Which historical period forms the main backdrop of the first Assassin's Creed game?

The Third Crusade forms the main historical backdrop of the first Assassin's Creed game.

The story is set in 1191, during the conflict commonly called the Third Crusade. Altaïr travels among cities in the Levant, including Acre, Damascus, and Jerusalem, while the game presents a fictional struggle between Assassins and Templars within the era's political and military tensions.

Historical figures such as Richard the Lionheart and Robert de Sablé appear alongside fictional characters. The game uses real locations and broad historical circumstances but does not present a documentary account of the Crusade. Its conspiracy plot and secret orders are fictionalized elements of the series' mythology.

The period is sometimes confused with the First Crusade because both involved Jerusalem and the Levant. The First Crusade took place roughly a century earlier, whereas the original game's events are placed near the end of the twelfth century, during the Third Crusade.