Mike Brent is a Green Beret seconded to the CIA.
Brent, holding the rank of Captain, is an experience soldier who was once placed in charge of eleven men, all Special Forces. This highly trained team was assigned to the CIA to go where fighting was needed instead of subtefuge. The missions were invariably deadly and lives were lost in the fight. With the large number of missions the team had been on, attrition had been high and only 4 were left as the series begins and even that would change quickly.
A member of the Ninth Special Forces, Brent had a great deal of respect for the men that he has lost and carries a personal burden over their deaths. His second-in-command, the one non-Beret of the group, has less of a problem with it, not through any animosity but through having been in war so long on so many fronts he is inured. This man is Hans Schmidt, a former German Wehrmacht with a chest full of medals to show his bravery. Brent and a teammate wonder, though, whether the solemn soldier might not have been an SS officer for the coldness he often shows.
The first book is almost totally a military operation, even though the assignment was given them by the CIA. The second book details a far more covert mission, undercover, still for the Agency but with Brent and Schmidt taking the role of businessmen. This is not a situation to which they are accustomed, however, as they laugh together about their situation. Schmidt comments that "the tiger does not change its spots" but still, they try.