Halo: Combat Evolved begins with the UNSC Pillar of Autumn emerging out of slipspace after the Fall of Reach, only to find a huge ring world—a "Halo"—floating in space. Master Chief Petty Officer John-117 (although his name is never mentioned throughout the game), a SPARTAN-II, is aboard the Pillar of Autumn when the ship comes under attack by the Covenant, a religious alliance of aliens and the archenemy of humanity.
