World War II in Europe began on Friday 1 September 1939 when German forces invaded Poland. Peltz flew 45 combat missions with his "Staffel" against Poland, attacking railway lines, traffic junctions and bridges as well as the Bombing of Wieluń. For his services in Poland he received the Iron Cross 2nd Class () on 15 September 1939. During the Battle of France, beginning on 10 May 1940, he flew with the same "Staffel" which was renamed to 1. "Staffel" of "Sturzkampfgeschwader" 3 (StG 3—3rd Dive Bomber Wing) on 5 July 1940. Again he targeted railway lines, traffic junctions and bridges. In addition he attacked shipping at Calais and during the Battle of Dunkirk sank a transport vessel. In total he flew eight missions against Dunkirk and was awarded the Iron Cross 1st Class () on 22 May 1940. He flew an additional 57 missions before the campaign in France came to an end on 25 June 1940. In total, Peltz flew 102 combat missions over Poland and France, leading his "Staffel" through these campaigns without loss.