L. E., Jr. Modesitt: The Parafaith War [1998] paperback

Trystin Desoll is a young officer of Anglo descent in the culturally Shinto Eco-topian Coalition. In the battle to hold back the expansionist Revenant theocracy, Trystin faces ever-tougher challenges from the enemy forces on the ground and in space, while at home he must confront the beginnings of prejudice from his own people because of his Revenant looks.

The war is weakening both societies, and more ominously, is forcing the Farhkans, a race of technologically superior aliens, to question whether mankind in general can be a peaceable neighbour. Trystin is the only one in a position to stop the war, but to do so, he must somehow overcome the prejudices of his culture . . . and become the prophet of his enemy.