During World War II, Hoover was sent to Casablanca, where his first major assignment was flight testing the assembled aircraft ready for service. He was later assigned to the Supermarine Spitfire-equipped 52d Fighter Group in Sicily. On February 9, 1944, on his 59th mission, his malfunctioning Mark V Spitfire was shot down by Siegfried Lemke, a pilot of Jagdgeschwader 2 in a Focke-Wulf Fw 190 off the coast of Southern France, and he was taken prisoner. He spent 16 months at "Stalag Luft 1", a German prisoner-of-war camp in Barth, Germany.