Later in 1939 and into 1940, he served as the second general staff officer of Army Group A under Gerd von Rundstedt and Erich von Manstein, culminating in the invasion of France in the spring of 1940.
From 1941 to 1943, he served under Field Marshal Fedor von Bock, his wife's cousin, and later Field Marshal Günther von Kluge as chief operations officer of the German Army Group Centre in Operation Barbarossa, the invasion of the Soviet Union.