Mitchell Gant is an agent with the CIA.
Was an agent. And then wasn't and then was again but in conjunction with British Intelligence. And then he is back working for the Agency before saying a permanent goodbye and going to work in the private sector before, when we last find him, getting employment with the NTSB investigating suspicious airplane crashes.
Gant was born and raised in a small town of Clarksville in some midwestern state but the less remembered by him of that time the better for him, though we are told "Gant had never escaped from Clarkville. He carried it with him, wherever he went. It had shaped him". The one good thing he took from those early days was a love of flying that came to him when he was a young kid when a small plane landed on the county road and pulled into a service station for fuel.
As soon as he was old enough, Gant joined the U.S. Air Force and worked diligently to earn his wings and become a fighter pilot. The Vietnam War was going on at the time and he was naturally sent there for combat. When the F-4 Phantom he was piloting was shot down in a dogfight, he was nearly captured. His salvation would turn into a cause of PTSD when American planes dropped napalm in the area which provided him an opportunity to escape guerillas after him but he witnessed the horrific incineration of a Vietnamese girl travelling with the group; the nightmares from that would haunt him forever. He would leave the USAF with the rank of Major.
He would later get his first recruitment with the CIA but when that ended, his life did a nosedive and he took strongly to drinking. Sobriety comes when he is again approached by the Agency for the mission that comprises the first recorded adventure. The CIA/British Intelligence team wanted him because of his flying experience and because, thanks to his mother, he had a native's grasp of Russian.
Over the next few adventures, we will find Gant leaving the Agency yet again, trying and failing at marriage, and then finally finding a job that he seemed to actually enjoy.