A proponent of the Blitzkrieg tactics, he used tanks in large formations in the conquest of Poland (1939) and of France (1940). As commander-in-chief of the Panzer (tank) forces, he played a leading role in the German victories of 1940–41, but was dismissed when he disagreed with Hitler’s order to stand fast in the 1941–42 Soviet counter-offensive outside Moscow. In 1944 he became chief-of-staff to the German Army High Command, but in March 1945 was again dismissed, this time for advocating peace with the Western Allies.