At the beginning of the WWII on 01 September 1939 the Wehrmacht was equipped with 11.200 anti-tank guns 3,7 cm Pak 35/36 that could effectively fight Polish and Soviet light tanks of the early period with their light anti bullet armor, however it couldn't penetrate medium tanks such as British Matilda and Russian T-34 and KVs which resulted in the nickname Door Knocker by the Germans. The Pak 35/36 was used on all fronts during WWII, proven by the fact that in March 1945 the Wehrmacht had still 216 units of this gun in combat service with other 670 guns stored in arsenals.