Founded in 762, Baghdad was for five centuries the heart of the Islamic world: capital of the Abbasid Caliphate, city of the House of Wisdom, centre of law, medicine, mathematics and poetry. By the mid-13th century, however, the city's political power had long waned, and the caliphate had become a largely symbolic institution.

Hulagu, a grandson of Genghis Khan, led the great Mongol army advancing westward. When the last Abbasid caliph, al-Musta'sim, refused his demand to surrender, Hulagu besieged Baghdad in early 1258. Within a few weeks the walls were breached; the city was sacked and burned for days. According to the sources, hundreds of thousands were killed. The caliph was executed — by tradition, to avoid the ill omen of spilling royal blood, rolled in a carpet and trampled under horses.

The city's libraries were burned or thrown into the Tigris; legend says the river ran black with ink for days. Exaggerated though it may be, that image symbolises the destruction of a civilisation's memory. The fall of Baghdad is regarded as the symbolic end of the centuries-long Islamic golden age.

The Mongol advance was halted two years later by the Mamluks at Ain Jalut in Palestine; but Baghdad never regained its old central role. The centre of gravity of the Islamic world shifted to other cities — Cairo, Konya, and later Istanbul.