In the late 11th century, the Khwarazmian dynasty assumed control over Iraq. This period of Turkic secular rule and the Abbasid caliphate concluded with the Mongol invasions in the 13th century.^[51] The Mongols, led by Genghis Khan, had conquered Khwarezmia by 1221. However, Iraq experienced a temporary reprieve due to Genghis Khan's death in 1227 and subsequent power struggles within the Mongol Empire. Möngke Khan, from 1251, reignited Mongol expansion, and when Caliph al-Mustasim refused Mongol demands, Baghdad faced a siege led by Hulagu Khan in 1258.

The Siege of Baghdad, a crucial event in the Mongol conquests, spanned 13 days from 29 January to 10 February 1258. The Ilkhanate Mongol forces, along with their allies, besieged, captured, and ultimately sacked Baghdad, the Abbasid Caliphate's capital at the time. This siege resulted in the massacre of most of the city's inhabitants, potentially numbering in the hundreds of thousands. The extent of the destruction of the city's libraries and their valuable contents remains a topic of debate among historians. The Mongol forces executed Al-Musta'sim and inflicted severe depopulation and devastation on Baghdad. This siege symbolically marked the end of the Islamic Golden Age, a period during which the caliphs had extended their dominion from the Iberian Peninsula to Sindh.