Second Chances - Michael Simon

Humanity's war with the Coven is going badly.

Fleet simply doesn't have the ships or the manpower to counter the alien's vast reserves, so Cole Jackson is hauled out of his self-imposed exile and ordered back to the front. The Admirals are gambling on a miracle; that he and his crew can repeat the success of his First Command by repairing vessels and sending them into battle. And maybe snatch victory from the jaws of defeat.

Fleet has been gathering damaged and deserted ships in a remote system on the edge of human-controlled space. Without transport, Jackson's crew must travel on an obsolete military simulator, without shields or weapons. When they run into a Coven warship, it's all Jackson can do to keep them alive as both ships crash-land on the planet.

In a running battle with cyborg warriors, Jackson must avoid alien patrols, build rudimentary weapons, and cobble together some type of ship that would see them escape the death planet and change the course of the war.