Steiner fought both in the invasion of Poland in September 1939 and the campaign for France in May and June 1940. In 1940, Steiner formed a motorized SS division based on a recruiting program for volunteers from western and northern European countries. He commanded this "Viking Division" (5th SS Panzer Division) in Operation barbarossa, the invasion of the Soviet Union. During the 1942 German summer offensive, the division pushed through the south of Russia and reached Kuban. In 1943, Steiner commanded the III ("Germanic") SS Panzer Corps, and on 1 July 1943, he was promoted to Obergruppenführer and then to general of the Waffen-SS.
During the final battle of Berlin, Adolf Hitler ordered Steiner to seal a gap through which Soviet forces were pouring, hoping in vain that Steiner might be able to turn the tide of battle. With few men and little equipment, Steiner was unable to accomplish anything. He surrendered to British forces on 3 May 1945. Not released until April 1948, Steiner subsequently published two books about his military career. Felix Steiner died on 17 May 1966 in Munich.
Koehl, Robert Lewis. The Black Corps: The Structure and Power Struggles of the Nazi SS. Madison: University of Wisconsin Press, 1983.; Mathias, Karl Heinz. Felix Steiner: General der Waffen-SS und seine europäschen Freiwilligen. Riesa, Germany: DS-Verlag, 2002.; Stein, George H. The Waffen SS: Hitler's Elite Guard at War, 1939–1945. Ithaca, NY: Cornell University Press, 1966.