Improved artillery was seen as the quickest solution to anti-tank defense, and one of the earliest post-war anti-tank gun designs was the 25 mm Hotchkiss model from France. It was intended to replace an Atelier de Puteaux 37 mm weapon designed in 1916 to destroy machine gun positions. Rheinmetall commenced design of a 37 mm anti-tank gun in 1924 and the first guns were produced in 1928 as 3.7 cm Pak L/45, later adopted in Wehrmacht service as 3.7 cm Pak 36. It made an appearance during the Spanish Civil War, as did the Bofors 37 mm developed in Sweden, and used by many early Second World War combatants. The British Army accepted for service the (40 mm) Ordnance QF 2 pounder, which was developed as a tank gun. The Soviet Red Army after the also begun a search for an anti-tank gun with a French Hotchkiss 37 mm L.33 tank gun, but soon upgraded this to a higher velocity L.45 Model 1935 while also making a licensed copy of the German 3.7 cm PaK 36. However, the Red Army was almost immediately taught a lesson about anti-tank warfare when a tank battalion sent to aid the Spanish Republicans in the Spanish Civil War was almost entirely destroyed in an engagement.