How long before Halo: Combat Evolved is Operation METEORITE set?

Operation METEORITE is set one year before Halo: Combat Evolved.

The prequel missions take place in 2551, while the main events of Halo: Combat Evolved occur in 2552. That placement makes the arc an earlier chapter in Master Chief’s military history and gives the story room to show his relationship with Sergeant Major Avery Johnson before the events aboard Installation 04.

The timing is significant because Operation METEORITE is not simply a prologue that begins moments before the Pillar of Autumn reaches the ring. It is a separate operation from the preceding year, involving a covert infiltration of the Covenant vessel Triumph of Tolerance above Promise, a human colony devastated by the Covenant.

A common mix-up is placing these missions immediately before Combat Evolved or after the Fall of Reach. Chronologically, the operation predates Halo: Reach’s 2552 storyline as well as the original ring campaign, even though the remake may recommend playing the new missions after the main campaign for narrative impact.