William Kendall is the chief Troubleshooter for the Joint Chiefs of Staff.
As such this experienced Colonel is given operational control over a group of highly trained officers, dubbed the Special Unit. The purpose for this highly secret unit is to strike at the enemies of the country, foreign or domestic.
The field leader of these men, and nearly warranting a co-billing, is Kendall's friend, Lt. Colonel Aaron Eisenberg. Together they decide which missions are to be taken and then lead them. At times it is Eisenberg in the field while at times it is both Kendall and Eisenberg. Eisenberg is a highly capable officer who might have made full colonel if he didn't have a habit of baiting superiors, like the Chairman of the JCS.
Kendall does not have such a problem. By no means a yes-man, Kendall nevertheless is willing to hold his tongue long enough to make what he said less biting. But diplomacy flies out the window when his path is hampered by bureaucracy or pass-the-buck mentality.
The origin of the men and the people to whom they answer is the military but the actions they perform are far closer to traditional covert intelligence work than true soldiering.
While much of the activity in the four-book series is military in nature, Kendall was the chief Troubleshooter for the JCS before the creation of the Special Unit and is only just getting used to working with a group. Prior to it, he was a loner and still thinks about hitting the field himself before passing the assignment to others.