The Rise of Islam & the Golden Age

At the beginning of the seventh century, two exhausted superpowers faced each other across the Fertile Crescent. To the west lay the Byzantine Empire—the surviving eastern half of Rome, Christian and Greek-speaking, ruled from Constantinople. To the east lay the Sasanian Empire of Persia, ancient and proud, its kings worshipping fire in the tradition of Zoroaster. For centuries these two giants had bled each other white in wars over Syria, Armenia, and Iraq. By the 620s they had fought themselves to the edge of ruin, their treasuries drained and their provinces sullen. Neither noticed the desert on their southern flank.

Between and below them stretched the Arabian Peninsula: a vast, largely arid expanse of desert and oasis that the great empires regarded as a backwater fit only for raiders and traders. It had no single ruler. Its people, the Arabs, were organized by tribe and clan, bound by ties of blood, honor, and the fierce code of hospitality that desert survival demanded. Most were polytheists, worshipping a crowd of gods and spirits, though Jewish and Christian communities lived among them, and some Arabs, called hanifs, were said to seek the one God of Abraham on their own.

This was a world of poetry and memory more than ink. The Arabs prized eloquence above almost all things; a great poet could make or break a tribe's honor with a verse. Yet it was also a world of hard edges—of blood feud and tribal vendetta, of female infants sometimes exposed to die, of the strong preying on the weak. Later Muslims would remember the age before Islam as the Jahiliyya, the "time of ignorance."

Into this world, according to the traditional reckoning, a boy was born in Mecca around the year 570—an orphan of the Quraysh who would grow into a merchant so honest that his neighbors called him al-Amin, "the trustworthy." His name was Muhammad.

He came into the world already fatherless. Muhammad ibn Abdullah was born, by tradition, around 570 CE—in a year Arab memory called the "Year of the Elephant," after a failed attack on Mecca by an army said to include a war elephant. His father, Abdullah, had died before his birth; his mother, Amina, died when he was about six. Raised first by his grandfather Abd al-Muttalib and then, after the old man's death, by his uncle Abu Talib, the boy grew up an orphan in a society that measured a man by his lineage and protectors.

He grew into a quiet, thoughtful man of unusual integrity. As a young trader on the caravan routes north to Syria, he earned a reputation for honesty and fair dealing so complete that the Meccans gave him a title: al-Amin, the trustworthy. Around the age of twenty-five he entered the service of a widowed merchant named Khadija, managing her trade. Impressed by his character, she proposed marriage. He accepted, and by every account their union was one of deep devotion. Khadija would become not only his wife but his first and most steadfast supporter.

Muhammad was given, tradition holds, to periods of solitude and reflection. He would withdraw to a cave on Mount Hira, a stony height outside Mecca, to think and to pray away from the noise of the town and its idols. It was there, according to Islamic tradition, in about the year 610, during the month later called Ramadan, that his life—and the course of world history—turned.

In the traditional account, the angel Gabriel (Jibril) appeared to him and commanded: Iqra—"Recite," or "Read." Muhammad, who is described in the tradition as unlettered, protested that he could not. The command came again, and then the first words of what Muslims believe to be God's revelation were given to him.

Muslims believe these were the opening words of the Quran—God's final revelation to humanity, delivered through Muhammad over the following twenty-three years. The word Quran itself means "recitation." Shaken to his core, Muhammad hurried home to Khadija, who wrapped him in a cloak and comforted him, and who—tradition says—became the first to believe that the voice was true. Islam dates its beginning to this moment: the conviction of a man that there is no god but God, and that he had been called to say so.

At first Muhammad shared his message quietly, among family and close friends. Its core was startling in its simplicity and its challenge: there is only one God, all-powerful and merciful; the idols of the Kaaba are nothing; every human being will be judged after death; and the rich and powerful owe justice and charity to the poor, the orphan, and the slave. To a proud, hierarchical, polytheistic society, each of these claims was a provocation.

The earliest believers were a small band: Khadija; the young Ali ibn Abi Talib, the Prophet's cousin; his freedman Zayd; and the respected merchant Abu Bakr, who would become his closest companion. As the circle widened, so did the alarm of the Quraysh. Mecca's leaders drew wealth and status from the pilgrimage to the idols. A preacher who called those idols false, and who taught that a slave was equal before God to a chieftain, threatened both their religion and their revenue.

Persecution followed. Believers of low status—especially slaves and the poor, who had no powerful clan to shield them—were beaten, imprisoned, and tortured. One of them, an Ethiopian slave named Bilal, was pinned under a rock in the desert sun to make him recant; he refused, and would later become Islam's first muezzin, the caller to prayer. To spare the vulnerable, Muhammad sent a group of followers across the Red Sea to Christian Abyssinia (Ethiopia), whose king gave them refuge—the first migration, or hijra, in Islam's history.

Then, within a short span around 619, Muhammad lost his two great protectors: Khadija, his wife, and Abu Talib, the uncle whose clan standing had shielded him. Muslims remember it as the "Year of Sorrow." Exposed and grieving, with the message stalled in a hostile city, Muhammad's position in Mecca had become perilous.

In 622 the believers slipped out of Mecca in small groups, and Muhammad, evading a plot against his life, made the journey north with Abu Bakr. This migration—the Hijra—is one of the pivotal events in world history. It marks the moment Islam became not merely a private faith but a community with a home. So decisive was it that when Muslims later fixed a calendar, they set its first year not at the Prophet's birth, nor at the first revelation, but at the Hijra. The Islamic year is still counted AH—Anno Hegirae, "in the year of the migration."

In Medina, Muhammad became something no prophet in the biblical tradition had quite been in his own lifetime: the head of a community and a state. He arbitrated disputes, made law, led worship, and governed. One of his first acts was to draw up an agreement—later called the Constitution of Medina—binding the town's clans, including its Jewish tribes, into a single community, or umma, with mutual obligations of defense and shared arbitration. It was, in effect, a charter for a plural society under a common peace.

But Mecca had not forgotten. The Quraysh regarded the exiles as rebels and their prophet as a mortal threat, and the two cities slid into war. The conflict turned on the caravan trade that was Mecca's lifeblood, and it produced a handful of battles that Muslim memory holds sacred.

The tide turned slowly toward Medina. In 628 Muhammad led a body of unarmed pilgrims toward Mecca and, rather than fight, negotiated the truce of Hudaybiyya—a pause that many of his followers thought a humiliation but that let the faith spread in peace. Two years later, when the truce collapsed, Muhammad marched on Mecca with a large force. In 630 the city that had driven him out surrendered largely without bloodshed. He entered as its master, and—according to tradition—ordered the idols of the Kaaba destroyed, rededicating the ancient shrine to the worship of the one God. Rather than take revenge on his old persecutors, he proclaimed a general amnesty.

In the two years that followed, most of the Arabian tribes came into the fold, by treaty or conversion. In 632 Muhammad made a final pilgrimage to Mecca—the "Farewell Pilgrimage"—and, according to tradition, delivered a sermon on Mount Arafat that Muslims still cherish, calling for equality, the sanctity of life and property, and the fair treatment of women. Islam holds that the revelation of the Quran was by then complete.

A few months later, in June 632, back in Medina, Muhammad fell ill and died, his head—tradition says—resting in the lap of his wife Aisha. He was about sixty-two. He left no clear instruction about who should lead after him, and no surviving son. He left instead a book his followers believed to be the word of God, a community that ruled most of Arabia, and a faith poised to astonish the world. His companions were stunned; it fell to Abu Bakr, tradition records, to steady them with the reminder that they had followed God, who does not die, and not merely a man.

The Prophet's death left an urgent question: who now leads? He was, Muslims believe, the last of the prophets—no one could replace him in that role. But the community needed a head of state and defender of the faith. The answer was a new office: the khalifa, or caliph, meaning "successor" or "deputy." The first four, chosen from among Muhammad's closest companions, are remembered by most Muslims as the Rashidun—the "Rightly Guided" caliphs—and their thirty years as a kind of golden dawn.

Abu Bakr first had to hold the community together. On the Prophet's death, several Arabian tribes tried to break away; Abu Bakr's short, sharp campaigns—the Ridda or "apostasy" wars—kept Arabia united. Tradition records that he defined the new office with humility, telling the people that he was no better than they, that they should correct him if he did wrong, and that they owed him obedience only so long as he obeyed God and the Prophet. Then, under Abu Bakr and especially his successor Umar, the Arab armies turned outward—and the world tilted.

What followed is among the most astonishing military expansions in history. The two exhausted empires that had ignored Arabia now paid the price. At the Yarmouk (636) the Arabs shattered a Byzantine army and tore Syria from Constantinople; at al-Qadisiyya (636) they broke the Sasanian Persians. Damascus fell, then Jerusalem in 637, then the Persian capital of Ctesiphon; Egypt was taken by 641. Within a single generation, the entire Sasanian Empire had been absorbed and the Byzantines driven back to Anatolia.

How did it happen? Historians point to several causes at once: two imperial rivals bled dry by their own long war; local populations, many of them taxed and persecuted by Constantinople or Ctesiphon, who found the Arab newcomers no worse and often lighter-handed; the mobility of desert armies; and, binding it all, the fervor and unity of a new faith. In the conquered lands, Jews, Christians, and Zoroastrians—the "People of the Book"—were generally allowed to keep their religion in exchange for a tax, the jizya. Conversion, in these early generations, was often slow; the conquerors were a ruling minority atop a vast non-Muslim majority.

The age had its own tragedies. Umar, perhaps the greatest of the four, was assassinated in 644 by a captured Persian craftsman with a personal grievance. His successor Uthman was murdered in 656 by mutineers from the army—the first time Muslims had killed a caliph, and a wound that would not heal. Yet Uthman left one enduring gift: fearing that variant recitations of the Quran might divide the faithful, he ordered a single authoritative text compiled from the memories of those who had learned it from the Prophet and from the written fragments already collected. That standard Quran, tradition holds, is in all essentials the one Muslims recite today.

The deepest division in Islam did not begin as a quarrel about doctrine. It began as a question about leadership—who had the right to lead the community after the Prophet—and it is best understood, by an outside observer, as a political and dynastic dispute that hardened over time into two great traditions. This chapter tells that story plainly and without taking sides, because both traditions are held sincerely by many millions, and each remembers these events as sacred.

From the very first, some Muslims had believed that leadership belonged by right to the Prophet's own family—the Ahl al-Bayt, "the People of the House"—and above all to Ali ibn Abi Talib, Muhammad's cousin, the husband of his daughter Fatima, and among the earliest believers. This party came to be called the Shiat Ali, "the party of Ali," from which comes the word Shia. Others held that leadership should fall to the most capable and respected companion, chosen by the community's consensus, following the practice (sunna) of the Prophet and the example of the first caliphs; they came to be called Sunni. In the first three successions, the choice had gone to Abu Bakr, Umar, and Uthman before Ali.

Ali finally became caliph in 656, in the shadow of Uthman's murder—and inherited a community already at war with itself. His right to rule was challenged, and his caliphate was consumed by civil strife, the first fitna ("trial" or "discord"). He faced revolt, fought the inconclusive Battle of Siffin against Mu'awiya, the powerful governor of Syria and a kinsman of the murdered Uthman, and saw a faction of his own supporters break away in fury. In 661 Ali was assassinated—struck down in the mosque at Kufa by one of those extremists. Mu'awiya then claimed the caliphate, founding a dynasty and moving its capital to Damascus.

It is important to be precise about what the division is and is not. Sunni and Shia Muslims share the same God, the same Prophet, the same Quran, the same five daily prayers, the same fast of Ramadan, the same pilgrimage to Mecca. They agree on the overwhelming majority of the faith. The historic split concerns leadership and authority—who should have succeeded the Prophet, and where religious authority rightfully lies—and the distinct traditions of law, ritual detail, and remembrance that grew from that root over the centuries.

With Mu'awiya's victory, the capital of the Islamic world moved from the deserts of Arabia to the ancient, cosmopolitan city of Damascus, and the caliphate became, for the first time, a hereditary dynasty: the Umayyads. Some pious Muslims never accepted this transformation of the caliphate into a kingdom, and the Umayyads would always face the charge that they had turned a spiritual office into a family throne. But under them the Arab empire reached an extent the Roman world had never matched.

The conquests resumed on two fronts, east and west, until the empire stretched almost beyond imagination. In the east, Arab armies pushed across Persia into Central Asia—Bukhara, Samarkand—and reached the valley of the Indus, in what is now Pakistan. In the west, they swept along the North African coast to the Atlantic, and then, in 711, crossed the narrow strait into Europe.

At its height the Umayyad Caliphate ran from the Atlantic shore of Morocco and Spain to the fringes of India and China—one of the largest empires the world had ever seen, assembled in under a century. Its two ends marked the limits of the surge: in the west, the check at Tours in 732; in the east, the failure to take the walls of Constantinople in 717–718. The Byzantine capital, with its sea walls and its secret weapon of "Greek fire," would endure for another seven centuries.

The Umayyads did more than conquer; they built the machinery of a durable state. Under Abd al-Malik, Arabic became the language of administration across the whole empire, replacing Greek and Persian in the government offices, and the first distinctly Islamic coinage was struck—gold dinars bearing words instead of the images of rulers. A shared language, a shared coinage, and a shared faith began to knit a bewildering variety of peoples—Arabs, Persians, Berbers, Copts, Visigoths, Central Asians—into a single civilization.

Yet the empire's very success bred resentment. The Umayyads ruled as an Arab aristocracy, and non-Arab converts to Islam—especially the Persians, heirs to an older and prouder civilization—often found themselves treated as second-class Muslims, still taxed and slighted. Add the Shia, who never accepted Umayyad legitimacy, and the pious, who bridled at dynastic luxury, and the dynasty sat atop a mountain of grievance. In 750 that mountain moved. A revolution born in the east would sweep the Umayyads away—and carry the Islamic world's center of gravity with it.

The revolution that toppled the Umayyads gathered first in Khurasan, the great eastern province of Persia, where discontent ran deepest. Its leaders were the Abbasids, a family descended from the Prophet's uncle al-Abbas, and they promised what the disaffected longed to hear: a caliphate that would honor the Prophet's family and treat all Muslims—Arab and non-Arab alike—as equals. Beneath black banners, their armies swept west, and in 750 they defeated the last Umayyad caliph at the Battle of the Zab. The dynasty of Damascus was hunted down almost to the last man.

Almost. A single Umayyad prince, Abd al-Rahman, escaped across North Africa and made his way to Spain, where he founded an independent Umayyad emirate at Córdoba—a survival that would, in time, produce one of the most brilliant societies of the age. But in the heartlands, the Abbasids now ruled, and they set about remaking the empire in their own image.

The move eastward, from Damascus to Baghdad, was more than a change of address. It shifted the whole center of gravity of the Islamic world away from the Mediterranean and toward Persia and the East. The Abbasids drew deeply on Persian traditions of kingship and administration; their court adopted the ceremony, the bureaucracy, and much of the culture of the Sasanian emperors they had supplanted. Persian families like the Barmakids rose to run the state as viziers. The result was a genuinely cosmopolitan civilization—Arab in language and faith, but Persian, Greek, Indian, and Central Asian in learning and taste.

Baghdad's position made it rich. It sat astride the routes that carried silk and porcelain from China, spices from India, gold from Africa, and furs from the north. Its markets overflowed; its canals watered gardens and orchards; its harbor on the Tigris received ships from as far as the South China Sea. And crucially, the Abbasids had acquired, from Chinese prisoners taken after a battle in Central Asia in 751, the secret of a technology that would transform intellectual life: the making of paper. Cheap, durable paper replaced costly parchment, and Baghdad soon had paper mills, a booming book trade, and libraries. The stage was set for one of the greatest flowerings of learning the world had ever seen.

In the Baghdad of the Abbasids, something happened that has few parallels in human history: a civilization decided, deliberately and at enormous expense, to gather and translate the accumulated learning of every people it could reach. The caliphs and their courtiers sent agents to Byzantium, to Persia, to India, hunting for manuscripts—works of philosophy, medicine, mathematics, astronomy, and engineering—and set the finest scholars in the world to rendering them into Arabic. It is remembered as the Translation Movement, and it ran for the better part of two centuries.

Its symbolic heart was the Bayt al-Hikma, the "House of Wisdom"—a library and center of scholarship in Baghdad, patronized above all by the caliph al-Ma'mun (reigned 813–833). Here Greek, Persian, Syriac, and Indian texts were collected, studied, and translated; here scholars of different faiths worked side by side. The historian's caution is worth a word: the exact nature of the House of Wisdom is debated, and it was probably more a library and translation bureau than a formal "university." But the movement it stands for was real, vast, and world-changing.

Consider what was preserved. Across the Christian West, in these same centuries, much of Greek learning had been lost—its libraries scattered, its language forgotten, its texts crumbling in a few remote monasteries. In Baghdad, that same learning was being hunted down, translated, corrected, and copied onto durable paper. Aristotle and Plato, Euclid's geometry, Ptolemy's astronomy, the medicine of Galen, the engineering of Archimedes—an enormous share of the intellectual inheritance of antiquity passed through Arabic, and would one day return to Europe by that road.

But the Islamic scholars were never merely copyists. From India they took something the Greeks had never had: a place-value number system with a symbol for nothing—zero—and a way of astronomy and calculation built upon it. From Persia they took traditions of statecraft, literature, and learning. From China, paper. And to all of it they added their own genius. The translated inheritance was a foundation, not a ceiling. Within a few generations, scholars writing in Arabic would push far beyond anything the Greeks or Indians had achieved—in algebra, in optics, in medicine, in astronomy. That is the story of the next two chapters.

If one chapter of this story deserves to be better known, it is this one. In the centuries around the year 1000, scholars writing in Arabic—Arabs, Persians, and others, Muslims and sometimes Christians and Jews—produced a body of scientific work that has left a permanent mark on the way every educated person on earth now thinks. Their names have been half-erased in the West, but their fingerprints are on the mathematics children still learn in school.

Al-Khwarizmi did something else of incalculable importance: he championed, in his writing, the number system he had learned from Indian sources—the nine digits and the crucial symbol for nothing, zero. This place-value system, in which the position of a digit gives its value, is so much more powerful than Roman numerals that it is hard to overstate the gap. Try multiplying MCMXLIV by XXIII and you will feel it. Through al-Khwarizmi and those who followed, these "Hindu-Arabic" numerals—the very 1, 2, 3, 4 you are reading—spread across the Islamic world and, centuries later, into Europe.

Then there was Ibn al-Haytham (c. 965–1040), known in Latin as Alhazen, perhaps the greatest physicist between antiquity and the seventeenth century. Working in Egypt, he wrote a monumental Book of Optics that overturned the ancient belief that the eye sends out rays to see; correctly, he argued that vision happens when light reflects from objects into the eye. More than that: he insisted that claims about nature be tested against controlled observation and experiment. Many historians regard his method—hypothesis, experiment, mathematical analysis, conclusion—as an early and rigorous form of the scientific method itself.

The list runs on. Muslim astronomers built great observatories, corrected Ptolemy, catalogued and named the stars—which is why so many bright stars still bear Arabic names: Aldebaran, Betelgeuse, Rigel, Vega, Altair, Deneb. Scholars like al-Biruni (973–1048) measured the Earth's radius with astonishing accuracy and wrote with rare fairness about the religions and sciences of India. Chemists refined the techniques of distillation and gave us words like alkali and alcohol. In hospitals called bimaristans, physicians treated patients, trained students, and kept records, in institutions that prefigure the modern teaching hospital.

A civilization is not only its science. The Islamic Golden Age was also an age of profound philosophy, of soaring poetry, of exquisite art—and of one of the great debates in the history of human thought: the question of how faith and reason are related, and what each can know.

The philosophers, the falasifa, took up the Greek inheritance and ran with it. Al-Kindi and al-Farabi wrestled Aristotle and Plato into dialogue with Islam; Ibn Sina built a vast philosophical system. But the confidence of the philosophers provoked a formidable challenge. Al-Ghazali (c. 1058–1111), one of the most influential thinkers in Islamic history, wrote a searching critique titled The Incoherence of the Philosophers, arguing that reason alone could not reach the deepest truths and that the philosophers had overreached. His own spiritual crisis and recovery, recorded in a candid autobiography, led him toward the inner, experiential path of the mystics.

Alongside the philosophers ran a very different current: Sufism, the mystical tradition within Islam that seeks direct, loving experience of God through remembrance, poetry, music, and discipline of the heart. Sufi orders spread the faith across Asia and Africa, often more effectively than any army, and Sufi poets gave the world some of its most beloved verse. Greatest among them was Jalal al-Din Rumi (1207–1273), whose long mystical poem, the Masnavi, remains one of the most read works of poetry on earth.

The visual arts of the age turned largely away from the depiction of living beings—especially in religious settings—and toward two glories instead: calligraphy and geometry. Because the word of God in the Quran was itself sacred, the writing of that word became the highest of arts; Arabic script bloomed into dozens of styles of breathtaking beauty. And the endlessly repeating geometric patterns and vegetal designs we call the arabesque—infinite, interlocking, without beginning or end—adorned mosques, palaces, carpets, and books, suggesting the infinity of the divine.

Far to the west, on the Iberian Peninsula, the fugitive Umayyad prince Abd al-Rahman had built, out of exile, a new home for his dynasty. The Muslim-ruled lands of Spain and Portugal—al-Andalus—would endure in some form for nearly eight centuries, and at their height they produced a society so cultured that a German nun writing in the tenth century called its capital, Córdoba, "the ornament of the world."

Al-Andalus is often remembered for its convivencia—the "living together" of Muslims, Christians, and Jews. The reality was complicated and should not be romanticized: it was a society with a clear Muslim ruling order, in which Christians and Jews were protected but subordinate, and it saw its share of tension, persecution, and war. Yet by the standards of the medieval world it was, for long stretches, remarkably plural and creative. Jewish culture in particular enjoyed a golden age of its own within al-Andalus, producing statesmen, poets, and the great philosopher Maimonides, born in Córdoba in 1138, who wrote his masterworks in Arabic.

Here is where the great circle closes. From the twelfth century, as Christian kingdoms advanced southward and captured cities like Toledo with their Arabic libraries intact, European scholars flocked to translate the treasures they found. In Toledo, teams of Christians, Jews, and Muslims rendered Arabic works into Latin—the science of al-Khwarizmi and Ibn al-Haytham, the medicine of Ibn Sina, and, above all, the Aristotle of Averroes with his commentaries. The tireless Gerard of Cremona alone is credited with translating scores of works. Through this Spanish gateway, the accumulated learning of the Islamic Golden Age—much of it the rescued and enlarged inheritance of Greece—poured into a Latin Europe hungry to receive it.

It is easy to imagine the Islamic world as a single empire, but by the tenth century it was nothing of the kind. The caliphate had fragmented into rival states and dynasties; at one point three men in three cities—Baghdad, Cairo, and Córdoba—all claimed the title of caliph. What held this vast, divided world together was not a single government but something subtler and stronger: a shared faith, a shared language of learning, a shared law, and the greatest network of trade routes the pre-modern world had ever known.

Muslim merchants carried goods and faith along the Silk Roads to China, across the Indian Ocean on the monsoon winds to India and Southeast Asia, and across the Sahara—that "sea of sand"—to the kingdoms of West Africa. Islam spread, in most of Asia and Africa, not by conquest but by commerce and the quiet persuasion of traders and Sufi teachers. This is why the country with the most Muslims today is not in the Middle East at all, but in Southeast Asia: Indonesia, reached by merchants, not armies.

Meanwhile, in Egypt, a rival caliphate had arisen. The Fatimids—a Shia dynasty claiming descent from the Prophet's daughter Fatima—conquered Egypt in 969 and founded a new capital beside the old Roman fortress on the Nile. They called it al-Qahira, "the Victorious"—the city we know as Cairo. It would grow into one of the greatest cities of the Islamic world and remains one of the largest cities on earth.

From the sands of Mali to the spice ports of Indonesia, from Cairo's al-Azhar to Timbuktu's Sankore, the Islamic world of these centuries was a single vast conversation—of merchants and pilgrims, judges and mystics, students and scholars—conducted in a hundred tongues but bound by one faith and, for the learned, one language. A traveler like the Moroccan Ibn Battuta, who in the fourteenth century wandered some 75,000 miles from Morocco to China and back, could cross this whole world and find, almost everywhere, a mosque to pray in, a scholar to talk with, and a law he recognized.

No golden age lasts forever. In the eleventh, twelfth, and thirteenth centuries, the Islamic world was struck by two great shocks from opposite directions—one from the west that it ultimately weathered, and one from the east that it barely survived.

The first came from Latin Christendom. In 1095 Pope Urban II called on the knights of Europe to march east and wrest the Holy Land from Muslim rule, and in 1099 the armies of the First Crusade stormed Jerusalem, massacring much of its population and founding a string of Crusader states along the eastern Mediterranean. For the Islamic world, the Crusades were at first a bewildering intrusion by rough Frankish warriors from a Europe most Muslims regarded as a backward frontier. Over nearly two centuries of intermittent war, the Crusader states were slowly worn down.

But the Crusades, for all their fury, were a wound the Islamic world could absorb. The blow that fell from the east was of another order entirely. Out of the steppes of Central Asia came the Mongols—the vast cavalry armies unleashed by Genghis Khan and his heirs, the most formidable military force the medieval world had ever faced. (Their extraordinary story is told in its own right in our Mongol Empire narrative.) In the 1250s, Genghis Khan's grandson Hulagu led a Mongol host into the Islamic heartlands with orders to bring the whole region under Mongol rule.

The fall of Baghdad in 1258 is often taken as the symbolic end of the Islamic Golden Age. The Mongol tide was finally halted two years later, in 1260, when the Mamluks of Egypt—a remarkable state ruled by an elite of former slave-soldiers—defeated a Mongol army at the Battle of Ain Jalut in Palestine, the first major check the Mongols had suffered. The Mamluks would go on to finish off the last Crusader strongholds and to make Cairo the new center of Islamic power and learning, giving refuge to scholars fleeing the ruin of the east.

It would be wrong, though, to imagine the light simply going out. The Mongols who conquered the Islamic lands would, within a couple of generations, largely convert to Islam themselves—a stunning reversal in which the destroyers were absorbed by the faith of the conquered. Scholarship, art, and science continued; some of the finest Islamic astronomy was done under Mongol patronage at the observatory of Maragha. But the age of a single, dazzling center at Baghdad was over. The Islamic world would rebuild—and, in time, rise again in new forms.

The destruction of Baghdad was an ending, but not the ending. Out of the wreckage of the old order, and across the following centuries, the Islamic world reorganized itself around new powers—and in the early modern age it produced three of the most magnificent empires on earth, each so wealthy and cultured that historians sometimes call them the "gunpowder empires." Their full stories belong to other pages; here we sketch them only as the horizon toward which our tale runs.

To the east rose the Safavid Empire of Persia, founded in 1501 by Shah Ismail. The Safavids made Shia Islam the state religion of Iran—a decision whose consequences shape the religious map of the Middle East to this day, for Iran remains the great heartland of Shia Islam. Their capital of Isfahan, rebuilt in the seventeenth century around a vast royal square framed by tile-covered mosques and palaces, was so beautiful that Persians said "Isfahan is half the world."

Southeast, across Persia and Afghanistan, lay the third jewel: the Mughal Empire of India, founded in 1526 by Babur, a descendant of both Genghis Khan and the conqueror Timur. The Mughals ruled a vast, overwhelmingly Hindu land with a Muslim dynasty, and at their best—especially under the emperor Akbar (reigned 1556–1605)—they pursued a policy of tolerance and cultural fusion that produced glories of art and architecture. The most famous of all stands at Agra: the Taj Mahal, a tomb of white marble built by the emperor Shah Jahan for his beloved wife, and perhaps the most recognized building on earth.

These empires carry our story to the threshold of the modern world. They were not a decline but a magnificent second act—centers of art, poetry, and power that dazzled the visitors who reached them from a still-rising Europe. Their later histories—of contact, rivalry, and eventual retreat before European empires—belong to another telling. What matters here is the shape of the whole: a faith born in one desert town had become, a thousand years on, the organizing force of three great empires spanning from the Balkans to Bengal.

Begin with the words. When you do algebra, you speak Arabic; when you follow an algorithm, you say the name of al-Khwarizmi. When you write a number using zero, or call something a cipher, you are echoing the Arabic sifr. Alchemy and chemistry, alcohol and alkali, admiral and arsenal, magazine and tariff, sugar and coffee and lemon, cotton and sofa and mattress—all came into European languages from Arabic. Look up at the night sky and read the names of the stars: Aldebaran, Betelgeuse, Rigel, Vega, Altair, Deneb. They are the words of the astronomers of the Golden Age, and they are still, quietly, on every star chart in the world.

Behind the words lies the larger debt. For the centuries when much of Europe had lost its grip on the learning of antiquity, the civilization of Islam gathered that learning up, translated it, corrected it, and enlarged it—and then handed it on. The mathematics, the medicine, the philosophy, and the recovered Aristotle that helped ignite the European Renaissance came, in enormous measure, through Arabic, by way of Toledo and Córdoba and Sicily. There is a real sense in which the modern West is a debtor to the medieval East. The scholars of Baghdad and Córdoba were not a footnote to the story of human knowledge; for a long span, they were the story.

And the faith itself endures—not as a relic of the Golden Age, but as one of the great living forces of the world. From that first word in the cave of Hira, "Recite," Islam has grown into the religion of nearly two billion people, on every continent, in every kind of society: the second-largest and among the fastest-growing faiths on earth. Its call to prayer sounds five times a day across a vast arc of the globe, and every year some two million pilgrims converge on Mecca, circling the Kaaba as pilgrims have for fourteen centuries—an unbroken thread from the world of Muhammad to our own.

It had begun with an orphan in a desert town, a man so honest his neighbors called him trustworthy, sitting alone in a cave with the whole of history about to change. It became a message that united the tribes of Arabia, an empire that spanned three continents, and a civilization that, for centuries, held the lamp of learning higher than anyone else on earth. That is the story of the rise of Islam and its Golden Age: how a word spoken in the wilderness grew into one of the great shaping forces of human civilization—and how, in preserving the wisdom of the past, it helped light the way to the future.