The Saga of Tanya the Evil, Vol. 10 (light novel): Viribus Unitis

Time is not on the Empire's side. It has become painfully clear that simply winning battles will not be enough to turn the tide of this war. Having no interest in sharing the fate of her country, Tanya immediately decides to do the only thing that makes sense—look for a new job! Of course, she'll have to proceed with extreme caution, because her current employer isn't some random company but the Imperial Army. As it happens, she isn't the only one ready to do something drastic when push comes to shove...