The Saga of Tanya the Evil, Vol. 20 (manga)

The Imperial Army has allowed the Republicans to pull off their own version of Dunkirk right under its nose--and worse still, the General Staff doesn't even seem to recognize the significance of what is happening. Tanya, determined to get to the bottom of her bosses' sudden turn for the oblivious, flies to the imperial capital to see if she's simply been left out of the loop on some master plan, but even her bleakest suspicions don't hold up to what she finds there...