- Construction Platform 966A is decommissioned and abandoned.
- Madrigal is glassed by the Covenant. Survivors flee to a set of asteroids in orbit above Hesiod, dubbing the worldlets The Rubble.
- The Battle of Hat Yai takes place either late this year or in 2529.
- The MJOLNIR Security variant is created.
- The Assembly Minority decides to sacrifice remote, low-population colonies in order to determine the Covenant's pattern of operation and plan effective countermeasures based on it.
- January 30: James Cutter turns down a command position on board the UNSC destroyer UNSC Prophecy.
- February 13: The Battle of XI Boötis A takes place, resulting in a UNSC victory.
- December 5: Edward Buck enlists in the UNSC Marine Corps.