Son of Orlan - The Chronicles of Kin Roland, #2

Kin Roland survived the Battle of Crater Town. He managed to keep his friends alive, though most remained at his side on Crashdown when the safe course would have been to evacuate with Earth Fleet. Kin even found the girl of his dreams. Surviving Earth Fleet justice and a Reaper vendetta was only the beginning. Now Kin has real trouble. With the  Grand Army of the Mazz Empire descending on the planet to destroy ancient enemies and Reapers sweeping across the landscape leaving terror and death in their wake, Kin learns the truth of his supposedly invincible enemies.
The largest military expedition in history isn't that of of a conquering force. The Mazz are on the run--fleeing extinction and Kin knows desperate enemies are dangerous. Kin will find himself in a position no one expected. He'll define humanity with his next choice, or doom them eternally.