Major Mitchell was a high achiever despite his relatively young age of thirty. Impressed by his work, his superiors assigned him the position of supervising operations at Area 51, where he was responsible for everything that happened on the base except research which was headed by Dr. Brackish Okun.
During the War of 1996, Mitchell greeted the arrival of President Thomas Whitmore and his staff to Area 51. Mitchell was later part of Whitmore's security detail when the President interrogated a captured alien. When the alien attempts a psychic attack against Whitmore, Mitchell and the security detail killed it.
During the July 4th counteroffensive against the aliens, Mitchell oversaw to recruit and brief able volunteers including Russell Casse, and later helping refugees to take shelter inside Area 51 when the aliens began their attack on the base. Mitchell was present to overhear Casse's decision to sacrifice himself to destroy the City Destroyer, saving everyone in the process. Mitchell gave some comfort to Casse's eldest son Miguel, solemnly telling Miguel that his father had been a brave man.