Briggs Tanner is an agent for US Intelligence.
He has been one for over fifteen years by the time we first meet him and through that time has had some amazingly close calls, surviving by his wits which are many and his skills which are more.
While serving in the Naval Special Warfare department, Tanner was selected for an elite detachment called the Intelligence Support Activity Group. These "warrior spies" were a combination of soldier willing to engage in black ops if necessary and spy able to fit in any surroundings. Two years of rigid training followed, honing his skills to the limit. Tanner not only excelled, he seemed to thrive on the challenges.
When the program was scrubbed due to policy changes, Tanner, suffering the loss of his wife from disease, decided to resign his commission for the civilian world. Without his mate and without the excitement that came from his dangerous work, though, the civilian life was far too empty to be endured long. He did not fit in. He was in his late 30's, had seen far more action and trouble than anyone around him, and had few friends to socialize with and certainly no one with whom to relate.
Which explained his willingness to again accept an offer for a chance to risk his life when he was asked to join a new intelligence agency called Holystone. Established by President Reagan, this small bureau was tasked with handling special cases where "military action was too much, diplomacy was too little, and standard intelligence measures were indefensible." It would take only the best.
That meant people like Tanner.