Valentine's Resolve by E E Knight

After three years of exile from humanity’s war against the Kurians, David Valentine returns to battle. The Lifeweavers, Earth’s allies in the conflict, have mostly vanished, but those that remain are held captive by an overlord known as the Seattle Kurian. To free them, Valentine must convince the legendary resistance fighter known as the Marshal to join his cause. But the Marshal is something of an overlord himself…