D. Allen

Sergeant Dennis Allen was a United States Army member originally serving under Captain Roger Maxson.

Background
In 2077, Allen was amongst many soldiers in Mariposa to rebel against the United States government. However, during the Exodus from Mariposa to Lost Hills, a faction led by Allen split from the other members, taking some technology and weapons with them. Other members of the team included Soto, Jensen, and Camarillo.

After twenty days, they successfully made it to the West Tek Research Facility, but radiation levels began to rise as soon as the crater was in sight. They concluded that with their armor and Rad-X supplies they'd be fine for at least a day of exploring and that the technology they had the potential of recovering was worth it.

They climbed down the crater and explored the first two levels of the facility, unaware that the security sensors on these levels were destroyed. Upon entering the third level, the still-working sensors there triggered the security system and killed most of Allen's people. Allen tried to regroup, but only Soto and Camarillo made it back up to the first level with him. All three of them eventually died because of a power armor air filtration failure. Before he died, Allen logged what happened to the expedition into a holodisk which was later found by the Vault Dweller.

Appearances
Dennis Allen's remains appear only in Fallout.

Behind the scenes
In the Fallout Bible, it is claimed that Allen and his men deserted from the Brotherhood in 2134, despite Cabbot stating it occurred in 2077.