Spartan Team Tau 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 two teams called in to assist Sigma Team over the course of the battle. They were attacked by covenant forces while investigating one of several downed Communication Arrays across Reach. They were pinned down, but rescued by Sigma, 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 Nelson-A122 and Louie-A199 provided cover in a Falcon, along with several others. However, when Dr. Calvin Roe detonated the building as he escaped, killing the four Spartans, the surviving members of Tau, Upsilon, Sigma, and UNSC personnel fled New Alexandria before it was glassed, and headed north to Outpost Foxtrot Whiskey. Roe's ship was shot down and he was eventually killed by Marco-025. However, coming under heavy fire, Martin-A136 of Upsilon was wounded, and was rescued by Nelson-A122 and Kane-099.
The team participated in the Battle for Outpost Foxtrot Whiskey, driving the Covenant back at the cost of another one of Upsilon Team's Spartans, detonating the base as they fled. Upon hearing a message from the Pillar of Autumn, The survivors headed there, only to miss the ship by minutes.Seeing that Covenant forces would soon arrive, Nelson-A122, Jax-007, Alex-A121 and Jordan-A111 stayed behind, hoping to buy the rest of the team more time to escape to a Frigate in a nearby shipbreaking yard. It is unknown what happens to them as radio contact was cut off several minutes after the others left. It is assumed that Nelson, the last survivor on Reach, was killed in action. The last two remaining members were absorbed into Sigma Team shortly afterwards and Tau was essentially dissolved.
List accurate as of March 2553 and Tau's official disbandment.