Mike Banning is an agent with the American Secret Service.
He has been with that department for a considerable number of years putting in outstanding work resulting in impressive results, so much so that he had some time before the first recorded adventure moved to the prestigious but incredibly stressful job of Presidential Protection Duty. After a couple years at this he has been promoted to being the leader of the detail.
Prior to his employment in the Secret Service, Banning has served in the U.S. Army, part of the elite 75th Ranger Regiment. Born in 1970, Banning was raised for a short time in Fort Hood where his father, also a Ranger, was stationed. Then for reasons not divulged (or perhaps even known), his father abandoned his family and his mother was left to raise her son. She died a few years later.
Now in his early 40s at the time of the first adventure, Banning is a strong, impressive man with a burly face, not handsome by any definition but with considerable character and clearly showing strength and resolution; it would not be possible to look at him without knowing that causing him trouble would not be in the best interest of any would-be instigator.
When he is put in charge of the protection of the Chief Executive, he also became close to the man and it would not be out of line to state the two had become friends; Banning would not be considered an advisor to the man in any way but he was a very good listener and he would hear without judgment.
One final key point that Banning will demonstrate several times in the adventures we have of him and that is that he does not like to lose and giving up is something he is incapable of considering.