*poggy again take this with a grain of salt* The fall of Masyaf was an event during the mid-13th century in which Genghis Khan's grandson Hülegü Khan led an assault on the Assassin fortress of Masyaf in an attempt to annihilate the Order for their part in his grandfather's death in 1227.
The attack caused the ultimate disbandment of the Assassins residing in Masyaf, which was completely deserted before the Mongols could claim their victory. Prior to the siege, the majority of the Assassin strongholds east of the Levant had already been destroyed.