3 . 7 cm Pak 36 The Pak 36 ( " Panzerabwehrkanone 36 " ) was a German anti - tank gun that fired a 3 . 7 cm calibre shell . It was the main anti - tank weapon of Wehrmacht infantry units until 1942 . It was followed in this role by 5 cm Pak 38 gun . History . Design of a horse - drawn , 3 . 7 cm anti - tank gun ( designated 3 . 7 cm Pak L / 45 ) by Rheinmetall commenced in 1924 and the first guns were issued in 1928 . By the early 1930s , it was apparent that horse - drawn artillery was obsolescent , and the gun was modified for motorized transport by substituting magnesium - alloy wheels and pneumatic tyres for the original spoked wooden wheels . Re - designated the 3 . 7 cm Pak 35 / 36 , it began to replace the 3 . 7 Pak L / 45 in 1934 and first appeared in combat in 1936 during the Spanish Civil War . It formed the basis for many other nations ' anti - tank guns during the first years of World War II . The KwK 36 L / 45 was the same gun but was used as the main armament on several tanks , most notably the early models of the Panzer III . Even the Soviets used the PaK 36 carriage design for their 45mm M1937 AT gun . Operational history . During May 1940 Western Campaign , the Pak 36 being a small - calibre weapon , it was found to be inadequate against allied tanks like the British Mk . II Matilda , and the French Char B1 and Somua S35 . Still , the gun was effective against the most common light tanks , such as the Renault FT - 17 during the Battle of France , where the Char Bs and Matildas represented but a small fraction of the total AFVs . In June 1941 , the Soviet forces consisted of 10 , 661 T - 26s , 2 , 987 T - 37 / 38 / 40 / 50s , 59 T - 35s , 442 T - 28s , 7 , 659 BTs , 957 T - 34s , and 530 KVs for a combined total of approximately 23 , 295 tanks . Thus , during the initial phases of Operation Barbarossa the Pak 36 could still penetrate the majority of Soviet AFVs at ranges up to 1000m from the front , with the notable exception of the T - 28s and T - 35s which it could only penetrate at under 100m . Here the Pak 36 only had difficulty with the T - 34s and KVs which it could not penetrate . By late 1941 , however , the widespread introduction of medium tanks quickly erased the gun ' s effectiveness ; miserable performance against the T - 34 on the Eastern Front led to the Pak 36 being nicknamed " Heeresanklopfgerät " ( literally " army door - knocking device " ) , for its inability to produce any effect on the T - 34 aside from notifying the tank of its presence by futilely bouncing rounds off its armor ( regardless of the angle or distance ) . The Pak 36 began to be replaced by the new 5 cm Pak 38 in mid - 1940 . The addition of tungsten - core shells ( " Pzgr . 40 " ) added slightly to the armour penetration of the Pak 36 . Despite its continued impotence against the T - 34 , it remained the standard anti - tank weapon for many units until 1942 . With tungsten core rounds , the Pak 36 crews could finally achieve kills on T - 34s , but only via direct shot to the rear or side armour from point - blank range , an unlikely and rather suicidal scenario . The advantages of the Pak 36 were its ease of handling and mobility where it could be brought into action very rapidly by as little as two men ( it weighed only 432 kg ) , its good quality optical aiming devices , that it was small and easy to conceal , and that it had a very high rate of fire . As the Pak 36 was gradually replaced , many were removed from their carriages and added to SdKfz 251 halftracks to be used as light anti - armour support . The guns were also passed off to the forces of Germany ' s allies fighting on the Eastern Front , such as the 3rd and 4th Romanian Army . This proved particularly disastrous during the Soviet encirclement ( Operation Uranus ) at the Battle of Stalingrad when the Romanian forces , already demoralized and understrength , bore the brunt of the main Soviet armored thrust , and were unable to stop the Soviet advances due to their grossly inadequate anti - tank weaponry . The Pak 36 also served with the armies of Finland ( notably during the battle of Suomussalmi ) , Hungary , and Slovakia . Although the PaK 36 was generally ineffectual in Europe , it became a real tank - killer in China . A PaK 36 could destroy the Japanese Type 95 Ha - Go and Type 97 Chi - Ha tanks , since their armor protection was quite weak . For example , during the Battle of Taierzhuang , the Chinese PaK 36 destroyed 13 Japanese tanks . This made the Chinese soldiers so excited , and the Japanese soldiers so shocked , that the battle was stopped for several minutes . This was tungsten cored ammunition , lighter and with higher muzzle velocity , produced in small quantities . 37mm Pak 36 L / 45 ammunition . Penetration figures given for Pzgr 40 and an armoured plate 30 degrees from the horizontal . Stielgranate 41 . In 1943 , the introduction of the Stielgranate 41 shaped charge meant that the Pak 36 could now penetrate any armour , although the low velocity of the projectile limited its range . The Pak 36s , together with the new shaped charges , were issued to Fallschirmjäger units and other light troops . The gun ' s low weight meant that it could be easily moved by hand , and this mobility made it ideal for their purpose .