Childe Cycle # 5: The Spirit of Dorsai by Gordon R. Dickson

Throughout the universe, the Dorsai are feared and respected as the most effective soldiers humanity has ever known. But the warrior spirit of the Dorsai does not, cannot, reside solely in the men of that race – for when the Dorsai go to fight wars on distant planets, it is the women who remain behind to defend their world and their future. The home planet of the Dorsai has never fallen to any invader, although many have tried…