Hammer’s Slammers # 6: The Warrior by David Drake

They were the best.
Colonel Alois Hammer: He welded five thousand individual killers into a weapon more deadly than any other in the human universe.
Luke Broglie: His brilliant mind could have succeeded in any business; but war was the business he chose.
Tess Kuykendall: She knew what her job was, but she also knew what was survivable.
Slick Des Grieux: War was his life, and that made him almost too dangerous to live.
The collision between different styles of being The Best meant a bloodbath, even by the grim standard of Hammer’s Slammers