The Saga of Tanya the Evil, Vol. 12 (light novel) by Carlo Zen

Tanya has won victory after victory on the battlefield, and still the Empire hurtles toward its destruction. Zettour stands at the helm, a warped sense of patriotism guiding his actions as he prepares the stage. His only goal now is to secure the best possible defeat the Empire can afford, even if it means going down in history as the greatest villain of all time. And to make that happen, he’ll do whatever it takes to shock and awe the world, starting with Ildoa. The time for diplomacy or reason has passed. There is only war.