Strike Witches: Erica Hartmann 1941

Following the story of Erica Hartmann, this tale details her early years spent training in the JG52 alongside other powerful witches like Gertrud Barkhorn and Adolphine Galland. When a Neuroi invasion plagues Europe, witches from Karlsland and Britannia team up to defeat the enemy. This is considered a character-focused prequel to the famous Strike Witches series.
(Source: The Misfits Squadron)