The ferocious Mongol conquests from 1206 led by Genghis Khan created the largest land empire in world history. The trademark of this tribal confederation of nomadic, mounted archers from the arid steppe was the merciless slaughter of defeated populations and their domesticated animals, wholesale pilfering, and razing of cities, irrigation works, and other vital infrastructures of civilized life. When Genghis died, undefeated, in 1227 the Mongol empire spanned the entire central Asia steppe from the Volga River in the west to the Amur River in the east. His successors expanded into eastern Europe as far as Poland and Hungary by 1241. Much of the Islamic Middle East capitulated to Mongol warriors, who in 1258 savagely destroyed Baghdad and its caliphate. Mongol armies reached the Adriatic by 1258 and the edge of Africa by 1260. By 1279 all of China was in Mongol hands, the first time in history that China was ruled completely by foreigners. The zenith of the Mongol empire was reached under Genghis's able grandson, Khubilai Khan, who ruled from 1260 to 1294. He set up China's Yuan dynasty, which had its seat of government in Beijing. It was Khubilai's Mongol-led China that Marco Polo served and famously described to the transcriber of his Travels, Travels, Rustichello of Pisa, while the two languished in a Genoa prison after the Venetian galley on which Marco had been traveling was captured during a September 1298 battle between Mediterranean trade rivals Venice and Genoa. Rustichello of Pisa, while the two languished in a Genoa prison after the Venetian galley on which Marco had been traveling was captured during a September 1298 battle between Mediterranean trade rivals Venice and Genoa.
The Mongol conquests were to be world history's last great wave of invasions by nomadic, pastoralist warriors that had disrupted and challenged the settled, civilized lifestyle since the Bronze Age. Before the Mongols, the water-fragile central Asian steppes had produced invasions from bellicose confederations of Hsiung-nu, Juan-juan, and the Mongol's close cousins, Turkmen; the latter allied with China in defeating the Juan-juan in the mid-sixth century, and subsequently divided into two groups and eventually infiltrated and rose to political prominence in Islamic society. The nomads' ignorance of civilization's complex technologies, including sophisticated water management, proved to be one of their grave weaknesses in trying to govern the societies they conquered. The rule of the Mongol's Tartar predecessors, for example, had been undermined by a decline in canal traffic capacity and related diminution of iron and agricultural production, resulting from their failure to undertake timely restorations when the flooding Yellow River burst its restraining dikes in 1194 and cut a new path to the sea.
Well into the thirteenth century the Mongols themselves still crossed rivers using primitive, inflated skins and rafts. Their conquest of southern China succeeded after forty-five years only when a former Sung commander, Liu Cheng, defected to Khubilai and built a river naval fleet capable of challenging Sung dominance of the Yangtze River. The decisive confrontation was a five-year river-and-land siege of Hsiang-yang, a key river fortress that controlled the main access route to the Yangtze heartland. When success came in 1273, south China finally lay open to the Mongols. With its cavalry bogged down in muddy rice fields, its infantry unfamiliarly led the invasion. The final remnants of Sung resistance were extinguished in early 1279 following their large naval defeat off the coast of Canton, when a loyal minister jumped in the ocean, drowning himself along with the last imperial prince.
Even then, the Mongol Yuan dynasty had very limited success exploiting the rich potential of China's water resources. Despite building an impressive naval fleet, Khubilai was unable to extend the Mongol's military land prowess to sea power, as exemplified by the unsuccessful large naval invasions against Japan in 1281 and Java in 1293. He failed as well to wrest ocean shipping from the Muslims. Like his predecessors, Khubilai devoted high priority to enhancing the Grand Canal. He restored the connection to the Yellow River, disrupted by the course change of 1194, straightened the canal, and added a northern extension to his new capital, Beijing, on the extreme northeastern frontier. Food security and prosperity increased. Yet his engineers failed to make the crucial canal innovation necessary to supply sufficient water to enable food transport ships to readily pass year-round over the summit level of the hills leading to Beijing. This contributed to the Yuan dynasty's downfall. Sea convoys temporarily mitigated the vulnerability, but finally piracy and rebellions in the south disrupted reliable food deliveries. The breakthrough "Heaven Well Lock" of the Grand Canal would be made during the restoration by the Ming dynasty, which finally toppled the despised, plague-weakened Mongolian Yuan after 1368.
Like many nativist restorations, the early Ming era was marked by a revival of old traditions, renewed economic and creative vigor, and xenophobia. Water engineering advances played a prominent role, above all in shipping, reconstruction of iron chain suspension bridges, and in major improvements of the Grand Canal. The Ming's superior command of water resources, in fact, had played a decisive role in driving the Mongols back into the northern steppe. In 1371 the Ming navy, armed with iron prows and firearms, broke through the chains and bridge of boats defending the gorge at Chu-tang, the key to controlling Sichuan.
Once in power, Ming seagoing vessels, meanwhile, reopened a 500-mile-long transport supply line of food, clothing, and weaponry that enabled the reconquest of southern Manchuria. Once victory was secured, this sea convoy from the south, manned by some 80,000 men, rapidly became an indispensable lifeline to supplying rice to Beijing and the Ming's northern defense lines. When the Ming relocated its own capital seat to Beijing in 1403, it simultaneously launched an enormous, state-run shipbuilding program to secure its control over the vital sea-lanes. Between 1403 and 1419, the shipyards near Nanking alone turned out 2,000 ships. The Ming fleet featured 3,800 ships by 1420, including 250 giant, long-distance "treasure ships," some up to 440 feet long and 180 feet wide, with square linen sails on four to nine masts towering up to 90 feet high, capable of carrying 450 to 500 sailors and displacing up to 3,000 tons apiece-ten times more than the flagship Vasco da Gama sailed in his historic voyage around the Cape of Africa into the Indian Ocean at the end of the century. The ships incorporated all China's advanced innovations, making it the supreme naval power of its time.
The Ming soon exercised their new sea power with a series of spectacular maritime expeditions that revealed China's clear naval superiority in the great age of sail that was just dawning around the world. The most famous of these were the seven expeditions between 1405 and 1433 commanded by Admiral Cheng Ho, a Muslim and court eunuch devoted to the emperor. Cheng Ho's first fleet had more than twice as many vessels as the Spanish Armada 150 years later, and included 62 giant treasure ships. It far outclassed the Arab dhows and Indian vessels it met in the Indian Ocean. In his seven voyages, Cheng Ho's 27,000 man fleet easily established control in the Indian Ocean, over the Malacca Strait, Ceylon, and Calicut, India, and became an influential force at Hormuz at the mouth of the Persian Gulf. Cheng Ho also sailed up the Red Sea, where some Muslim crewmembers disembarked to undertake a pilgrimage to Mecca, and south along the East African coast as far as Malindi in modern Kenya, where he obtained a giraffe as a novelty present for the emperor in Beijing. In contrast with the European voyages in the Indian Ocean during the following century which were undertaken to secure treasure, profitable trade routes, and eventual military dominance, Cheng Ho's primary mission was instead to win homage for the glory and power of the Ming rule. Few dared resist his demands of honor for the "son of heaven" in Beijing when his warships appeared off shore. Gifts were diplomatically bestowed upon those who acquiesced. Resisters were militarily disciplined-but not massacred, as they were by Europeans three-quarters of a century later. When a ruler in Ceylon showed reticence, for instance, Cheng Ho had him seized and shipped back to China's Imperial Court for proper disciplining.
Then, in 1433, all the expeditions abruptly ended. Edicts from the emperor strictly limited Chinese seafaring and contacts with foreigners, the construction of oceangoing ships, and even the very existence of ships with more than two masts. Cheng Ho's great warships were left to rot. Naval personnel were redeployed to smaller ships that plied the Grand Canal. Eschewing its power, China turned inward, away from the world.
It was a remarkable moment in history when a great power, possessing all the means to dominate all worlds it encountered and with vessels seaworthy enough to cross all the open oceans, including the Pacific to the New World, suddenly decided not to press its advantage. Historians have mused how world history would likely have been radically different had the Portuguese encountered a powerful Chinese empire controlling the key ports and sea-lanes of the Indian Ocean when they rounded the southern African cape in 1498 to establish the world-changing direct ocean link between Europe and the East. Indeed, one cannot help but further wonder whether Europe itself might have been subordinated and colonized if, instead of cutting off from the world, China had applied its maritime and industrial superiority to press southward around Africa, to master the Atlantic Ocean wind and current systems, and announced itself to Europe and the Americas before Columbus and da Gama ever hoisted sail.
Why did China suddenly turn inward? Xenophobia and angst about the revival of Mongol power in the north, where the modern Great Wall was being built, were motivating factors. But the world-history-shaping about-face in China's geopolitical strategy was made possible, and also driven, by the successful completion in 1411 of the greatest of all Ming water engineering triumphs-the New Grand Canal. The dredging, repair, and expansion of the entire Grand Canal had become a top priority once the Ming government moved China's capital back to Beijing in 1403. By providing the means to supply the northern frontier's fortresses with food and munitions, the Grand Canal became the vital defensive artery for the entire country. The existing sea transport system was not reliable enough to provide the needed food supplies for the northern frontier due to piracy and the inherent natural uncertainties of sea travel. To move supplies along the inland Grand Canal extension to Beijing, however, the Ming had to devise one canal innovation that had stymied the Yuan engineers-how to supply enough water to enable perennial passage, even in the dry season, over the highest point in the hills. Often large cargo ships were sidelined for up to six months until water levels refilled with the seasonal rains. The breakthrough Heaven Well Lock was made in 1411. The new lock split the combined flow of two rivers and allowed managers to regulate seasonal water flows through a network of 15 locks. Heaven Well Locks were introduced along the length of the Grand Canal, which at a stroke became a reliable, all-season inland waterway and all-important supply line of the Ming dynasty. With the government employing 15,000 boats and some 160,000 transport workers, food supplies to the north rapidly quadrupled.
The sea transport supply route became redundant and was shut down. "With the re-construction of the Grand Canal to Peking (Beijing) in 1411, and the abolition of the main sea transport in 1415," China historian Mark Elvin observes, "the navy became for the first time a luxury rather than a necessity." After 1415, shipbuilding resources were diverted to the building of canal boats; after 1419 all ocean shipbuilding ceased. The decision to end Cheng Ho's expeditions after 1433 and rely exclusively on China's internal resources, therefore, was but another sequential step in the same inward political direction.
The completion of the New Grand Canal proved to be the decisive turning point that enabled China to make its history-changing policy U-turn and cut off from the rest of the world. Moreover, by artificially creating a more self-contained, command-controlled, hydraulic environment, the New Grand Canal also enhanced the centralized authority of the Ming state. The emperor and his conservative neo-Confucian mandarins, in alliance with the landed agricultural interests, used this power to suppress the surviving private merchant class that had been such a vibrant component of the Sung golden age. This contrasted starkly with contemporaneous developments in Europe, where the absence of a unifying inland waterway system and the focus on transport by sea helped produce smaller states, whose competition led to the expansion of unregulated trade and free-market enterprise.
Although economic growth continued after the mid-fourteenth century, China's inner dynamism and creative inventiveness gradually declined. This also helped illuminate the second historical enigma why it was that industrially advanced medieval China, possessing virtually all the requisite scientific know-how, did not make the next advances to create modern industrialism hundreds of a years before the decisive breakthroughs were finally achieved in the West. A key part of the answer, simply put, was that the reassertion of a strong, isolationist, centralized state inhibited the emergence of a market-driven economic engine that in eighteenth century England ultimately combined the profit motive with innovations in technology to make the breakthroughs that fueled the Industrial Revolution. Another part of China's failure to achieve early industrial takeoff also stemmed from the chronic surfeit of cheap manpower resulting from the dense populations produced by its rice farming society. This diminished both the political and economic incentives to develop labor-saving technologies, such as the steam engine, whose catalytic synergies with iron were to drive the early industrial age.
China's isolation lasted almost four centuries. Yet by trying to preserve its ways without engaging the innovative ferment of the outside world, it made itself vulnerable, once again, to external incursions. Just how far China had fallen behind technologically was stunningly demonstrated by mobile British steam gunboats during the first Opium War of 1839 to 1842, which forcibly reopened the helpless empire to the world. China's foreign trade contacts at the time were restricted to a single port, Canton. Seeking a way to balance a lopsided trade pattern favoring Chinese exports to the West of tea and other luxuries, the British had gradually cultivated a Chinese market for opium grown in its Bengal, India, colony. As Chinese opium addiction, and with it opium imports, mounted, Chinese officials in 1839 resolved to interdict importation of the drug. At first they appealed to England to halt its opium exports. With unimpeachable logic, they noted in a letter to Queen Victoria that opium was banned in England and that the same principle should apply to China. To the British, however, moral or legal consistency was subordinate to its mercantile and colonial interests. The Chinese implorations were rebuffed. In an act reminiscent of America's Boston Tea Party, Chinese officials seized some 30,000 chests of drugs from British and other European merchants and dumped many into the river. Britain's response was to dispatch a fleet of cannon-armed, paddle-wheel, steam gunboats to the mouth of the Canton River in June 1840. To the amazement of the Chinese, the steamboats seemed to have the power to fly across the water, regardless of wind or current. It took only half a dozen skirmishes for Britain to win the Opium War. British steamers sailed up Chinese rivers, entering the Yangtze River to take Shanghai and then the strategic choke point where the Grand Canal met the great river. When Nanking was threatened in August 1842, China capitulated to Britain's unequal and humiliating treaty terms. In addition to indemnities for merchant losses, the Chinese were compelled to cede in perpetuity to Britain the barren island of Hong Kong and to open five port cities to the free trade of low-cost British merchandise, which Britain reasonably expected would help enrich its world-class manufacturers. France and the United States soon demanded and received similar rights; the second Opium War in the late 1850s ended with Anglo-French forces occupying Beijing, more port openings, and the right of foreigners to travel inside China, including having diplomatic representatives dispatched to the emperor's Forbidden City at Beijing.
The humiliating defeat in the Opium Wars rendered publically visible the extent of the demise of China's 2,000-year-old empire. It added insult to the widespread disaffection with the ineffectual government and helped stir the rebellions that ultimately toppled it. A telltale sign and fomenter of this internal decay was once again waterworks deterioration. Millions died in three major dike breaks in the Yellow River between 1841 and 1843. In 1849, the worst flood in a century ravaged the lower Yangtze. The major shift of the Yellow River toward its present northern course in the 1850s caused major breeches in the Grand Canal. Northern sections of the canal were left unrepaired and the critical channel supplying Beijing was abandoned altogether following the Taiping Rebellion and other major uprisings in the 1850s and 1860s. Floods worsened in the late nineteenth century due to inadequate diking and waterworks maintenance, hastening the final days of the ruling Manchu dynasty and the long Chinese empire in the 19111912 revolution. The revival of the Grand Canal and other major water infrastructure, reminiscent of the restoration of new dynasties, began with the coming to power after a Japanese occupation and long civil war of the postWorld War II Mao Zedongled communist regime.
CHAPTER SIX.
Islam, Deserts, and the Destiny of History's Most Water-Fragile Civilization Golden age China overlapped and exchanged goods with a young, trading-based civilization that had emerged improbably out of the sparsely populated, parched desert of the Arabian Peninsula under the inspirational organizing banner of a new religion, Islam. During Islam's brilliant flowering from the ninth through twelfth centuries, its civilization held sway over an extensive domain stretching from Spain in the west, across North Africa, south from Egypt along the East African coast to the Zambezi River near modern Mozambique, east from the Levant to the Indus River, and northeast in central Asia beyond the Oxus River to the western borders of the fabled Silk Roads. The riches underpinning its illustrious civilization came from its control of the Old World hub of long-distance land and sea trading routes linking the civilizations of the Far East, the Near East, the Mediterranean, and sub-Saharan Africa.
From its stunningly rapid rise to its puzzlingly abrupt fall from history's center stage, the signature characteristics and historical destiny of Islamic civilization were overwhelmingly dictated by the challenges and responses to its scarce natural patrimony of freshwater. Islam's core habitat was a desert surrounded by two saltwater frontiers, the Mediterranean Sea and the Indian Ocean. Precious few fresh hydraulic resources watered its interior. Its deserts contained scattered date-palm-shaded oases, underground springs and wells, and some seasonal wadis. Only a few large rivers-such as the Nile, the Tigris-Euphrates and to a much lesser degree the Jordan-were capable of sustaining intensive irrigated agriculture and the civilized, urban life that clustered around it. No navigable river or artificial waterway like China's Grand Canal spanned the long distances of arid emptiness between water sources to unify and centralize the Islamic world's political, economic, and social centers. Its noted dearth of small, perennial rivers-its so-called stream deficit-additionally made freshwater an omnipresent natural resource challenge for drinking, irrigation, transport, and waterpower that put great stress on the population-resource balances of Islamic society in all but a few privileged locations.
Islamic World & Selected Trade Routes Constantinople [image]
Freshwater scarcity, in short, effectively rendered Islam a water-fragile civilization, extremely vulnerable to changes in natural and engineered hydrological conditions. As a result, its periods of abundance were temporary and its sufficiency rarely enduring. For centuries, the dearth of freshwater in its original Arabian habitat had been the primary obstacle confining its inhabitants to bare subsistence lifestyles. The Arab genius in transforming the obstacle of the hot, dry deserts, and subsequently the salty sea frontiers, into near-monopoly highways of trade was the key catalyst that launched Islam's hallmark rise to greatness as a civilization controlling the long-distance movement and transit between East and West. Its precarious hydrological foundations also ultimately helped explain why its preeminence unraveled so quickly after the twelfth century.
Islamic civilization started with Muhammad, founding prophet of its monotheistic religion and revealer of the Koran, its holy book. Arabians at the time were polytheistic animists with strong tribal social structures. Many were still nomadic pastoralists, raising camels and raiding trade caravans. Settled life at the sporadic oases supported only very small populations. One important settlement, Mecca, was built around a spring with "bitter," or salty, tasting water, and had only about 20,000 to 25,000 inhabitants. Mecca was located at an important restocking juncture for water and other supplies along the historic camel caravan trade route that carried frankincense, myrrh, and other luxuries between Yemen and the Mediterranean ports of the Levant. It was also specially advantaged because it was a regular destination of Arab pilgrims who came to venerate a black meteorite that had fallen nearby in antiquity and was regarded as divine.
Legend and Muhammad identified the origin of the Semitic Arabs as descendants of Ishmael, Abraham's son by his maid-concubine, Hagar. From the beginning, water was always highly esteemed in both desert Arab and Islamic society. By tradition, no man or beast can be denied access to drink from a man's well; the very transliteration of shari'aa, or Islam's governing religious law, means "the way" or "path to the watering place." Muhammad himself was born around 570 into a reputable but weaker clan of Mecca's leading Quraysh tribe. Many Quraysh were merchants who had leveraged the power from the tribe's control of water rights for the pilgrimage into lucrative participation in the camel caravan trade. Orphaned at a young age, the uneducated Muhammad grew up in the caravan trading business of his uncle and clan elder, Abu-Talib. Historians believe he traveled outside Arabia along the trade routes, where he encountered many new ideas and religions. At age twenty-five, he married a rich older widow with caravan business interests.
Everything was quite unexceptional about the life of Muhammad until about the age of forty. Then one night, in 610, while sleeping in a cave outside of Mecca, he had a supernatural experience. He had a vision of the Archangel Gabriel summoning him to be God's chosen emissary and to begin reciting the first part of His revelation. For much of the next decade, Muhammad preached to a small group of followers, asserting that he was the final prophet in a line of divinely inspired Jewish and Christian messengers from Abraham, Moses, and Jesus. Islam meant simply a "submission" to God in all facets of life. As his following grew, the leading families of the Quraysh tried to suppress him. Muhammad's position in Mecca became untenable when his uncle and tribal protector died in 619. Some of his adherents fled for Christian Ethiopia. In 622, Muhammad and a group of followers left Mecca for a settlement 200 miles north at the crowded, sweet water oasis of Yathrib, later renamed Medina, or "city of the prophet," where he'd been invited to arbitrate disputes between local tribes.
From Medina, Muhammad's power base grew rapidly. He expelled Medina's Jewish tribes when they refused to acknowledge him as the true prophet. To supplement the limited agricultural resources of the oasis, he led his followers to raid camel caravans from Mecca in an expanding alliance with converted Bedouins, who shared profitably in the stolen booty. Before long, Muhammad was engaged in armed struggle with the Quraysh, possibly over control of trade routes. Several victories reinforced the religious fervor of the Muslim faithful that God was on their side, and gradually convinced Meccan leaders to negotiate the peaceful submission of Mecca to Islam by 630. As Mecca's new leader, Muhammad abolished all blood and property privileges except custodianship of the cube-shaped Ka'bah shrine housing the black meteorite. Mecca replaced Jerusalem as the holy focal point of Muslim prayers.
Through control of the oases, marketplaces, and key caravan and trade routes, plus diplomacy backed by several military offensives, Muhammad rapidly united most of the tribes of the Arabian Peninsula under the banner of Islam. Yet when Muhammad died in 632 many of the tribal chiefs considered their oaths to Islam no longer binding and rebelled against the financial tribute Medina exacted from them. The first caliph, or "successor" to Muhammad, Abu Bakr, responded by organizing a regular army to quell the rebellions. The momentum of these military successes launched a growing Islamic fighting force of fierce nomadic tribesmen who soon reached the frontiers of Arabia's great neighboring empires, Byzantine Rome and Sassanian Persia.
Under the ambitious and strong-willed second caliph, Omar, Arab armies surged across these frontiers and unleashed one of world history's astonishing military juggernauts. Long-standing borders were swept away with stunning speed and world history's cultural map was permanently transformed by seeding Islam throughout the conquered territory. One of the earliest and greatest victories was the August 636 battle of the Yarmuk River, a tributary of the Jordan River at the modern border of Syria, Jordan, and Israel. Aided by a dust storm that concealed their approach and fired by the zeal of religion and the lavish booty of imperial conquest, a large Arab army decimated a huge Byzantine force that became trapped with its back to the river, which soon ran bloody with its dead. By 642 Islamic armies controlled all of Syria and Palestine as well as Egypt's Nile Valley-thus severing Byzantine Constantinople from two of its richest provinces. Other Arab armies meanwhile thrust eastward, seizing Mesopotamia and the wealth of its twin rivers by 641. By 651 the entire Sassanian Persian Empire had succumbed with astonishing ease. The historic border between Rome and Near East empires, stable for some 700 years, was obliterated in just fifteen years.
Historians have offered various explanations for the spectacular and improbable success of the small, modestly equipped Islamic armies against the huge Persian and Byzantine empires. Although both maintained the facade of imperial power, the two old empires had become internally enfeebled by wars, disease, political struggles, barbarian invasions, and economic corrosion from their failure to maintain agricultural water management infrastructure. In Persia, internecine political quarrels had weakened the central administration, which also failed to maintain the river-fed irrigation systems on the Tigris and Euphrates that had supported the original rise of its power. The resulting fall in crop yields undermined the society's cohesion. The Byzantine grip on Egypt had been weakened by a century of low Nile floods during which land under cultivation had shrunk by half. The consequent famine, and an overlapping plague, had diminished Egypt's population by the time of the Arab invasions in 639 to merely 2.5 million-half its Pharaohic height. The highly organized, religiously inspired Arab armies also created their own advantages, notably by the use of camel transport which helped them attack effectively over wide areas. In a typical battle, camels provided the supply trains until preparations were ready for horses, mounted by sword-brandishing cavalry, to make the final charge.
Islam's military expansion continued, albeit at a less prodigious pace, following a power struggle and civil war that ended with the assassination in 661 of the fourth caliph, Ali. This was a seismic event in Islamic history. Islam's ruling caliphate moved from Medina to Damascus, under the hereditary control until AD 750 of the Quraysh's powerful Umayya clan. Moreover, Ali had been Muhammad's cousin and husband of his daughter, Fatima. His demise ignited the bloody schism between establishment Sunni and dissident Sh'ia, who believe that legitimate leaders of Islam should descend only from the prophet's direct household.
Under the Umayyads, North Africa was slowly brought into the Islamic fold. Aided by its new Berber allies-and in ships loaned by the Christian Byzantine Empire-Islamic soldiers crossed the Strait of Gibraltar to easily overthrow in 711 the Catholic Visigothic kingdom in Spain. The western Mediterranean, dominated by Rome in its heyday, was transformed into a Muslim lake. Arab fleets also became a force to be reckoned with in the waters east of Sicily and Malta. On land, raiders skirmished with Europeans deep into northern France over the next quarter century. In the east, Muslim armies crossed the Hindu Kush Mountains and stormed the Indus Valley between 708 and 711. The Caucasus mountains and the rich Oxus valley became the northeast borders of Islam's empire following a Muslim defeat at the hands of Turkish steppe tribe warriors-many of whom were later converted to Islam-and a Muslim victory over a T'ang Chinese army at the Talas River in 751, an event which effectively closed the overland Silk Roads and diverted its trade to the Indian Ocean. Islamic armies also marched south along the African coast. By ejecting the Abyssinian Christians from the narrow Strait of Aden (the modern Bab-el Mandab), they took control of its tolls and opened up the entire Indian Ocean to Arab shipping. Large Arabian dhows were soon sailing the Indian Ocean's two-way, seasonal monsoons and currents as far as Malacca and China and back again, and displacing Hindu shipping throughout the Old World's richest long-distance-trading ocean.
By AD 750 Islam's empire effectively had attained its largest geographical reach. It was a far-flung and decentralized empire with several competing regional centers and political interests loosely unified by a common religion, a common Arabic language, and enormous wealth derived from an extensive land and sea trading market economy. By one estimate the caliphate's revenue was no less than five times greater than the Byzantine Empire's by 820.
It was Islamic civilization's meager freshwater patrimony for farming that compelled it to pursue its livelihood through trade and commerce by exploiting its occupancy of the lands at the crossroads of the civilized Old World. Its agriculture was confined to three main types of cultivation and habitats. Along the sandy coastlines where annual rainfall exceeded seven inches the olive tree provided nourishment, cooking oil, and lighting fuel. Around the scorching desert oases with temperatures of at least 61 Fahrenheit flowered the remarkably useful date palm with its eatable fruit, fibrous leaves for weaving, and trunk for scarce wood. Only in the few irrigable river valleys, or on plains where more than 16 inches of rain fell each year, could the basic grains for Islam's daily bread be cultivated. In between the expanses separating these agricultural pockets roamed small clans of nomadic, seasonal groundwater and grass-seeking desert pastoralists who bred camels and other animals that provided the milk, meat, clothing, and tent skin mainstays of their simple, subsistence lifestyles.
Freshwater scarcity thus profoundly shaped the nature, institutions, and history of Islamic society. Water imposed constraints on food production and set limits on the maximum size of Islam's sustainable population. For instance, in its halcyon days, Islam could support only 30 to 50 million people; at the time, China's population was triple that number and world population was ten times greater. As a result, Islam was a civilization that chronically lacked manpower and was forced to expand through religious conversion and conquest. Islam's religious universalism and Arab leaders' eventual acceptance of non-Arab converts were likewise shaped by this demographic shortfall. So was the unusual degree of tolerance with which conquered peoples, mercenaries, and even its large slave population were absorbed into its society.
Freshwater scarcity also forced Islam's population to be highly concentrated around each region's few good water sources. Overcrowded towns of exceptional size and a few cities of dazzling, world-class accomplishments, such as Baghdad, Cairo, and Cordoba, were characteristic of Islamic society. Typically, a grand mosque surrounded by commercial markets lay at each town center, which was encircled by a web of twisty, narrow, and unsanitary streets built on slopes from which the rare rains would wash away the refuse.
At the height of its glory, three disparate, rival regional power centers arose-Spain-Magrib, Egypt-Levant, and Mesopotamia-Persia-reflecting and magnifying the religious and tribal divisions within Islam. In such decentralized circumstances, economic organization by command was impossible. Instead, it was the invisible hand of market forces that governed the signature transit and trade that held together Islam's economy and helped stimulate the breakthroughs underpinning its civilization's rise. "Not being well endowed by nature," observes historian Fernand Braudel, "Islam would have counted for little without the roads across its desert: they held it together and gave it life. Trade-routes were its wealth, its raison d'etre, its civilization. For centuries, they gave it a dominant position."
Water scarcity presented the primary obstacle standing between Islam and its historic rise to greatness through trade. First and foremost, it needed a way to cross the long expanse of its own hot, waterless interior deserts. Its first triumphant innovation, which at a stroke transformed the barren desert barrier into an insulated, exclusive Islamic trade highway, came by its disciplined organization of the hardy camel, with its prodigious water-storing capacity, into long trade caravans and military supply transports. A caravan of 5,000 to 6,000 camels could carry as much cargo as a very large European merchant sailing ship or a fleet of barges on China's Grand Canal. Islam's quasi-monopoly over this powerful pack animal provided it with the mobility to cross and exit its desert homelands-and to make its mark on world history.
The one-humped Saharan dromedary was specially adapted for the hot deserts. It could go without drinking water for a week or more, while plodding some 35 miles per day across the desert sands with a 200-pound load on its back. Water was stored in its bloodstream-its fatty hump, which grew flaccid during long journeys without nourishment, functioned as a food reserve-and it maximized water retention by recapturing some exhaled water through its nose. Once at a water source the camel speedily rehydrated by consuming up to 25 gallons in only ten minutes. It even could tolerate briney water. It possessed an uncanny memory for the location of water holes. Moreover, it could eat the thorny plants and dry grasses that grew on arid lands and were indigestible by most other animals. During a trip, camels could lose one-quarter their body weight, twice the amount fatal to most other mammals. The camel's extraordinary physical attributes made it possible for caravans to make the two-month, trans-Sahara trip from Morocco to Walata at the frontiers of the Mali Empire in Africa, which included one notorious stage of ten waterless days.
Like seas, deserts have played a distinctive role in history as expansive, empty spaces between distant civilizations. Initially, both imposed formidable geographic barriers of separation. But when traversed by some transport innovation, they were rapidly transformed into history's great highways of invasion, expansion, and cultural exchange that often abruptly realigned regional and world orders. Camels took Arab merchants and soldiers everywhere. Ultimately they reached Islam's other great water challenge-the frontier of its seashores. Islam's second water breakthrough was to extend its overland desert trade franchise to mercantile mastery of the Old World's great sea waterways, the Indian Ocean and much of the Mediterranean Sea. Its large dhows, their hulls made of planks tied together with date palm or coconut tree fibers and propelled by triangular lateen sails, which were highly maneuverable against headwinds, and steered with nimble stern rudders, became the caravans of the seas that carried Sinbad the Sailor on the adventures described in the classic literary cycle The Thousand and One Nights The Thousand and One Nights.
The long-distance trade route from the Moluccas or Spice Islands of Indonesia across the Indian Ocean to India and the West became in Muslim times the single greatest highway to world power and empire. At a time before Europeans had unlocked the secret arts of sailing across the open oceans and discovered the riches of the New World, and when the Silk Roads were closed, Arab dhows carried the lion's share of the world's most desirable goods and spread Islamic civilization throughout the richest coastal ports of call in the world.
Thanks to the Indian Ocean's unique, seasonally reversing wind system, Arab seamen could set out with a full load of goods between April and June by following the southwesterly monsoons, arrive within two months, do their trading, and fill up their cargo holds with profitable Oriental luxuries in time to catch the reliable fair winds from the northwest that would carry them home when cooling meteorological conditions reversed the monsoon's direction in winter. Arab vessels also plied the Mediterranean Sea from Spain to Alexandria and the Levant. Compared to the Indian Ocean, however, the Mediterranean's seaports offered far less alluring wealth while its unidirectional west-to-east winds made sailing more difficult.
By integrating its command over the resources of two disparate water environments-the waterless desert and the salty sea-Islam's influence soared. Camels and dhows defined its seamless land and sea caravan network that could transport goods and people between the four corners of the Old World. Disassembled dhows were transported by camel across the Sahara Desert for assembly and launch, camels and all, across the Red Sea. Once on the Arabian Peninsula, the ships were again disassembled and portaged for the long, landward rest of the journey along the wadis and oases to the ports of the Arabian Sea that led to the Indian Ocean. The preference for this laborious overland route was that for centuries the rocks and coral reefs, unpredictable winds, irregular currents, and pirate-infested waters of the deep, salty Red Sea were more perilous to navigate than the great deserts along its coasts. Many of the seaways and coastlines leading to the Indian Ocean's fabulously rich sea-lanes also were inhospitable and dangerous for seafaring. Arabia's absence of navigable rivers and its scant number of good harbors with sufficient freshwater made supplying ships extremely difficult; the lack of wood resources in the arid landscape was a second, water-related impediment. Adding to the navigational problems for seamen, the Arabian coast was notoriously stormy.
Islamic merchants nevertheless overcame these water obstacles. In Mesopotamia goods went by river to Baghdad, then overland west to Syria and Egypt, north to Constantinople and Trebizond on the Black Sea, and east through northeastern Iran and thence to central Asia and China. Gold and slaves from Sudan, Oriental silk, peppers, spices and pearls, and much of everything else transited through Islamic lands by Arab traders. After about 1000, European vessels from the Republic of Venice and other rising small sea states increasingly handled the final transshipments from Alexandria and other Arab ports throughout the Mediterranean in commercial alliances that often transcended religious rivalries.
Islam's expansive economic power made it a great military force that encroached upon and threatened neighboring civilizations. The native sub-Saharan civilizations of the Niger River fell under domination by Muslim states following the conquest of Ghana in 1076. Much of East Africa, with the notable exception of the Abyssinian highlands of modern Ethiopia, also succumbed. In India, Hindu civilization was in retreat from Islamic conquests over hundreds of years through the seventeenth century. Europe, too, barely survived the onslaught of Islam's initial military juggernaut from 632 to 718, and remained at peril for several centuries in the heated clash of civilizations that continued in earnest across the Mediterranean throughout the sixteenth century.
Christianity, and all that later flowered into Western civilization, came closest to possible extinction in the year from AD August 717 to August 718. During those 12 months, a huge Muslim naval and army force of over 2,000 ships and 200,000 men laid siege to Constantinople, seat of the Byzantine Empire, inheritor of Rome's civilization, and Christendom's greatest city. Had the imperial city, located on the strategic triangular promontory overlooking the junction of the Bosporus Strait and the Sea of Marmara that controlled the narrow 225-mile waterway linking the Mediterranean and Black Sea trade routes and divided Europe from Asia, fallen under Islam's flag, the entire Mediterranean Sea likely would have become a Muslim lake. Europe's interior, via the river Danube and toward the Rhine, would have been wide open for an easy Muslim march of conquest. Europe, and the entire Western world, today might be Muslim. In the event, the siege of Constantinople would be an epic turning point in the clash of civilizations between Islam and the West. It was also a dramatic illustration of the geostrategic advantage of a strong water defense.
In the early eighth century, the Christian world outside Constantinople was sparsely scattered and doctrinally divided among Greek, Latin, Syriac, and Coptic churches. Rome, laid waste by multiple sackings and its aqueduct water supply system in ruins, was a shrunken shadow of its former self and under Byzantine protection. Latin Church missionaries were struggling to convert the barbarian European princes who ruled in the power vacuum left behind by the fallen Roman Empire. The conquests of Charlemagne and his crowning in 800 as the first Holy Roman Emperor still lay many decades in the future. Islam, by contrast, was still at the height of its explosive expansion following Muhammad's death.
The only serious setback experienced by the Arab conquerors in the seventh century had been their previous failure in 674679 to conquer Constantinople. Their overland attack had faltered when the Saharan camel proved unable to tolerate the cold of the Anatolian highlands of Turkey. Their sea attack had hinged on the success of its large siege engines and catapults against Constantinople's double walls. It, too, failed when the Byzantines counterattacked by unleashing their terrifying, newly invented, secret chemical sea-warfare weapon-"Greek fire"-upon Arab ships. The chief characteristic of Greek fire was that it combusted spontaneously and fiercely upon contact with air and was inextinguishable even in water. The secret of its precise composition was lost during the Middle Ages and remains unknown today. It was a crude oil-based substance traditionally laced with sulfur, evergreen tree pitch or quicklime; by adding the right amount of saltpeter, the mixture became ferociously self-igniting. Only sand, vinegar, and urine were believed to dampen its smoky flames. Greek fire was usually blown by an air pump through long, bronze-lined tubes toward enemy ships, where it burst into flames; alternatively, it was catapulted at attacking ships in clay jars or fired in a hail of arrows that had been saturated in it. So many of the wooden hulls of the caliph's vessels were set ablaze and so much terror inflicted upon Arab sailors by this unnerving weapon that in 679 the Muslims withdrew, and even agreed to pay an annual tribute to Constantinople. Greek fire not only saved the Byzantines, but its secret gave them a long-lasting military advantage in sea warfare that endured for a long time.
Yet the hard experience of 674679 also meant that when the Arabs returned in 717 for their revenge assault, they came better prepared and in much greater force. Once again Constantinople's defense hinged upon its supreme strategic location and sea power. The city's position made it at once easily supplied through either of the two long, narrow straits-to the east by the Bosporus, 18 miles long and less than half a mile wide in some places, or by the 40-mile-long and one-to five-mile-wide Dardanelles on the west-connecting the Black and Mediterranean seas. On the northeast side of Constantinople's peninsula, abutting the entrance to the Bosporus, was a wonderful, deep, five-mile-long harbor, the Golden Horn, which offered the only well-sheltered port in a turbulent stretch of sea. These natural geographical defensive advantages were reinforced by a great, half-mile-long chain across the harbor's mouth that the Byzantines could raise to block the entrance. The city's peninsular location meant that major fortification of walls and moat was needed only on its landward side. Its single defensive flaw was that it had only one good stream flowing into the Golden Horn to provide freshwater. To mitigate this vulnerability, Byzantine Roman water engineers had borrowed on the waterworks expertise of mother city Rome to build dams, a long-distance aqueduct, and giant underground cisterns within its walls to supply enough freshwater to withstand a siege.
The site, occupied since 658 BC by the prosperous Greek trading city of Byzantium, had been chosen, and renamed, by the Roman emperor Constantine I to replace beleaguered Rome as capital of the Roman Empire for its commanding strategic defensive and trading positions on the Black Sea. This "New Rome"-like the original it had seven hills, a bread dole for the poor, and a new Senate to entice the nobility to emigrate-was founded on AD May 11, 330. Moving to Constantinople had been one of Constantine's two historic decisions. The second, inspired by his vision of a heavenly cross heralding his power-consolidating victory in the battle of the Milvean Bridge (AD 312) on the Tiber on the outskirts of Rome, was to adopt Christianity as the favored religion of the Roman Empire. In the life-and-death struggle against Islam (717718), the fate of Constantine's second great decision depended much on the strategic foresight of his first.
The fortunes of Constantinople and Christianity were improved in their hour of crisis by the seizure of the imperial throne a few months earlier by a gifted general, crowned as Emperor Leo III. The Muslim military strategy was to assault the city's double walls from the landward side with a massive army, while two fleets bottled up the Dardanelles and the Bosporus to deny any supply relief from Mediterranean or Black Sea ports. The initial land attack, however, failed. So the Muslims settled in for a long siege to be waged, as in the late 670s, primarily on the water. This time they succeeded in sealing up the Dardanelles. The Bosporus proved more difficult. When the Muslim fleet approached Constantinople, its lead ships got caught up in swift, unfamiliar currents; Leo III promptly lowered the chain across the Golden Horn and struck the disoriented Muslim ships with Greek fire, destroying and capturing many of them.
Nature then assaulted the Muslim besiegers in their outdoor tents with an abnormally bitter winter. Their resupply was delayed. Famine and disease entered the camps, compelling the besiegers to eat their animals and even dead men's flesh. As so often is the case in the history of warfare, noncombat causes claimed more lives than enemy weapons. The besiegers suffered the added indignity of having to dump many of their dead into the sea because snow froze the ground for many weeks to prevent burial.
When the warmth returned in the spring of 718, the Muslims' luck turned. Reinforcements of 400 ships and 50,000 men arrived from Egypt. One night they succeeded in sneaking past the Golden Horn to complete the blockade that would doom the city and the Byzantine Empire. However, many of the Arabs' Coptic Christian crew chose that moment to abandon their ships and desert to the Byzantines. Informed by their gift of priceless military intelligence, Leo III in June mustered a surprise counterattack with Greek fire that routed the blockading fleet. As Coptic Christian desertions mounted, Leo followed up with an unexpected land attack on the Asian side of the waterway. Caught off guard, thousands of Muslims were slaughtered. When, at Leo's connivance, the neighboring Bulgars began to attack the Muslim forces, and rumors flew that the Frankish army was en route to join in, the caliph lifted the siege on August 15, 718, and retreated. By all accounts only 30,000 of the 210,000-man Islamic force, and only five out of its over 2,000 ships made it back home.
Constantinople was saved. That the city's impregnability endured for another 500 years alongside a far wealthier and more vibrant Islamic civilization was testimony to the disproportionate military advantages of sea power and control of geostrategically important waterways. The city was finally sacked and effectively subjugated only in 1204-not by Muslims, but by fellow Christians diverted from their intended march to the Holy Land on the Fourth Crusade by the intrigues of the mercantile-minded sea power Venice and its redoubtable, blind, octogenarian doge, Enrico Dandolo. Venice thereafter exercised commercial hegemony over the straits, controlling the lucrative routes to the Black Sea. Constantinople finally fell to the Islamic Turks only in 1453.
The enormous consequences of Constantinople's victory in 718 rippled through history for centuries. The first major effect was the survival of Christian Europe as a significant cultural and geographic rival to Islam. In 732 an expeditionary Muslim force from Spain was defeated by Frankish leader Charles Martel, grandfather of Charlemagne, on a battlefield near Poitiers, France, in what would later be regarded by Christian historians as heralding the turning point in ending the Arab Muslim land expansion in Europe. By 1097, Christian Europe was strong enough for its knights to cross the Bosporus from Constantinople and launch the successful counterattack to retake the Holy Land from Islamic control-the First Crusade.
Christian Europe's major gains against Islam were won principally through sea power. Constantinople's triumph had ensured that the eastern Mediterranean, unlike its western half, never succumbed to Islamic dominance. Between 800 and 1000, both Muslim and Christian vessels vied for supremacy over the riches of the eastern Mediterranean, plundering where possible and trading when necessary. By 1000, the city-state Republic of Venice finally gained the upper hand as the great sea power and transshipper from the central Mediterranean to the rich ports of Alexandria and the Levant. Three centuries later, Genoese merchants broke the Islamic chokehold on the Strait of Gibraltar, opening the Atlantic sea-lanes to unify the Christian Mediterranean with the emergent world of northern Europe. From about the eleventh to sixteenth centuries, Christians increasingly controlled the Mediterranean while the Muslims reigned in the Indian Ocean. Thereafter, the "Voyages of Discovery," motivated partly by the Portuguese's and other Atlantic sea powers' covetous desire to break the Italian and Muslim monopoly on trade with the East, culminated in a breakthrough all-sea route around Africa to India and momentously transformed the power relationships of world history with Europe at its center.
Islam's gradual ejection from the Mediterranean following the defeat at Constantinople not only saved Christianity. It also had far-reaching effects within Islam itself. It set off a period of upheaval and renewal that reinvigorated Arab Islam by amalgamating it with older Near Eastern civilizations to help launch what proved to be its golden age. The defeat at Constantinople signaled the end of its juggernaut military expansion, which in turn upset the internal dynamics that had held together the growing fissures within the Islamic community. Previously, victory on the battlefield had yielded ample booty and tribute from defeated populations for distribution that had smoothed over internal rivalries among Arab tribes. With diminishing bounty to share, the tribal political system of Arab privilege run by the ruling Damascus-based Ummayad caliphate also began to fuel discontent among the growing number of non-Arab Muslim converts who increasingly supplied Islam's manpower but often felt unwelcomed with second-class status.
In 750, the Ummayads were toppled in a civil war by a coalition led by a rival family descended from Muhammad's uncle, Abbas. The Abbasids' new caliphate was based on inclusion of non-Arab Muslims, governance that was comparatively professional and efficient rather than run on the basis of tribal patronage and nepotism, and religious universalism that encouraged converts with equal rights and opportunities. The new caliphate's heartland was the productive, irrigated farmland of ancient Mesopotamia, where Arab conquerors had installed themselves as large landowners. The Abbasids' commercial orientation shifted toward the east and the Indian Ocean. To celebrate their rise, they founded a new city-Baghdad-strategically positioned in a place where the Tigris and Euphrates rivers flowed near one another. This location gave the city convenient access to abundant irrigated food from the muddy floodplains and intersected major trade routes to Persia and the East. It was in Abbasid Baghdad that a great Islamic civilization first began to flourish. From 762 to 1258, when it was destroyed by the Mongols, Baghdad was the largest and grandest city anywhere outside China.
While Islamic civilization was not notably innovative in water engineering, in its ascendant period it vigorously applied known Middle Eastern technologies to get the most from its freshwater-scarce habitats. Water management thus played a key role in sustaining the power and splendor of the caliphate. Old waterworks were restored and new ones constructed. Muslim irrigation had its greatest success around Baghdad, where five dam-fed, cross country canals running from the Euphrates to the Tigris watered extensive, productive cropland. East of the Tigris, Abbasid engineers expanded the Nahrwan Canal that had been started by the Sassanian Persians in the second century AD. Water released from a famous masonry dam on Iran's Kur River that was rebuilt in about 960 irrigated large fields of sugar, rice, and cotton.
The diffusion of Middle Eastern water technologies and crops supported the spread of high Islamic civilization across the Muslim world. Underground qanats increased domestic water supplies, while water-lifting norias and shadoofs supplemented field irrigation across North Africa and in Spain. Low-level diversion dams were widespread in Muslim Spain and became an important acquisition of the Christian kings when they later expelled the Muslims from Spain.
Grand cities arose that competed with Abbasid Baghdad culturally and politically. Cordoba, lying inland on the river Guadalquiver, became the seat of a brilliant humanistic Islamic civilization in Spain presided over for a long period by the lone dynastic Ummayad family survivor of the Abbasid purge that followed the civil war. The river irrigated the surrounding plains and provided the means for transporting food and goods to Cordoba's marketplace. The tenth century saw the rise of a dazzling new city, Cairo, from which the Shiite Fatimids asserted their claim to the Islamic caliphate. The economic basis of Fatimid power was the fertile farmlands of the Nile and the extensive sea trade and camel routes through the Levant and Red Sea. By the early 1300s, Ibn Battutah, the renowned fourteenth-century Muslim traveler and diarist sometimes called "Islam's Marco Polo," marveled that because of its great size "in Cairo there are twelve thousand water-carriers who transport water on camels" throughout its sprawling network of streets and markets.
The grand Muslim cities like Cordoba, Cairo, Baghdad, and Granada, situated in hot, dry lands, displayed Muslim splendor and power by building sumptuous palaces, surrounded by shaded gardens with fountains and running water suggestive of paradise, and public baths as in ancient Rome. Wherever practicable in Islam's stream-poor landscape, Muslim engineers exploited waterpower to grind flour in traditional mills as well as to produce new products and goods. Floating water mills operated day and night on the Tigris River to produce Baghdad's daily bread while at the port city of Basra in southern Mesopotamia tidal-flow-powered mills did the same. At Basra water-powered mills also processed sugarcane, first crushing the cane and extracting its juice, which was then boiled down to produce refined, crystalline sugar. Other waterwheels powered big trip-hammers used by fullers to prepare woolen cloth and to pound vegetable fibers in water until it formed a pulp from which paper could be manufactured.
Paper production methods had come to the Islamic world serendipitously through the capture of Chinese prisoners skilled in papermaking during the victorious 751 battle of the Talas River in central Asia. These prisoners set up a workshop in Samarkand. From there papermaking technology later was transferred to Baghdad. In China the bark of the mulberry tree had long been used as the basic raw material. Lacking mulberries, rags, especially linen, were substituted in the Islamic world. The original manual production process was in two steps, with water playing a key role in both. First, torn-up rags were soaked, shredded, and beaten in vats with spiked clubs to produce a pulp-a manual process subsequently automated by pulp beaters powered by water. Next, the pulp was put in a vat of warm water, stirred, and strained through a molded wire latticework to produce rectangular sheets. The sheets were squeezed and hung dry, then rubbed as smooth as possible with stones, and finally immersed in a vat of gelatin and alum for stiffening. Baghdad's water-powered paper pulp mill process spread west to Spain, and from there to Christian Europe a century later.
Paper manufacturing played a catalytic role in diffusing knowledge rapidly through the wide availability of books. Baghdad, for instance, had over a hundred bookshops by 900. Books helped usher in a glorious era of humanist enlightenment in the sciences, arts, philosophy, and mathematics, along with economic prosperity, and relative tolerance and peace. Greek, Persian, and Sanskrit manuscripts systematically were translated into Arabic from the early ninth century at Baghdad's "House of Wisdom" created by Caliph al-Mamun. Ultimately, it would be through Islamic scholars centered in Cordoba-not the long-lived though decaying civilization of Constantinople and the Byzantine Empire-that Christian Europe became reacquainted with the works of Aristotle and its own classical Greek intellectual heritage. This rediscovery later flowered as the European Renaissance to help give birth to postmedieval Western civilization. Muslim scholars made many original discoveries that also migrated to Europe. Algebra, trigonometry's sine and tangent, the astrolabe and other navigational and geographical measuring instruments, the distillation of alcohol, and numerous medical treatments were among the most notable. Islamic alchemy contributed greatly to the development of the West's scientific knowledge and methods. Islamic instrument makers even were working on elaborate gear trains for water clocks to be driven by waterwheels in the same period that China was employing this technology. A distinguished tradition of thinkers, among the best known of whom were Avicenna and Averroes, influenced mainstream Western philosophical development.
Yet sometime toward the end of the twelfth century-some historians use the death of Averroes in 1198 as the benchmark date-Islam's most glorious era abruptly began to stagnate. Why the intellectual vitality and material growth suddenly drained away, and why its culture soon was eclipsed by more vigorous civilizations, remains one of the puzzling questions of history.
The most traumatic symbol of Islamic civilization's decline was the devastating Mongol sack of Baghdad on February 20, 1258. Mounted Mongol warriors, using gunpowder-fired weapons in their relentless surge of conquest across the Eurasian steppes from China to the Near East to the doorstep of central Europe, stormed the once-illustrious city to loot, burn, pillage, and slaughter. In customary Mongol fashion, hundreds of thousands of residents were massacred. The last caliph, in a calculated symbolic act of contempt, was trampled to death under the hoof of a Mongol horse. The obliteration of the Abbasid capital was completed by the destruction of many surrounding irrigation dikes and waterworks to render impossible any agricultural resurrection. It was the first time that non-Muslim invaders had been able to impose infidel rule in the Islamic heartland. Christian Europe was spared a similar agonizing fate as that experienced at the hand of the Mongols by both Islam and China only due to a fluke of history. News of the death of Genghis's son and successor, Ogadei, had reached the banks of the Elbe River during the 1241 conquests when Europe lay prone for the taking. Mongol commanders, uncertain how the power vacuum in Karakorum would be filled, voluntarily pulled back their forces into Russia. Eventually they invaded other regions, and looked beyond the relatively meager wealth of medieval Europe for richer prizes.
Yet Islamic civilization had been in critical decline long before the arrival of the vanquishing Mongol cavalry. Like the Persian and Byzantine empires overrun by the first Arab armies of the seventh century, the foundation of its economic prosperity had grown internally stagnant. A principal cause was faltering water management and its inability to keep technologically ahead of its inherent scarcity of freshwater resources. The agricultural productivity of Mesopotamia, for instance, deteriorated markedly with the rising political influence of Islam's nomadic converts who increasingly supplied the Arab caliphate's military manpower. Most notable of these were the Turks, who held effective power in Baghdad after 1055 under the nominal leadership of the Abbasids. Dependency on the Turks was a consequence of the limitation water scarcity had imposed on the size of the ruling native Arab population. While the Abbasid dynasty's founders had arduously rebuilt and maintained irrigation waterworks on the Tigris-Euphrates and Nahrwan canal system and had expanded cultivated cropland to its largest extent into the eleventh century, the recently nomadic Turks were steeped in the traditions of steppe herders who followed their sheep and horses between water holes and seasonal grasslands. Under Turkish influence, centralized political authority waned and Mesopotamia's irrigation system eroded. Inadequate maintenance caused irrigation and drainage canals to clog with silt. Soils became waterlogged and deadly salt rose to the surface of the floodplains between the twin rivers. As in ancient times, salt-whitened fields produced falling agricultural yields and declining population levels.
Deteriorating irrigation maintenance also helped cause both the Euphrates and the Tigris to make major disruptive course shifts around the year 1200. The Tigris's return to its former, more easterly channel north of Baghdad was a twin disaster because not only did this realignment dry up a large tract of irrigated cropland, but it also destroyed part of the 400-foot-wide Nahrwan transport and irrigation canal and the agricultural network it supported downstream. The agricultural decline in Mesopotamia coincided with a parallel shrinkage and collapse by the twelfth century of irrigation in Egypt. Thus both of the Islamic world's great breadbaskets fell into crisis at the same time. As always, the level of Nile floods was the key determinant of Egyptian prosperity and the political system that depended upon it. Ample Nile floods had buttressed the first three centuries of Arab rule. A period of low Nile floods between 945 and 977, however, eroded the amount of land under cultivation and paved the way for the conquest of Egypt by the Shiite Fatimids in 969. Fatimid rule was eventually undermined by two generations of low Nile floods that produced cannibalism, plague, and decaying waterworks. In 1200 one-third of Cairo's population perished from severe famine when disastrous low floods returned after a long period of normality. This catastrophe fueled the enduring Egyptian suspicion that the upriver emperors of Ethiopia somehow had made good on their threat to divert the Nile's waters. By the time the Mamluks, white Muslim slave soldiers of ethnic Turkish origins, seized power in Egypt in 1252, irrigated agriculture had fallen into such desuetude that the Nile breadbasket was able to support no greater population than the one Arab conquerors had inherited from the Byzantines in the seventh century. The revival of Nile irrigation awaited the water engineering projects of the Turkish and British overlords in the nineteenth and twentieth centuries.
In Muslim Spain the problem was less one of waterworks deterioration than of a failure to innovate to find more efficient ways to exploit their existing water resources. When the Christian Europeans reconquered Spain, they inherited an extensive irrigation network with highly developed social and administrative processes-including the famous water court at Valencia, the oldest democratic institution in Europe, whose elected judges have adjudicated irrigation disputes in public for over a millennium. But it was entirely based on Middle Eastern traditions of small-scale river diversion dams for irrigation, water-power, and water supply. Muslim engineers had ample familiarity with large impoundment dams and aqueducts used in Spain by the ancient Romans. But they never experimented with them in order to improve their water use productivity. Their Christian successors did. Their successful innovations helped Spain flourish after 1492 when the armies of King Ferdinand and Queen Isabella expelled the last Moors from the Iberian Peninsula.
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