The last Abbasid caliph surrendered Baghdad to the besieging Mongol army of Hulegu Khan, who later sacked the city, killing hundreds of thousands of people.

The Abbasid Caliphate or Abbasid Empire was the third caliphate to succeed the Islamic prophet Muhammad. It was founded by a dynasty descended from Muhammad's uncle, Abbas ibn Abd al-Muttalib, from whom the dynasty takes its name. After overthrowing the Umayyad Caliphate in the Abbasid Revolution of 750 CE (132 AH), they ruled as caliphs based in modern-day Iraq, with Baghdad being their capital for most of their history.

The siege of Baghdad took place in early 1258. A large army commanded by Hulegu, a prince of the Mongol Empire, attacked the historic capital of the Abbasid Caliphate after a series of provocations from its ruler, caliph al-Musta'sim. Within a few weeks, Baghdad fell and was sacked by the Mongol army—al-Musta'sim was killed alongside hundreds of thousands of his subjects. The city's fall has traditionally been seen as marking the end of the Islamic Golden Age; in reality, its ramifications are uncertain.

The Mongol Empire was the largest contiguous empire in history. Originating in present-day Mongolia in East Asia, the empire at its height stretched from the Sea of Japan to Eastern Europe, extending northward into the Arctic; east and southward into the Indian subcontinent, mounting invasions of Southeast Asia, and conquering the Iranian plateau; and reaching westward as far as the Levant and the Carpathian Mountains.

Hulegu Khan, also known as Hülegü or Hulagu, was a Mongol ruler who conquered much of Western Asia. As a son of Tolui and the Keraite princess Sorghaghtani Beki, he was a grandson of Genghis Khan and brother of Ariq Böke, Möngke Khan, and Kublai Khan.