(Capcom's primary storyline)
Delta Team was a unit within the Bioterrorism Security Assessment Alliance, identified as an SOU ("Special Operations Unit") within the BSAA's West Africa branch. In 2009, Delta Team, under the command of Captain Josh Stone, was deployed to handle the Kijuju Autonomous Zone Incident, in which it suffered near-total destruction.
In early 2009 it became clear to BSAA HQ that an outside agent had infiltrated the organization and was working against their plans for investigating Ricardo Irving and the suspected Plagas in the Kijuju Autonomous Zone. Perhaps to avoid making their suspicions clear, the BSAA Alpha Team was deployed as scheduled and subsequently walked into a trap laid out by Irving. Delta Team was quickly sent out to continue the mission in Alpha's absence, arriving in time to rescue SOA agents Chris Redfield and Sheva Alomar.
With Chris and Alomar heading off to search for Irving at a nearby quarry, Delta Team established camp at a village in the savannah, near the marshlands. Captain Stone and a few others took a boat out to investigate Irving's oil field, but Stone was forced into hiding when the team was attacked by parasitised tribesmen and the other operatives killed. The main bulk of the unit meanwhile were attacked and killed by an Ndesu at their camp. Team sniper Dave Johnson survived the attack after driving off to pick up Chris and Sheva, but was crushed by the Ndesu when he returned.
All members are equipped with SIG 556 assault rifles and a handgun (presumably a SIG P226) in their drop-leg holsters. It should be noted that both Johnson and Stone are seen using their 556 rifles as sniper rifles during Delta's first rendezvous with Chris and Sheva. Their standard issue handgun might either be a SIG P226 or a Beretta 92.