However, this practice expended too much valuable ammunition and was of increasingly limited effectiveness as tank armor became thicker.[2] The first dedicated anti-tank artillery began appearing in the 1920s and by World War II was a common appearance in many European armies.[3] In order to penetrate armor they fired specialized ammunition from longer barrels to achieve a higher muzzle velocity than field guns.[4] Most anti-tank guns were developed in the 1930s as improvements in tanks were noted,[5] and nearly every major arms manufacturer produced one type or another.[3]