Which historical war forms the main setting of the original Assassin's Creed?

The Third Crusade forms the main historical setting of the original Assassin's Creed. This crusade took place from 1189 to 1192 as European rulers attempted to recover Jerusalem after its capture by Saladin.

The game follows Altaïr Ibn-La'Ahad, an Assassin operating in cities such as Masyaf, Jerusalem, Acre, and Damascus. Historical figures including Richard the Lionheart and Saladin appear in the story, though the game combines documented history with fictional characters and conspiracies.

The Third Crusade is sometimes confused with the broader medieval Crusades. It was a specific campaign led by Richard I of England, Philip II of France, and the Holy Roman Emperor Frederick Barbarossa, although Barbarossa died before reaching the Holy Land.