Joe Haldeman 
Forever War #3 [PDF ebook] 

Still reeling from the massacre on Aleph, the survivors are speeding across space, pursued by a Tauran cruiser. Mandella, shaken but not driven insane by the events he witnessed on the planet, is still pondering the machinations of an army that would choose to embed such terrifying conditioning in its soldiers.But his time among the stars is coming to an end. If he can just make it to the Stargate, his tour will be over and he can return to life as a civilian on Earth… at least, that’s what he hopes.