As a young artillery lieutenant ("Leutnant der Artillerie") in Panzer Group Kleist, Siegfried Knappe participated in the Invasion of France. Knappe was decorated for actions that took place on the night of 14 June 1940. The actions took place in the Paris area, south of Tremblay-en-France, at the Ourcq canal. A group of French sailors had apparently not been informed of the decision to declare Paris an open city. As a result, they were defending a bridge with machine guns from a house across the canal. After German infantry failed to clear the area with mortar fire, artillery support was requested.