Mongol forces under Hulagu enter and dismantle the Nizari Ismaili (Assassin) stronghold at Alamut Castle (in present-day Iran) as part of their offensive on Islamic southwest Asia.

Mongols are an East Asian ethnic group native to Mongolia and China, as well as the republics of Buryatia and Kalmykia in Russia. The Mongols are the principal member of the large family of Mongolic peoples. The Oirats and the Buryats are classified either as distinct ethno-linguistic groups or as subgroups of Mongols.

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.

The Nizari state was a Nizari Isma'ili Shia state founded by Hassan-i Sabbah after he took control of the Alamut Castle in 1090 AD, which marked the beginning of an era of Ismailism known as the "Alamut period". Their people were also known as the Assassins or Hashashins.

The Order of Assassins were a Nizari Isma'ili order that existed between 1090 and 1275 AD, founded by Hasan al-Sabbah.

Alamut is a ruined mountain fortress located in the Alamut region in the South Caspian, near the village of Gazor Khan in Qazvin Province in Iran, approximately 200 km (130 mi) from present-day Tehran.