During the invasion of Poland in September 1939, Zeitzler was Chief of Staff to General Wilhelm List, commanding the XXII (Motorized) Corps in the 14th Army. In March 1940 he became Chief of Staff to General von Kleist, commanding Panzergruppe A, later redesignated 1st Panzer Army. During the Battle of France, Zeitzler brilliantly organized and managed the panzer drive through the Ardennes. He continued in this post through the successful Invasion of Yugoslavia and Battle of Greece. On May 18, 1941 Zeitzler was awarded the Knight's Cross of the Iron Cross.