Michael Pössinger joined the mountain troops of the Wehrmacht in October 1937, and took part in the Invasion of Poland (1939) and the Battle of France (1940). He was awarded the Knight's Cross of the Iron Cross on 19 July 1940. In 1941, he fought in the Balkans Campaign and Operation Barbarossa. In 1941 Pössinger participated in the FIS Alpine World Ski Championships 1941 at Cortina d'Ampezzo in Italy and won a Silver Medal.