The Crusades refers to the hundred year war between humans and Gears. The war began when Justice took control of the Gear army in 2074 and attacked Japan. Immediately after, the United Nations formed the Sacred Order of Holy Knights to counter the threat. The war ravaged the earth and dissolved a number of nations. The war finally ended in 2175 when the Holy Knights, led by Ky Kiske, sealed Justice in an alternate dimension. However, in the Alternate Timeline created by I-No, the war dragged on for ten more years because of Ky Kiske's death in the Battle of Rome.