Panzer division
This unit was subordinated to the 2nd Panzer division during the Invasion of Poland and fought under the command of Decker near Kraków and the Jablonka Pass. During the Battle of France, Decker commanded a battalion of the 3rd Panzer regiment in the 2nd Panzer division. This unit fought at the Maas, near Sedan, Saint-Quentin and Abbeville.