When the Devil Dances — John Ringo

TWO COMMANDERS, ONE HUMAN, ONE ALIEN, BOTH ALIKE IN DIGNITY

After five years of battling the Posleen invaders, human civilization is down to a handful of highly industrialized valleys where survivors create larger and larger engines of war to oppose the hated invaders.

After five years of battling the Humans, the Posleen are tired and angry. Humans don't fight fair. Even the Posleen are ready for a change: Tulostenaloor. Beaten before, he has learned his lesson well.

Now is the time: Two opponents of old squaring off in the battle that will define the course of the galaxy for the next millennia. And when Major Michael O'Neal, commander of the 1st Battalion 555th Mobile Infantry squares off against Tulostenaloor....

It is time to dance with the devil.