the Abbasid Empire (744 to 1517)
Abbasid is the dynastic name generally given to the caliph of Baghdad, the second of the two great Sunni Muslim caliphates (the first being the Rashidun Caliphate) of the Arab Empire, that overthrew the Umayyad caliphs from all but Spain. It was built by the descendant of Muhammad's youngest uncle, Abbas ibn Abd al-Muttalib. It seized power in 750 CE and shifted the capital from Damascus to Baghdad. It flourished for two centuries,


Rise:
The Abbasid caliphs officially based their claim to the caliphate on their descent from Abbas ibn Abd al-Muttalib (AD 566 � 662), one of the youngest uncles of Muhammad, by virtue of which descent they regarded themselves as the rightful heirs of Muhammad as opposed to the Umayyads. The Umayyads were descended from Umayya, and were a clan separate from Muhammad's in the Quraish tribe.
The Abbasids also distinguished themselves from the Umayyads by attacking their secularism, moral character, and administration in general. The Abbasids also appealed to non-Arab Muslims, known as mawali, who remained outside the kinship-based society of Arab culture and were perceived of 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 Muhammad, the Hashimites, in Persia during the reign of Umar II, Muhammad ibn Ali.
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, he achieved considerable successes, but was captured (AD 747) and died in prison � as some hold, assassinated. The quarrel was taken up by his brother Abdallah, known by the name of Abu al-'Abbas as-Saffah, who, with victory on the Greater Zab River (750), defeated the Umayyads and was proclaimed Caliph.


Their rule was ended when Hulagu Khan, the Mongol conqueror, sacked Baghdad. While they continued to claim authority from their base in Egypt, the dynasty's secular authority had ended. Descendants of the Abbasids include the al-Abbasi tribe who live northeast of Tikrit in modern-day Iraq.


Science under the Abbasids:
A number of medieval thinkers and scientists living under Islamic rule played a role in transmitting Islamic science to the Christian West. They contributed to making Aristotle known in Christian Europe. In addition, the period saw the recovery of much of the Alexandrian mathematical, geometric, and astronomical knowledge, such as that of Euclides and Claudius Ptolemy. These recovered mathematical methods were later enhanced and developed by other Islamic scholars, notably by Al-Biruni, and Abu Nasr Mansur.
Medicine was an area of science that advanced particularly during the Abbasids' reign. During the ninth century, Baghdad contained over 1800 doctors, and great discoveries in the understanding of anatomy and diseases were made. The clinical distinction between measles and smallpox was discovered during this time. Famous scientist Ibn Sina (known to the West as Avicenna) produced treatises and works that summarized the vast amount of knowledge that scientists had accumulated, and is often known as the father of modern medicine. The work of him and many others directly influenced the research of European scientists during the Renaissance and even later.
Three speculative thinkers, al-Kindi, al-Farabi, and Avicenna, combined Aristotelianism and Neoplatonism with other ideas introduced through Islam.

Baghdad :
Within a generation of its founding, Baghdad became a hub of learning and commerce. The House of Wisdom was an establishment dedicated to the translation of Greek, Middle Persian and Syriac works. The Barmakids were influential in bringing scholars from the nearby Academy of Gundishapur, facilitating the introduction of Greek and Indian science into the Arabic world. Baghdad was likely the largest city in the world from shortly after its foundation until the 930s, when it was tied by C?rdoba.[8] Several estimates suggest that the city contained over a 2 million inhabitants at its peak. Many of Scheherazade's tales in One Thousand and One Nights are set in Baghdad during this period.
By the 10th century, the city's population was between 2,000,000 to 2,500,000 . Baghdad's early meteoric growth slowed due to troubles within the Caliphate, including relocations of the capital to Samarra (during 808�819 and 836�892), the loss of the western and easternmost provinces, and periods of political domination by the Iranian Buwayhids (945�1055) and Seljuk Turks (1055�1135). Nevertheless, the city remained one of the cultural and commercial hubs of the Islamic world until February 10, 1258, when it was sacked by the Mongols under Hulagu Khan during the sack of Baghdad. The Mongols massacred All of the city's inhabitants, including the Abbasid Caliph Al-Musta'sim, and destroyed large sections of the city. The canals and dykes forming the city's irrigation system were also destroyed. The sack of Baghdad put an end to the Abbasid Caliphate, a blow from which the Islamic civilization never fully recovered.

At this point Baghdad was ruled by the Il-Khanids, the Mongol emperors of Iran. In 1401, Baghdad was again sacked, by Timur ("Tamerlane"). It became a provincial capital controlled by the Jalayirid (1400�1411), Qara Quyunlu (1411�1469), Aq Quyunlu (1469�1508), and Safavid (1508�1534) dynasties

Ottoman Baghdad (16th to 19th c.)
In 1534, Baghdad was conquered by the Ottoman Turks. Under the Ottomans, Baghdad fell into a period of decline, partially as a result of the enmity between its rulers and Persia. For a time, Baghdad had been the largest city in the Middle East before being overtaken by Constantinople in the 16th century. The city saw relative revival in the latter part of the 18th century under the Mamluk rule. The Nuttall Encyclopedia reports the 1907 population of Baghdad as 185,000.

During the 1970s Baghdad experienced a period of prosperity and growth because of a sharp increase in the price of petroleum, Iraq's main export. New infrastructure including modern sewage, water, and highway facilities were built during this period. However, the Iran-Iraq War of the 1980s was a difficult time for the city, as money flowed into the army and thousands of residents were killed. Iran launched a number of missile attacks against Baghdad, although they caused relatively little damage and few casualties. In 1991 the Gulf War caused damage to Baghdad's transportation, power, and sanitary infrastructure.



Abbasid Empire at its peak