Books like The Mercenary

Falkenberg's first lesson is that loyalty is to the fleet and not to the precarious coalition government of Earth. His second is that the navy's mission is to exist, preserving the peace in the far-flung corners of the galaxy in the hope that at least some portions of the human race may be saved when Earth destroys itself... The Mercenary is a parable for our times: the dirt of politics, the evil of war, the loneliness of command, and the rewards of comaradeship...