Sigma-Beta Team was a unit of SPARTAN-II supersoldiers recruited as part of Project SIGMA. Singled out during training for their talents, the three members of Sigma-Beta Team were separated from their peers following their augmentation procedures and put to work on top secret operations organised by the Office of Naval Intelligence's Section Three. This trio of supersoldiers would work in the dark for years, securing important items for their superiors or helping to destroy the dying remnants of Human Insurrection in the colonies.
As the Human-Covenant War escalated, Sigma-Beta's missions would become increasingly dangerous as they spent weeks at a time behind enemy lines to sabotage Covenant bases or assassinate known enemy commanders, spreading chaos and discord with every operation. Despite their reputation for incredible luck in the field thanks to both their skill and general preparedness, Sigma-Beta Team would eventually meet its downfall during that Battle of Schönheit in 2545, when they were caught on the ground during the Covenant's brutal assault on the planet. With two members missing and presumed dead following the disastrous battle, ONI made the decision to formally disband the group, with its sole surviving member taking on solo operations afterwards.
Note: While rank and armour configurations match Sigma-Beta at the time of their disbandment, team member statuses are accurate as of September 2558.