Abbasid Caliphate

• 1. Introduction

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  The Abbasid Caliphate began not with a coronation but with a revolt carried out under the sign of the Black Standard, launched from the distant eastern region of Khurasan on the 9th of June 747. Within three years, the rebels had shattered the Umayyad dynasty and placed their own man, Abu al-Abbas al-Saffah, on the throne as the first caliph of a new Islamic empire. For the next five centuries, the Abbasids would rule from Iraq, building a capital in Baghdad that became the intellectual center of the medieval world. How did a family descended from Muhammad's uncle turn a provincial uprising into a dynasty that lasted longer than the Roman Empire at its height? What made Baghdad the city that scholars, scientists, and poets called the greatest on earth? And how did an empire that stretched from Spain to Central Asia finally fall to a grandson of Genghis Khan who had al-Musta'sim, the last reigning caliph, wrapped in a carpet and trampled to death by horses?

• 2. The Revolution from the East

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  Abu Muslim rose from Khurasan in 747, commanding close to ten thousand soldiers when hostilities formally began in the city of Merv. The Abbasids drew their legitimacy from a specific family claim: their ancestor Abbas ibn Abd al-Muttalib was one of the youngest uncles of Muhammad, placing them within the same Banu Hashim clan. This mattered enormously in a political world where the ruling Umayyads, who had reigned since 661, did not share that lineage. The Umayyads had suppressed multiple attempts to bring other members of Muhammad's family to power, and the Abbasids made those grievances central to their campaign.

  They also appealed directly to the mawali, non-Arab Muslims who were treated as a lower class within the Umayyad system despite having converted to Islam. According to the historian Ira Lapidus, the revolt was supported largely by Arabs, mainly the aggrieved settlers of Merv, alongside the Yemeni faction and their mawali. That coalition gave the movement a breadth the Umayyads could not easily dismiss.

  General Qahtaba pursued the fleeing Umayyad governor Nasr ibn Sayyar westward, winning the Battle of Gorgan, the Battle of Nahavand, and the Battle of Karbala all in the year 748. The rebellion's first leader, Ibrahim al-Imam, was captured and died in prison that year, but his brother Abdallah took up the cause. At a battle near the Great Zab river in 750, the Abbasids defeated the Umayyad caliph Marwan II, who fled to Egypt and was killed there. Nearly all remaining members of the Umayyad family were eliminated, though one prince named Abd ar-Rahman escaped and founded the Umayyad Emirate of Cordoba in present-day Spain in 756.

• 3. Building Baghdad

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  In 762, after years of ruling from provisional capitals, the caliph al-Mansur made a decisive choice. He founded a new city on the Tigris River near the ruins of the ancient Persian capital Ctesiphon, officially naming it Madinat al-Salam, the City of Peace. The world would come to know it as Baghdad. Its layout was strikingly deliberate: a circular plan surrounded by massive brick walls constructed in successive rings by a workforce of one hundred thousand, with four great gates named Kufa, Basra, Khurasan, and Syria. At the center stood al-Mansur's palace, covering 360,000 square feet, alongside a great mosque of ninety thousand square feet.

  The city grew at a pace that astonished contemporaries. Under Harun al-Rashid, bookstores proliferated throughout Baghdad after paper arrived to replace parchment. Chinese papermakers had been among those taken prisoner at the Battle of Talas in 751, and as prisoners of war they were sent to Samarkand, where they helped establish the first Arab paper mill. In 794, Jafar al-Barmak built the first paper mill within Baghdad itself. Al-Rashid later required that government dealings be conducted on paper rather than parchment, on the practical ground that records written in ink could not easily be altered. Eventually, an entire street in Baghdad's commercial district was given over to the sale of paper and books.

  Al-Mansur also established the House of Wisdom in Baghdad, where Muslim and non-Muslim scholars gathered to translate and collect the world's knowledge into Arabic. Works from Greek, Persian, Indian, Roman, Chinese, Egyptian, and North African traditions flowed through this institution. Many texts that would otherwise have been lost were preserved in Arabic and later passed into Turkish, Hebrew, and Latin. The caliphate's scientists, according to the scholar Huff, were in the forefront of advance in virtually every field, from astronomy and mathematics to medicine and optics.

• 4. Harun al-Rashid and His Court

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  Harun al-Rashid's reign is traditionally held to mark the height of Abbasid power and prestige. His father al-Mahdi had restarted the wars with the Byzantine Empire, and al-Rashid pushed those campaigns hard. His navy seized Cyprus, and in 806 he personally led a massive invasion that culminated in a victory at the Battle of Krasos. He also maintained embassies at the Tang Chinese court, a relationship recorded in the Old Book of Tang, the most notable delegations being those of al-Saffah, al-Mansur, and al-Rashid himself.

  The internal architecture of the caliphate changed significantly during this period. The position of vizier, originally little more than a secretarial role, expanded into a powerful executive office under the Barmakids, an Iranian family close to the Abbasids. For many years al-Rashid delegated state affairs to them, which gave the caliphate a more ceremonial character than it had held under the Umayyads. Then in 803, without warning, al-Rashid turned against the Barmakids, imprisoning or killing most of them. Contemporary writers and later historians have never fully explained the reasons behind this sudden reversal.

  Al-Rashid's most consequential decision was his succession plan, established in 802. He decreed that his son al-Amin would become caliph and control Iraq and the western empire, while his other son al-Ma'mun would rule Khurasan and most of the east. After al-Rashid died in 809 while managing a rebellion in Khurasan, the pact collapsed. Civil war broke out between the two brothers. When al-Ma'mun's forces besieged Baghdad and the city fell in 813, al-Amin was captured and executed on the orders of al-Ma'mun's general Tahir ibn Husayn. It was the first time an Abbasid ruler had been publicly executed, and it left a permanent mark on the caliphate's standing.

• 5. Science, Paper, and the Golden Age

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  Muhammad ibn Musa al-Khwarizmi produced his landmark text Kitab al-Jabr wa-l-Muqabala during the Abbasid era, and the word algebra is derived directly from its title. He is regarded by some as the father of algebra, and the terms algorism and algorithm both trace back to his name. He also played a central role in spreading the Arabic numerals and the Hindu-Arabic numeral system beyond the Indian subcontinent.

  In 1021, Ibn al-Haytham published his Book of Optics, which developed what scholars have identified as an early scientific method. His empirical proof that light rays enter the eyes rather than being emitted by them stood as a landmark in the history of optics. He has been described as the world's first true scientist, an assessment rooted in his systematic use of experiments to distinguish between competing theories. During the 9th century, Baghdad housed over eight hundred doctors, and the clinical distinction between measles and smallpox was established during this period.

  Avicenna, the Persian scholar known in the West as Ibn Sina, produced The Canon of Medicine and The Book of Healing, encyclopedic works that directly shaped European science during the Renaissance. Al-Battani improved the precision of measurements of the precession of the Earth's axis, and his corrections to the geocentric model were later incorporated into the Copernican heliocentric system. The caliphate's engineers also developed industrial uses of waterpower, crankshafts, gears, and dams that allowed tasks once done by hand to be mechanized, a transformation scholars have compared to the later arrival of the printing press in Europe.

  Paper itself was one of the caliphate's most far-reaching exports. Easier to manufacture than parchment and better at absorbing ink than papyrus, paper spread from the caliphate's mills into al-Andalus and then into the rest of Europe in the 10th century. Islamic paper makers developed assembly-line methods of hand-copying manuscripts, producing editions on a scale that Europe would not match for centuries.

• 6. Fracture and the Puppet Caliphs

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  Following the civil war between al-Amin and al-Ma'mun, the caliphs recognized that their traditional Khurasani soldiers could no longer be relied upon. Al-Ma'mun began recruiting soldiers from new sources, and his brother and successor al-Mu'tasim accelerated the process. The most important new troops were Turkic people from Central Asia, referred to in Arabic chronicles as "Turks." Many were originally purchased or captured slaves who were paid regular salaries and likely freed; their loyalty ran to the caliph alone because they had no political ties to the existing elites.

  The influx of these soldiers into Baghdad created tensions with the city's population and with the older political class. In 836, al-Mu'tasim founded a brand-new capital called Samarra on an open site north of Baghdad, large enough to house the army and accommodate the construction of massive palaces. The city was developed over sixty years, complete with racecourses and game preserves. The move did not stabilize the caliphate. In 861, the caliph al-Mutawakkil was murdered at a party by a group of Turkish soldiers, the first time the Abbasid military intervened so directly and violently at court. The period that followed, sometimes called the Anarchy at Samarra, saw four different caliphs come and go between 861 and 870, each at the mercy of military factions. In 865, Turkish soldiers from Samarra besieged Baghdad itself to depose the caliph al-Musta'in.

  By the 10th century, the caliphs had become figureheads. Real power over Baghdad passed to the Iranian Buyids in 945, then to the Seljuq Turks in 1055. The Buyid bureaucrat Hilal al-Sabi described a court at Baghdad that was still highly ritualized even as the Buyids held effective control. When the Seljuq sultan Toghril Beg finally drove out a rebel who had raised the Shia Fatimid banner in Baghdad in 1056-1057, the caliph remained the nominal head of the Islamic community but could not match the military strength of the men who actually governed the empire.

• 7. The Mongol Sack of Baghdad

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  In 1252, Hulagu Khan, a grandson of Genghis Khan and brother of the ruling Mongol ruler Mongke Khan, was placed in charge of a western campaign. By 1257 he had destroyed the Assassins in Iran and then wrote to the Abbasid caliph al-Musta'sim demanding submission. The caliph refused. Months of diplomacy followed, during which al-Musta'sim's vizier Ibn al-Alqami, a Shia, was later accused of corresponding with the Mongols and informing them of Baghdad's weaknesses, though this charge has remained contested.

  The Mongols began their siege on the 29th of January 1258. On the 10th of February, al-Musta'sim agreed to meet Hulagu, who demanded that the caliph order his defenders to lay down arms and come out of the city in exchange for mercy. The caliph complied. The Mongols then slaughtered the population and began sacking the city on the 13th of February. Contemporary accounts record destruction, looting, rape, and killing on a massive scale over many days, with hundreds of thousands killed and the city reduced to near-empty ruins. Some communities were spared, including Christians and Shias.

  The Mongols feared a supernatural disaster if the blood of al-Musta'sim, a direct descendant of Muhammad's uncle and the head of a dynasty that had reigned for five centuries, was spilled on the ground. Following a Mongol taboo against shedding royal blood, Hulagu had the caliph wrapped in a carpet and trampled to death by horses on the 20th of February 1258. The caliph's immediate family was also executed. His youngest son was sent to Mongolia; a daughter became a slave in Hulagu's harem. The fall of Baghdad is traditionally regarded as marking the end of the classical, or golden, age of Islamic civilization, and it reshaped the geopolitics of the entire Middle East, leaving Iraq, Iran, and most of the eastern lands under Mongol control.

• 8. The Caliphate in Exile

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  A surviving member of the Abbasid family was invited to Cairo in 1260-1261 by the Mamluk ruler Baybars, who needed political legitimacy for his newly established sultanate. The new caliph, al-Mustansir II, was a brother of the last reigning caliph al-Mustansir. In 1262 he disappeared while leading a small army in an attempt to retake Baghdad from the Mongols. Baybars replaced him with al-Hakim I, who had just been proclaimed in Aleppo.

  The Abbasid caliphs in Cairo continued as a ceremonial institution within the Mamluk Sultanate, one that carried significant prestige without political power. Rulers from across the Muslim world sought their endorsement well into the 14th century: the sultans of Delhi, the Muzaffarid sultan Muhammad, the Jalayirid sultan Ahmad, and the Ottoman sultan Bayezid I all sought investiture diplomas or declared nominal allegiance to the Cairo caliph. Caliph al-Musta'in even held the sultanate itself for six months in 1412.

  The institution faded during the 15th century. When the Ottoman sultan Selim I defeated the Mamluks in 1516 and conquered Egypt in 1517, the last Abbasid caliph, al-Mutawakkil III, was brought to the Ottoman capital of Constantinople. The claim that al-Mutawakkil III formally transferred the caliphate to the Ottoman sultan during their meeting in Aleppo in 1516 is a legend elaborated in the 19th century; contemporary accounts do not support it. The Ottomans themselves did not use the title of caliph before the mid-16th century and only invoked it vaguely and inconsistently after that. The dynasty that had launched a revolution under the Black Standard in 747, built Baghdad from a blank site into the intellectual capital of the medieval world, and survived in ceremonial form for three centuries after Hulagu's horsemen trampled its last ruling caliph, passed at last into historical obscurity.