The Saga of Tanya the Evil, Vol. 3 (light novel) by Carlo Zen

Contrary to her dearest wish to find a safe place and stay there, Major Tanya von Degurechaff continues to wade through the fog of war with her troops on land, at sea, and in the air. After many battles with the increasingly numerous enemies of the Empire, a chance for a breakthrough finally appears. But when her comrades begin celebrating the glories they've reaped, savoring the sweet nectar of imminent triumph, Tanya alone is frozen in fear. Has the Empire decisively won the war, or is this nothing more than a Pyrrhic victory...?