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The Third Fleet was a numbered expeditionary fleet in the UNSC Navy. The Third Fleet participated throughout the Human-Covenant War. Early in the war, the fleet was led by Admiral Preston Cole, where the Third Fleet participated in the Harvest campaign and later the Battle of Arcadia. The Third Fleet was still active by the time of the Battle for Earth in 2552, where the fleet combined its strength with the Home Fleet.
Harvest campaign and Arcadia
The Third Fleet was commanded by Admiral Preston Cole early in the war and took part in the extended campaign to recapture Harvest from the Covenant, where the Third Fleet engaged the Fleet of Glorious Interdiction led by Arbiter Ripa 'Moramee. On January 3, 2531, Cole led Battle Group D of the Third Fleet to a staging area in interstellar space, where UNSC Spirit of Fire joined the battle group. Meanwhile, the rest of the fleet continued to engage Covenant forces over Harvest. While investigating Covenant activity on Harvest's surface, UNSC Prophecy was attacked by Covenant forces. While she managed to repel the attackers, Prophecy was damaged and her reactors went critical; Commander Orez of the Office of Naval Intelligence informed Cole of the incident. Unable to spare a combat ship to rescue the crew of Prophecy, Cole dispatched Spirit of Fire for the mission. However, arriving three days after the incident occurred, Spirit of Fire could only rescue the dying survivors of Prophecy and initiate the ship's self-destruct sequence. Meanwhile, by February 4, 2531, Battle Group D had rejoined the rest of the Third Fleet to engage Covenant forces over Harvest.
Despite incredible losses over the course of the five-year siege, the Third Fleet was able to finally drive away the Covenant forces at Harvest. Following the battle, most of the Third Fleet returned to Reach in the Epsilon Eridani system for drydock repairs. Meanwhile, the crew of Spirit of Fire discovered that a relic the Covenant had found on Harvest contained coordinates that led to the Outer Colony of Arcadia. With Cole's permission, Spirit of Fire broke from the Third Fleet and traveled to Arcadia. On February 9, 2531, Spirit of Fire arrived at Arcadia, where she promptly engaged Covenant forces from the Fleet of Glorious Interdiction. Cole soon led the Third Fleet to Arcadia to aid Spirit of Fire in battle, where he succeeded in driving Covenant forces away from Arcadia. However, Spirit of Fire was lost when she pursued Covenant forces to an unknown region of space.
Battle for Earth
Years later, in the final months of the war, the fleet was commanded by Vice Admiral Williams. Following the Fall of Reach, the Third Fleet and all remaining assets of the UNSC Navy were recalled to the Sol system, where they were consolidated into a single command grouping under the Home Fleet, effective September 5, 2552. As approved by UNSC High Command and the UEG Security Council, Fleet Admiral Joseph Harper of the Fifth Fleet was given administrative and tasking authority of all fleet elements in the Sol system, though the Third Fleet and its fellow fleets retained administrative control over their battle groups.
On October 10, 2552, the Third Fleet's Battle Group Rhino detected twelve unidentified large vessels in the system broadcasting outdated civilian IFF codes. Upon approach, eleven of the vessels made unauthorized slipspace transits from the Sol system. Pursuant to standing orders to engage vessels not positively identified as friendly, Battle Group Rhino moved to engage the remaining ship. UNSC Totem Lake was subsequently lost with all hands after reportedly suffering multiple hull breaches and boarding parties. The battle group then disengaged and regrouped at Phase Line Alpha above Enceladus. Williams requested permission from Harper to attack the ship, but permission was denied. The brief spout of violence in which Totem Lake was lost came to be known simply as the Battle of October 10, and was later reported on by Captain W. Murray.
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