1086, lists thousands of manors, their lords, their plows, their mills and their serfs by number. Court records show serfs fined for missing work or for marrying without permission. Castles, at first wooden towers on earth mounds and later great stone fortresses, still dot the land where lords once ruled. Feudal Europe left a lot of paper and a lot of stone.

In feudal Europe, kingdoms came and went, but one thing was the same in every village: the Church. Nearly everyone in western Europe was a Catholic Christian. The parish priest baptized babies, married couples and buried the dead. The Church ran the only schools and hospitals. It collected a tax of one tenth of everyone’s income, the tithe. Monasteries, communities of monks, copied books by hand and kept farming skills and Latin learning alive when few others could read.

At the top stood the pope in Rome, whom Catholics saw as the head of the Church on earth. Popes crowned emperors and sometimes fought with kings over who could appoint bishops. A pope’s strongest weapon was excommunication, cutting a person off from the Church and its sacraments. For a believer, that meant fear for his soul. In 1077 a German emperor stood barefoot in the snow for three days to beg a pope’s forgiveness.

In the 1100s and 1200s, towns competed to build the grandest church. A cathedral was the church of a bishop, and the new style, later called Gothic, used pointed arches and outside supports called flying buttresses to raise walls higher than ever. That let builders fill the walls with huge windows of colored glass. The cathedral at Chartres in France, finished in the 1220s, still has most of its original glass, telling Bible stories to people who could not read.

A cathedral took generations. Masons, carpenters and glassmakers worked their whole lives on one building and died before it was done. The money came from the tithe, from gifts of nobles, and from pilgrims who paid to see holy relics. Some people grumbled about the cost while they went hungry. But when a farmer walked into a cathedral, he stood in the largest indoor space he would ever see, filled with colored light. That was the point.

Jerusalem is holy to Jews, Christians and Muslims. Muslim rulers had held it since 638, and for centuries Christian pilgrims visited without much trouble. In the 1000s a new group, the Seljuk Turks, took over the region and defeated the Byzantine army. The Byzantine emperor asked the pope for help. In 1095 Pope Urban II gave a speech in France calling on knights to march east, free the holy city and win forgiveness for their sins. The crowd shouted that God willed it.

Tens of thousands went. The armies of the First Crusade captured Jerusalem in 1099 and massacred many of its Muslim and Jewish people. The crusaders set up small kingdoms along the coast. In 1187 the Muslim leader Saladin retook Jerusalem. He spared most of the city’s people, and even his enemies wrote of his fairness. More crusades followed for a century, but none won Jerusalem back for long. In 1204 one crusader army never reached the Holy Land at all; it attacked and looted Constantinople, a Christian city, instead.

The crusaders also attacked at home. On their way east in 1096, some bands murdered Jews in cities along the Rhine River. That pattern of violence against Jewish communities returned during the plague and for centuries after. Muslims, Jews and Byzantine Christians all wrote accounts of the crusades, and their view was very different from the knights’ songs. Historians read all of them.

The crusades failed at their goal, but they had effects no one planned. Italian cities like Venice and Genoa grew rich shipping soldiers and supplies and bringing back spices, silk and sugar. Europeans tasted goods from the East and wanted more. Scholars in contact with the Muslim world brought back Arabic books on math, medicine and Greek philosophy. Kings who taxed for the wars grew stronger, and many nobles who went east never came home.

The plague began in Central Asia and traveled the trade routes the Mongols had opened. In 1347 ships from the Black Sea brought it to Sicily. By 1348 it was in Italy, France, Spain and England. By 1351 it had reached Russia and Scandinavia. Trade had connected the world, and the connection carried death as well as silk.

The disease is caused by a bacterium carried by fleas that live on rats. Fleas jumped from dying rats to people. A second form spread directly from person to person by coughing. No one in 1348 knew any of this. Scientists confirmed the bacterium in the 1890s, and in the 2000s they found its DNA in the teeth of plague victims dug from medieval cemeteries. That is how we know the killer’s name today.

The count is rough, because medieval records are patchy, but historians estimate that between a third and half of Europe’s people died within about four years. Some villages lost everyone. In Florence, the writer Giovanni Boccaccio described dead bodies piled in the streets and neighbors who abandoned each other. Records of English manors show fields left empty and rents unpaid. Some people turned to extreme religion, whipping themselves in the streets. Others blamed Jewish communities and killed thousands in Germany and elsewhere.

Then came a surprise. With so few workers left, a serf who survived could demand wages, or walk to a lord who would pay them. In 1351 the English parliament passed a law ordering pay frozen at the old rates. It did not work. When the government tried to raise taxes in 1381, English peasants rose in revolt and marched into London. The revolt was crushed, but serfdom kept fading. A century after the plague, most English farmers were free tenants paying rent, not serfs owing labor.

King John of England was losing. He had lost his lands in France in war, and to pay for more war he squeezed his barons, the great lords, for money. He seized land, demanded huge fees when a noble inherited, and jailed men without trial. He also quarreled with the pope, who cut England off from church services for years. By 1215 the barons had had enough. They raised an army and took London.

In June 1215, in a meadow beside the Thames River called Runnymede, John met the barons and put his seal on a long document in Latin. We call it Magna Carta, the Great Charter. Most of its sixty-some clauses were about the barons’ own complaints: inheritance fees, forests, fish traps in the river. But a few clauses said something bigger. The king could not take new taxes without the consent of his great council. And no free man could be jailed, stripped of property or exiled except by the judgment of his peers or the law of the land.

John never meant to keep it. Within months the pope declared the charter void and war began again. But John died in 1216, and his young son’s advisers reissued the charter to win support. Kings confirmed it again and again over the next century. Each time, the idea sank deeper: the king rules under the law, not above it. The great council grew into Parliament, which held the power over taxes.

Five hundred years later, English colonists in America knew Magna Carta well. When they said no taxation without representation, they were pointing to it. When the United States Constitution promised that no one could lose life, liberty or property without due process of law, it echoed the clause sealed at Runnymede. A copy of the 1215 charter is displayed in the National Archives in Washington, next to the Declaration of Independence.

North of China stretches the steppe, a sea of grass too dry for farming. Its people lived by herding horses, sheep and cattle, moving with the seasons and living in round felt tents. Boys learned to ride and shoot a bow before they could plow. The tribes fought each other constantly. Around 1162 a boy named Temujin was born there. His father was poisoned by enemies when Temujin was about nine, and his family was left to starve on the steppe.

Temujin survived by building alliances, and by 1206 he had united all the Mongol tribes. They gave him the title Genghis Khan, universal ruler. He organized his army in groups of ten, a hundred, a thousand and ten thousand, mixing the tribes so that loyalty went to him, not to old clans. He promoted men for skill, not birth. His riders could travel fifty miles or more a day, each with several spare horses, and shoot accurately from the saddle at a gallop.

Then he turned outward. Cities that surrendered were spared and taxed. Cities that resisted were destroyed as a warning, and Mongol armies killed on a scale that horrified every writer of the age. By his death in 1227 Genghis ruled from northern China to the Caspian Sea. His sons and grandsons pushed on into Russia, Persia and eastern Europe. In 1258 they took Baghdad, killed the caliph and ended the Abbasid caliphate. In 1279 his grandson Kublai Khan finished conquering China and ruled it as emperor.

At its height the Mongol Empire stretched from Korea to Hungary, the largest connected land empire ever. It was really four related empires ruled by Genghis’s descendants. Historians debate how to weigh the destruction against what came after. Persian and Chinese writers recorded the massacres in detail. But the same writers, a generation later, worked for Mongol rulers who paid for observatories, histories and hospitals.

Once the conquests slowed, the Mongols wanted the wealth that trade brought. They set up relay stations about a day’s ride apart across Asia, with fresh horses and food for official messengers. A message could cross the empire in weeks. Merchants with a Mongol pass could travel under protection. Historians call this period, roughly 1250 to 1350, the Pax Mongolica, the Mongol Peace. A saying of the time claimed a girl with a bag of gold could walk across the empire unharmed.

In 1271 a seventeen-year-old from Venice named Marco Polo set out with his father and uncle, who were merchants. They crossed deserts and mountains for more than three years to reach the court of Kublai Khan in China. Marco stayed about seventeen years, working for the khan and traveling across China. He came home in 1295. Captured in a war between Venice and Genoa, he dictated his story in prison to a writer of romances.

His book described things Europeans found hard to believe: a city with canals and twelve thousand bridges, coal burned as fuel, paper money printed by the government, and a postal system faster than anything in Europe. Some readers called him a liar. Some historians still argue about which parts he saw himself and which he heard from others. But much of what he wrote checks out against Chinese records, and his book became a favorite of a later sailor named Christopher Columbus.

The Mongol Peace carried more than merchants. Chinese inventions such as gunpowder, printing and the compass moved west along the same roads. So did the plague in the 1340s. And the peace did not last. The Mongol khanates fought each other, China threw out its Mongol rulers in 1368, and the roads grew dangerous again. Europeans who had tasted Asian silk and spices now looked for another way to reach them, by sea.

Japan is a chain of mountainous islands off the coast of Asia. It borrowed writing, Buddhism and government ideas from China and Korea, but it was never conquered by them. For centuries an emperor in the city of Kyoto stood at the top of Japanese society, seen as descended from the sun goddess. But by the 1100s the emperor had little real power. Great families with private armies fought each other for control.

In 1185 a warrior named Minamoto Yoritomo won that war. In 1192 the emperor gave him the title shogun, which means great general. The emperor kept his throne and his ceremonies, but the shogun ran the country from his own headquarters. For nearly seven hundred years, until 1868, shoguns ruled Japan in the emperor’s name. Under the shogun, lords called daimyo held land and kept armies of warriors called samurai.

A samurai was much like a European knight. He fought on horseback with bow and sword, served a lord, and received land or rice in return. He followed a code of loyalty and honor that later got the name bushido, the way of the warrior. A samurai who failed his lord was expected to take his own life. Samurai families also produced poets, painters and Buddhist thinkers, and the tea ceremony grew up in their world.

The shoguns faced their greatest test from the Mongols. Kublai Khan sent fleets to invade Japan in 1274 and again in 1281, with tens of thousands of soldiers. Both times the samurai fought on the beaches, and both times huge storms wrecked the Mongol ships. The Japanese called those storms kamikaze, divine winds. Japan stayed independent, but the shogun could not reward his samurai with new land, because there was none to give, and his rule weakened.

In what is now Guatemala, Belize, southern Mexico and Honduras, the Maya built cities in the jungle. Their greatest period ran from about 250 to 900 CE. Cities such as Tikal and Copan held tens of thousands of people, with stone pyramids taller than any building in Europe at the time, plazas, palaces and ball courts. Each city had its own king. They traded with each other and fought each other, like the city-states of Greece.

The Maya are the only people of the ancient Americas known to have had a full writing system. Their glyphs, picture-like signs, could spell any word in their language. They carved them on stone monuments and wrote them in folding books of bark paper. For a long time no one could read them. Scholars cracked the code mainly in the second half of the 1900s. Now we can read the names of Maya kings and the dates of their battles.

Maya astronomers watched the sky for generations and wrote down what they saw. They tracked the planet Venus so closely that their tables were off by only a day or two in a century. They used a symbol for zero and a place-value number system, centuries before Europe learned one. They kept several calendars at once, including one that counted every day from a starting point more than three thousand years before their time.

Around 900 the great cities of the south were abandoned. Historians still argue why. Evidence points to long droughts, recorded in lake mud and cave stones, along with overuse of the forest, war between cities and kings who lost their people’s trust. But the Maya did not vanish. Cities in the north, like Chichen Itza, thrived for centuries more. Today about six million Maya people live in Central America and speak Maya languages.

According to their own history, the Mexica, whom we call the Aztec, were wanderers who arrived late in the Valley of Mexico. The good land was taken. In 1325 they settled on a swampy island in Lake Texcoco, where, their story said, they saw an eagle on a cactus. That image is on the flag of Mexico today. On that island they built Tenochtitlan, which by 1500 was one of the largest cities in the world, with about two hundred thousand people.

Feeding a city on a lake took engineering. The Aztec built chinampas, raised fields made by piling mud and plants in the shallow water and fencing them with willow trees. Farmers could take several harvests of corn, beans, squash and chilies from a chinampa every year. Stone causeways with bridges linked the island to the shore, and an aqueduct carried fresh water from springs. Canoes moved through canals, and a market in the district of Tlatelolco drew tens of thousands of people a day.

In 1428 the Aztec joined two neighboring cities in an alliance and began conquering the valley and far beyond. Conquered peoples paid tribute: corn, cotton cloth, feathers, cacao beans, gold and captives. Records list every town and exactly what it owed. Aztec religion held that the gods needed human blood to keep the sun moving, and captives from war were sacrificed at the great temple. Neighboring peoples hated Aztec rule, and that hatred mattered later.

Spanish soldiers who saw Tenochtitlan in 1519 wrote that it looked like a dream, with towers rising from the water. Within two years they had destroyed it, with the help of smallpox and tens of thousands of native allies who wanted to end Aztec rule. Mexico City stands on the site today. Archaeologists digging under its streets have found the great temple, and the Aztec tribute lists survive because the Spanish copied them to learn what they could collect.

The Andes Mountains run down the west side of South America, and their peaks stand more than twenty thousand feet high. Farming there means building terraces, flat steps cut into the mountainsides and walled with stone. Andean peoples grew potatoes and corn on them and raised llamas and alpacas for wool and carrying loads. Around 1438 a ruler of a small mountain kingdom at Cusco, in Peru, began conquering his neighbors. His people were the Inca.

In less than a century the Inca ruled from what is now Colombia to Chile, about 2,500 miles along the mountains, with perhaps ten million people. They held it together with roads. Two main highways, one along the coast and one through the mountains, plus side roads, added up to roughly 25,000 miles. Rope bridges swung across gorges. Runners in relays carried messages along the roads at a pace of a hundred miles or more a day. Storehouses along the way held food, cloth and weapons for armies and for villages in bad years.

The Inca had no writing. Instead officials kept records on a quipu, a set of colored strings with knots. The position and type of knot recorded numbers: how many people in a village, how many llamas, how much corn in a storehouse. Every family owed the state labor, called mita, for building roads, terraces and cities. In return the state fed people in famine. Conquered peoples were sometimes moved far from home to break up resistance.

Inca builders cut stones so exactly that they fit without mortar, and the walls of Cusco still stand under Spanish churches built on top of them. Machu Picchu, a royal estate high on a ridge, was never found by the Spanish and survives nearly whole. The Inca did all this without iron tools, wheeled carts or horses. When Spanish soldiers arrived in 1532, a civil war and smallpox had already weakened the empire, and the Inca rulers fell within a few years.

Stand on the world in 1450 and look around. In China the Ming dynasty rules perhaps a hundred million people, the most on earth. Twenty years earlier its emperor sent Zheng He’s giant fleets to India and Africa, then stopped and let the ships rot. In India, Persia and the Ottoman lands, Muslim rulers govern rich cities. Along the Swahili coast and across the Sahara, African traders move gold. In Europe, small kingdoms quarrel, and a German craftsman is perfecting a press that prints with movable type.

Across the Atlantic, the Aztec are expanding in Mexico and the Inca in the Andes. Neither knows the other exists. Neither knows of Europe, and Europe does not know of them. In North America, the great mound city of Cahokia, near what is now St. Louis and Collinsville, Illinois, has already been abandoned for a century. Farming towns line the Mississippi and its branches. No one on either side of the ocean has any idea what is coming.

Compare the societies you have met. All built cities. All had religions that shaped law and daily life. Most had writing; the Inca did not. Europe and Asia had horses, iron, wheels and gunpowder; the Americas did not. Africa, Asia and Europe were linked by routes that carried goods, faiths and, in the 1340s, plague. The Americas were sealed off, so their people had never met the diseases of the other continents. That single fact would decide millions of lives.

Three events within a few years turned the page. In 1453 the Ottoman Turks took Constantinople, ending the Byzantine Empire and pushing Europeans to seek sea routes east. Around 1455 Gutenberg’s press printed a Bible, and cheap books spread faster than ever. In 1492 a Genoese sailor who had read Marco Polo sailed west from Spain, looking for Asia, and reached islands no European knew. The next unit begins there.