Take the Shilling

"[U]nusual among military science fiction for its concentration on the psychology and politics of societies in conflict."
—Analog, on the Confederated Worlds series

The Confederated Worlds implanted in his brain the skills to make him a soldier.  He still had to learn how to survive interstellar war.

Tomas Neumann sought escape from his backwater planet and overbearing mother, and a mentor to replace his long-dead father. "Taking the shilling"—enlisting in the Confederated Worlds military—promised both. But despite the soldier's skills implanted in his brain, combat still threatened to destroy him, in body and in spirit. Grieving for lost comrades, demoralized by a spiral of atrocities, could Tomas learn what he needed to survive, before facing his war's ultimate challenge?