The Saga of Tanya the Evil, Vol. 16 (manga)

After somehow managing to live through the most grueling battle of their entire careers, Tanya and the 203rd receive a letter from the General Staff. Its contents are, essentially, "Hop on these rockets and go smash up the Republican Army's HQ. Oh, and be sure to come back from this technologically unprecedented flight alive once you're done with your absurdly dangerous mission!"