Fireteam Crimson

Fireteam Crimson is a combat team of SPARTAN-IV supersoldiers of the UNSC. Crimson consisted of four members and was present aboard UNSC Infinity in February 2558 during the Second Battle of Requiem, and were also responsible for stopping the Promethean Invasion of the Galaxy, during the Third Battle of Requiem.

Second Battle of Requiem
Fireteam Crimson was deployed in tandem with Fireteam Majestic to clear out Forerunner structures. Crimson cleared their structure first, much to the annoyance of Majestic. As the battle of Requiem raged on, fireteam Crimson managed to assassinate Parg Vol, a Sangheili terrorist. Later, in pursuit of Jul 'Mdama they managed to secure a Forerunner device known to the Covenant as The Didact's Gift.

They were captured by the Covenant on a search and rescue op for Gabriel Thorne but escaped, and began a series of crippling surprise attacks on the Covenant using a Phantom flown by Lieutenant TJ Murphy before being recalled to Infinity, which was under attack. After crashing in the hangar, they disarmed several stolen HAVOK Tactical Nuclear Weapons, turned the rear outer defenses back online, and thus secured the Infinity.

They were tasked by Infinity to assist with the deactivation of one of the two Artifacts that was holding Infinity in Requiem's gravity field. After succeeding, they raced to Infinity in a Pelican while Requiem was pulled into its own sun. Though Crimson was able to make to the Pelican, their dropship was shot down by a Promethean Hailfire, causing the dropship to crash in the nearby woods. Crimson would remain knocked out, until the planet collided with its sun, causing a huge supernova.

Infinity departed the system, just as Requiem was pulled into the sun, declaring Crimson KIA, and escaped through Slipspace, due to not having enough time to organize a second rescue.