Tau Team was a six-man SPARTAN-III team formed from survivors of Operation: PROMETHEUS that fought in a number battles during the Human-Covenant War, including the Siege of Fargad and Fall of Tywan II. By 2552, they were stationed on Reach when the Covenant began their invasion. Tau was one of several teams called in to carry out reconnaissance in enemy-held territories, and were attacked by Covenant forces while investigating one of several downed communication relays across Reach. In the midst of the firefight they received reinforcements from the SPARTAN-II Sigma Team, who had just arrived on the planet. After wiping out the attackers they reported back to base, only to find similar reports from teams Upsilon and Noble, who were investigating other relays at the time. A few weeks later, Tau accompanied Sigma on a mission to destroy a Covenant Supercarrier before it entered atmosphere. Operation:DROPKICK is initiated as a follow up to Operation:UPPER CUT. Using Sabre starfighters, the team entered and destroyed the ship, losing Frank-A103 and Dom-A178 in the process. The others escaped via Pelican to the planet's surface.
The Pelican took them to New Alexandria, which was under attack by the Covenant. They were ordered, along with Upsilon team, to assist in thee extraction of ONI personnel from a facility that was under attack by enemy forces. Three members of Upsilon and Wulf-041 began to clear the building while Tau and their allies fended off wave after wave of alien attackers. However, when Doctor Calvin Roe detonated explosive charges prematurely and killed four Spartans, the survivors pursued his ship out of the city and headed north to Outpost Foxtrot Whiskey. After the killer was taken care of, Tau contributed to the defence of the base, driving the enemy back at the cost of one of Upsilon Team's members.
They would remain on Reach for some time, trying to regain contact with HIGHCOM unsuccessfully before deciding to abandon the doomed colony world entirely. Tau and the other Spartan teams headed for Aszod at first, hoping to board the UNSC Pillar of Autumn. Missing the vessel by minutes, they fought valiantly against an approaching Covenant army while their comrades secured another vessel: the UNSC Bright New Day. Jordan-A111 and Nelson-A122 would give their lives to save the rest of their comrades, who managed to board the damaged Frigate and escape Reach successfully. In the aftermath of the Fall of Reach, the two remaining members were absorbed into Sigma Team, essentially dissolving Tau Team as a unit.
List accurate as of March 2553 and Tau's official disbandment.