The Line Must Hold (Crimson Worlds #5)

The robotic legions of the First Imperium burst into human space, destroying everything in their path. Directed by the maniacal Regent, the enemy pressed forward with one goal: the destruction of mankind. The Superpowers of Earth, enemies for over a century, have banded together to face the threat from outside and their combined forces have fought delaying actions to buy time. But now, the Rim has fallen, and the heart of human space lies before the invaders. Erik Cain grimly leads his Marines and their new allies to Sandoval, to fight and hold that world against anything the enemy throws at it. But Cain plans more than just a defense: he intends to annihilate the enemy forces. And he'll sacrifice anything to win the ultimate victory. Even himself.