Monstrous Regiment Discworld Series, Book 31.

War has come to Discworld...again. And, to no one's great surprise, the conflict centers around the small, insufferably arrogant, strictly fundamentalist duchy of Borogravia, which has long prided itself on its ability to beat up on its neighbors. This time, however, it's Borogravia that's getting its long-overdue comeuppance, which has left the country severely drained of young men. Ever since her brother Paul marched off to battle a yea...