The Corpse Bug War

The first memory John can remember is when he was five years old listening to the "bombs bursting in air" which he thought were fireworks for the Fourth of July. But they weren't, they were actually bombardments of where he lived with his parents in Los Angeles. These were a direct assault on humanity by the Corpses, enemy aliens all mankind was at war with. As he grew older his parents were killed and he was turned over to Space Command's space marines. These troopers were sent far and wide to world after world after training. When he was ready he was assigned distant duty many, many light years from Earth which no one expected him to ever return from. Battle after battle he survived eventually to receive high enough rank to be in direct line of officer succession of the Field Marshall himself in charge of all armed forces. Then, after a bitter encounter he made suggestions of force deployment because there were no orders coming through. This bitter battle was won but he was now in charge of all military operations of some fifteen colonial worlds they had just liberated. His forces in disarray, all ships and most equipment in need of repair, his marines and mobile infantry exhausted they no longer have contact with Earth. The most likely scenario is that the Corpses have taken Earth, no survivors. Facing the reality he is in command of the last of Earth's forces, such as they are, the only question is can he save the last of all mankind in a job no one else will take?