After the German annexation of Austria in 1938, Rendulic joined the Wehrmacht as a Generalmajor (U.S. equiv. brigadier general). From September 1939, he served as a division and corps commander in Poland, France, and the Soviet Union. Between April 1943 and June 1944, he commanded the Second Panzer Army in the Balkans. In the course of conducting antipartisan warfare, Rendulic's army committed numerous war crimes against civilians.
At the end of June 1944, Adolf Hitler appointed Rendulic commander of Twentieth Mountain Army, with the rank of colonel general. He led his retreating army from Finland to Norway and commanded German forces in Norway from December 1944 to January 1945. In October 1944, Rendulic ordered the complete destruction of all means of subsistence and evacuation for the entire civilian population of northern Norway. During October and November 1944, this order was ruthlessly carried out. Rendulic then demonstrated a remarkable administrative capability, as he organized the retreat of 200,000 men across the Arctic, with few roads available.
In succession, Rendulic next commanded Army Group North (January to March 1945), Army Group Kurland (March to April), and Army Group South (April to May). At the end of the war, he fought the Soviets in Austria. Tried and convicted at the International Military Tribunal at Nuremberg, he received a 20-year sentence but was released in December 1951. He then published several books on his wartime experiences. Rendulic died at Linz, Austria, on 17 July 1971.
Rendulic, Lothar. Gekämpft-Gesiegt-Geschlagen. Wels, Austria: Welsermühl, 1952.; Ziemke, Earl. The German Northern Theater of Operations, 1940–1945. Washington, DC: U.S. Government Printing Office, 1960.