From Halopedia, the Halo wiki
- February 13: Bliss is glassed by the Covenant.
- March 1: Preston Cole's Battle Group X-Ray reaches Harvest and the Second Battle of Harvest begins, achieving a Pyrrhic victory. However, the Covenant also claim victory and celebrate through fasting and prayer. The Prophet of Regret broadcasts the executions of "those who failed their duty" in the battle. The Covenant return to Harvest later in the year, leading to a five-year campaign for control of the planet.
- March 10: The WINTER CONTINGENCY protocol is enacted by the UNSC.
- March 23: Insurrectionists bomb civilian spaceport in Troisi City, Lodestone.
- April 2: UNSC forces working with ONI agents prevent an attack on New Harmony, Mars. Two Insurrectionists, Christina Rice and James McCann, were disguised as Army specialists and were stealing weapons for a possible attack.
- April 26: The Battle of Circinius IV takes place: the Covenant launch an assault on Circinius IV, killing almost the entire human population of the planet. SPARTAN-II Blue Team is deployed to retrieve survivors from Corbulo Academy of Military Science; only four cadets from Hastati Squad remain alive after the initial assault, three of whom make it to the extraction point and evacuate as the planet is glassed.
- April 28: Vice Admiral Michael Stanforth requested for the Office of Naval Intelligence to repurpose all assets to aid the war against the Covenant and to refocus all research on wartime strategy.
- May 3: Dr. Catherine Halsey devises a new matrix strata with random-access couplers that could theoretically expand an AI's lifespan. Those protocols are authorized by Vice Admiral Michael Stanforth some time later.
- October 21: The Battle of Alpha Aurigae takes place in the Alpha Aurigae system.
- Biko is glassed by the Covenant sometime during this year.
- The Committee of Minds for Security analyze the Covenant's glassing capabilities based on recorded data from prior engagements. They also discuss changing the primary focus of the UNSC Special Forces, with the protection of infrastructure, previously the main focus of the Spartan-IIs, being shifted to the ODST. Later in the year the Committee discuss the possibility of a hypothetical Covenant counterpart to the Assembly and the possibility of contacting it.
- ^ Bungie.net: CAA FACTBOOK/UNSC Operational Reports-Γ
- ^ a b Halo 4: Forward Unto Dawn, Part 1
- ^ Halo 4: Forward Unto Dawn
- ^ Halo Waypoint Forums - Today in Halo
- ^ a b Halo: Reach, Dr. Halsey's personal journal
- ^ Hunt the Truth, Xenophobia
- ^ Halo: Reach, Data pad 10
- ^ Halo: Reach, Data pad 11
- ^ Halo: Reach, Data pad 12