Mitchell began his career assigned to the 24th Infantry Division at Fort Stewart, Georgia. Having served during the Persian Gulf War, Mitchell was with the 5th Special Forces Group at the beginning of the Invasion of Afghanistan. Entering Afghanistan via helicopter, Mitchell and other members of his special forces group began to work with Abdul Rashid Dostum of the Northern Alliance, travelling on horse back. In late November 2001, Mitchell responded to Mazar-e-Sharif and led a fifteen-person special forces team, made up of British and Americans, to stop a prison uprising involving John Walker Lindh at Qala-i-Jangi; for his actions he was awarded the Distinguished Service Cross, and a Navy SEAL was awarded a Navy Cross. Mitchell was later involved in the capture of Mohammad Fazl. In 2003, he deployed to Iraq. Later that year he traveled to MacDill Air Force Base, where he received the Distinguished Service Cross for his actions leading the effort to quell the Taliban's offensive at the Battle of Qala-i-Jangi in 2001. CIA Director George Tenet, the widow of CIA officer Johnny Micheal Spann, and others attended the award ceremony.