Youjo Senki: Saga of Tanya the Evil

What is Youjo Senki: Saga of Tanya the Evil about (plot, summary)
Tanya Degurechov used to be one of Japan's elite office workers, but because of a wrathful god, was reborn as a little girl. She has blonde hair, blue eyes, and nearly transparent white skin, and she flies through the air and mercilessly strikes down her opponents. She speaks with a young girl's lisp and commands the army. Tanya prioritizes optimization and career advancement above all, and she will become the most dangerous entity among the Imperial Army's sorcerers.