Who are the Engagés in the novel, Under Fire?

Engagés is the name given to the French soldiers who volunteer in peacetime to serve 3-5 years, and in exchange are given the right to chose their arm of service, with some qualifications. Engagés are consider by some members of Bertrand's Squad as integral parts of the war effort, deserving of honor, but by others as part of the vast network of "shirkers."