This is an Omnibus version of the novels Forever War, Forever Free and Forever Peace.
Joe Haldeman was drafted into the Army and served as a combat engineer in Vietnam. Forever War was inspired by his wartime experiences.
William Mandela is conscripted into the United Nations Exploratory Force (UNEF) for a war with the mysterious Taurens. The training is gruelling and realistic, the recruits don’t die like flies but it is close. The aliens where discovered when they started attacked human colony ships, that is at least the official truth. UNEF is being sent out for revenge and information. Their first target is an alien colony, which turns out to be unarmed. Their first fight is a walkover but they fight many more battles and they aren’t as one sided.