The Mongols sacked Baghdad in 1258 and destroyed its great library

Hulagu Khan's Mongol army took Baghdad after a twelve-day siege in 1258, killing much of the population and demolishing the House of Wisdom, a center of scholarship that had gathered manuscripts for five centuries. Chroniclers claimed so many books were dumped into the Tigris that the river ran black with ink, a detail historians treat as legend, though the destruction itself is well documented. The sack effectively ended the Abbasid Caliphate and the Islamic Golden Age.

— Hulagu Khan, Mongol Empire, Siege of Baghdad (1258) — 1258 CE