By Blood Alone: Legion of the Damned v.3 by William C. Dietz
It takes more than guts to win a war...In a Legion gone lax, Colonel Bill Booly, with his mixed-blood and by-the-book attitude, is a misfit. So when he steps on some important toes, his punishment is assignment to the worst post in the galaxy: Earth. But Booly and his troops will turn out to be Earth's best line of defense, when a Legion-led military coup topples the government...