of the Church of the East. The Sassanid Persians under Ardashir I destroyed the Parthian Empire and conquered the region in 224 AD. The region was thus a province of the Persian Empire for four centuries, until the Muslim conquest of Persia in the 7th century, although a number of indigenous states evolved during the Parthian era, such as Adiabene, Osroene and Hatra.
Abbasid Empire
The Islamic conquest in the 7th century established Islam in Iraq. Under the Rashidun Caliphate, the prophet Muhammad's cousin and son-in-law Ali moved his capital to Kufa "fi al-Iraq" when he became the fourth caliph. The Umayyad Caliphate ruled the province of Iraq from Damascus in the 7th century. (However, eventually there was a separate, independent Caliphate of Córdoba.)
The Abbasid Caliphate built the city of Baghdad in the 8th century as their capital, and it became the leading metropolis of the Arab and Muslim world for five centuries. Baghdad was the largest multicultural city of the Middle Ages, peaking at a population of more than a million, and was the centre of learning during the Islamic Golden Age. The Mongols destroyed the city during the siege of Baghdad in the 13th century.
Mongol invasions
In 1257, Hulagu Khan amassed an unusually large army, a significant portion of the Mongol Empire's forces, for the purpose of conquering Baghdad. When they arrived at the Islamic capital, Hulagu Khan demanded surrender but the last Abbasid Caliph Al-Musta'sim refused. This angered Hulagu, and, consistent with Mongol strategy of discouraging resistance, Baghdad was decimated. Estimates of the number of dead range from 200,000 to a million.
The Mongols destroyed the Abbasid Caliphate and The Grand Library of Baghdad (Arabic بيت الحكمة Bayt al-Hikma, lit., House of Wisdom), which contained countless precious and historical documents. The city has never regained its status as major center of culture and influence. Some
