Abbasid Revolution (750–751)
The Abbasid caliphs were Arabs descended from Abbas ibn Abd al-Muttalib, one of the youngest uncles of Muhammad and of the same Banu Hashim clan. The Abbasids claimed to be the true successors of Prophet Muhammad in replacing the Umayyad descendants of Banu Umayya by virtue of their closer bloodline to Muhammad.
The Abbasids also distinguished themselves from the Umayyads by attacking their moral character and administration in general. According to Ira Lapidus, "The Abbasid revolt was supported largely by Arabs, mainly the aggrieved settlers of Merv with the addition of the Yemeni faction and their Mawali". The Abbasids also appealed to non-Arab Muslims, known as mawali, who remained outside the kinship-based society of the Arabs and were perceived as a lower class within the Umayyad empire. Muhammad ibn 'Ali, a great-grandson of Abbas, began to campaign for the return of power to the family of Prophet Muhammad, the Hashimites, in Persia during the reign of Umar II.
During the reign of Marwan II, this opposition culminated in the rebellion of Ibrahim the Imam, the fourth in descent from Abbas. Supported by the province of Khorasan, Persia, even though the governor opposed them, and the Shi'i Arabs, he achieved considerable success, but was captured in the year 747 and died, possibly assassinated, in prison.
On 9 June 747 (15 Ramadan AH 129), Abu Muslim, rising from Khorasan, successfully initiated an open revolt against Umayyad rule, which was carried out under the sign of the Black Standard. Close to 10,000 soldiers were under Abu Muslim's command when the hostilities officially began in Merv. General Qahtaba followed the fleeing governor Nasr ibn Sayyar west defeating the Umayyads at the Battle of Gorgan, the Battle of Nahāvand and finally in the Battle of Karbala, all in the year 748.
The quarrel was taken up by Ibrahim's brother Abdallah, known by the name of Abu al-'Abbas as-Saffah, who defeated the Umayyads in 750 in the battle near the Great Zab and was subsequently proclaimed caliph. After this loss, Marwan fled to Egypt, where he was subsequently assassinated. The remainder of his family, barring one male, were also eliminated.
Immediately after their victory, As-Saffah sent his forces to Central Asia, where his forces fought against Tang expansion during the Battle of Talas. The noble Iranian family Barmakids, who were instrumental in building Baghdad, introduced the world's first recorded paper mill in the city, thus beginning a new era of intellectual rebirth in the Abbasid domain. As-Saffah focused on putting down numerous rebellions in Syria and Mesopotamia. The Byzantines conducted raids during these early distractions.
The city of Baghdad
between 767 and 912 AD. The round plan reflects pre-Islamic Persian urban design.
The first change the Abbasids, under Al-Mansur, made was to move the empire's capital from Damascus, in Syria, to Baghdad in Iraq. This was to both appease as well to be closer to the Persian mawali support base that existed in this region more influenced by Persian history and culture, and part of the Persian mawali demand for less Arab dominance in the empire. Baghdad was established on the Tigris River in 762. A new position, that of the vizier, was also established to delegate central authority, and even greater authority was delegated to local emirs.
This eventually meant that many Abbasid caliphs were relegated to a more ceremonial role than under the Umayyads, as the viziers began to exert greater influence, and the role of the old Arab aristocracy was slowly replaced by a Persian bureaucracy. During Al-Mansur's time control of Al-Andalus was lost, and the Shiites revolted and were defeated a year later at the Battle of Bakhamra.
The Abbasids had depended heavily on the support of Persians in their overthrow of the Umayyads. Abu al-'Abbas' successor, Al-Mansur welcomed non-Arab Muslims to his court. While this helped integrate Arab and Persian cultures, it alienated many of their Arab supporters, particularly the Khorasanian Arabs who had supported them in their battles against the Umayyads.
These fissures in their support led to immediate problems. The Umayyads, while out of power, were not destroyed. The only surviving member of the Umayyad royal family, which had been all but annihilated, ultimately made his way to Spain where he established himself as an independent Emir (Abd ar-Rahman I, 756). In 929, Abd ar-Rahman III assumed the title of Caliph, establishing Al Andalus from Córdoba as a rival to Baghdad as the legitimate capital of the Islamic Empire.
In 756, the Abbasid Caliph Al-Mansur sent over 4,000 Arab mercenaries to assist the Chinese Tang dynasty in the An Shi Rebellion against An Lushan. The Abbasides or "Black Flags," as they were commonly called, were known in Tang dynasty chronicles as the hēiyī Dàshí, "The Black-robed Tazi", (黑衣大食) ("Tazi" being a borrowing from Persian Tāzī, the word for "Arab").[nb 1][nb 2][nb 3][nb 4][nb 5] Al-Rashid sent embassies to the Chinese Tang dynasty and established good relations with them.[nb 6][nb 7] After the war, these embassies remained in China  with Caliph Harun al-Rashid establishing an alliance with China. Several embassies from the Abbasid Caliphs to the Chinese court have been recorded in the T'ang Annals, the most important of these being those of Abul Abbas al-Saffah, the founder of the Abbasid dynasty, Abu Jafar and Harun al-Rashid.
Abbasid Golden Age (775–861)
receiving a delegation sent by Charlemagne
at his court in Baghdad. Painting by German painter
Julius Köckert (1827–1918), dated 1864. Oil on canvas.
The Abbasid leadership had to work hard in the last half of the 8th century (750–800), under several competent caliphs and their viziers to overcome the political challenges created by the far flung nature of the empire, and the limited communication across it and usher in the administrative changes needed to keep order. It was also during this early period of the dynasty, in particular during the governance of al-Mansur, Harun al-Rashid, and al-Ma'mun, that the reputation and power of the dynasty was created.
Al-Mahdi restarted the fighting with the Byzantines and his sons continued the conflict until Empress Irene pushed for peace. After several years of peace, Nikephoros I broke the treaty, then fended off multiple incursions during the first decade of the 9th century. These attacks pushed into the Taurus Mountains culminating with a victory at the Battle of Krasos and the massive invasion of 806, led by Rashid himself.
Rashid's navy also proved successful as he took Cyprus. Eventually, the momentum turned and much of the land gained was lost. Rashid decided to focus on the rebellion of Rafi ibn al-Layth in Khorasan and died while there. While the Byzantine Empire was fighting Abbasid rule in Syria and Anatolia, military operations during this period were minimal, as the caliphate focused on internal matters, its governors exerting greater autonomy and using their increasing power to make their positions hereditary.
At the same time, the Abbasids faced challenges closer to home. Harun al-Rashid turned on the Barmakids, a Persian family that had grown significantly in power within the administration of the state and killed most of the family. During the same period, several factions began either to leave the empire for other lands or to take control of distant parts of the empire away from the Abbasids. The reign of al-Rashid and his sons were considered to be the apex of the Abbasids.
After Rashid's death, the empire was split by a civil war between the caliph al-Amin and his brother al-Ma'mun who had the support of Khorasan. This war ended with a two-year siege of Baghdad and the eventual death of al-Amin in 813. Al-Ma'mun ruled for 20 years of relative calm interspersed with a rebellion supported by the Byzantines in Azerbaijan by the Khurramites. Al-Ma'mun was also responsible for the creation of an autonomous Khorasan, and the continued repulsing of Byzantine forays.
Al-Mu'tasim gained power in 833 and his rule marked the end of the strong caliphs. He strengthened his personal army with Turkish mercenaries and promptly restarted the war with the Byzantines. His military excursions were generally successful culminating with a resounding victory in the Sack of Amorium. His attempt at seizing Constantinople failed when his fleet was destroyed by a storm. The Byzantines restarted the fighting by sacking Damietta in Egypt. Al-Mutawakkil responded by sending his troops into Anatolia again, sacking and marauding until they were eventually annihilated in 863.