2531

• The Battle of Harvest. Preston Cole's fleet engages the alien warships responsible for the decimation of the Harvest colony. Six years after the planet was attacked, UNSC forces emerged victorious at the cost of two-thirds of the battle group.
• Cole is promoted to Admiral upon his return to Earth and learns that a number of outlying colonies have been destroyed, leaving behind no survivors.
• Cole begins to move his fleet around, trying to intercept the invaders. Ground and ship-to-ship battles begin in earnest, raging throughout the Outer Colonies. During one ground engagement, Human forces capture one of the aliens. Before succumbing to his wounds, interrogators learn that the aliens refer to themselves as "the Covenant" (roughly translated).

May

• May 1st: The Spartan-IIs Blue Team attack Camp New Hope, a United Rebel Front base located on planet Victoria in the 111 Tauri System, killing rebel leader General Howard Graves.
• May 1st: General Howard Graves of the United Rebel Front is killed by Spartan-IIs in Camp New Hope, Victoria, 111 Tauri System. Graves was killed by eight armed Asteroidea Anti-Personnel Mines..."John went to General Graves. A sliver of corrugated steel had lodged in the man's skull"

November

• November 7th: Spartans Kurt-051, Kelly-087 and Fred-104 are dispatched to investigate Construction Platform 966A for suspected Rebel activity. The mission is a ruse and Kurt is abducted by ONI to lead the Spartan III project. Kurt is 'officially' declared MIA.
• The UNSC Circumference is first noted. The UNSC Circumference was the ONI Prowler that abducted Kurt. It is later noted in the Battle of Reach.

December

• December 19th: Nicole-458 is born.

• December 27th: 497 recruits arrive at Camp Currahee on Onyx beginning the Spartan III program under the command of Spartan-051 forming what will later become Alpha Company.