Valor's Trial by Tanya Huff

 One of these days, I'm going to have to go back and re-read and review all of the other Huff books in the collection, the "Smoke", "Blood", and "Keeper" series. She's been turning out good tales for an amazingly long time. Gunnery Sergeant Torin Kerr gets a fresh assignment to take the greenest troops from Sh'quo Company into a brand new war zone against the Others. The battle doesn't last long, as some unknown party deploys a new type of weapon which vaporizes the entire battlefield and all of the troops from both sides...except for Kerr and a select few.

Kerr awakens in a cave complex which turns out to be a prison for Confederation Marines, monitored and run in some automated fashion by indeterminate parties - everyone knows that the Others do not take prisoners. The area where the gunnery sergeant awakens has descended into an anarchic situation where a strongman, "Colonel" Harnett, and his cronies have taken over, and rule over the weaker prisoners. Wounded arrivals are killed and robbed, and the survivors are kept in a state of near starvation to keep them cowed and suppression any sign of rebellion. Kerr arrives like a force of nature and single-handedly kills nine of the oppressors, puts the camp under command of the ranking genuine officer there, and proceeds to try to find a way to escape.

Other areas of the cave prison complex have actually managed to maintain military discipline, though most of the prisoners who have been there any length of time have been subtly drugged into complacency and are not interested in escaping. Kerr gathers a small band of those who have the will to leave and leads them on an adventure through the caves, cave-ins and earthquakes to an entirely new section, where they discover that there are Others imprisoned here, as well. She and the NCO from the enemy band, who have also been recently captured and still have the will to escape, manage to keep their troops from killing each other and pragmatically join forces to attempt to get out of the caves, off planet, and back to their home bases.

The wrap up to this story is pretty predictable, in my opinion, and I've suspected as much since about the third novel in the series. I won't spoil it for you here. This is another fun read that kept me up way too late finishing it.