Hasan-i Sabbāh (Persian: حسن صباح) or Hassan as-Sabbāh (Arabic: حسن بن الصباح الحميري, full name: Hassan bin Ali bin Muhammad bin Ja'far bin al-Husayn bin Muhammad bin al-Sabbah al-Himyari; c. 1050 – 12 June 1124) was the founder of the Nizari Isma'ili state and its fidā'i military group known as the Order of Assassins, often referred also as the Hashshashin. Since Marco Polo, he has been known in the West as the Old Man of the Mountain. He later seized a mountain fortress called Alamut.