An anti-tank gun is a form of artillery designed to destroy tanks and other armoured fighting vehicles, normally from a static defensive position. The development of specialized anti-tank munitions and anti-tank guns was prompted by the appearance of tanks during World War I. To destroy hostile tanks, artillerymen often used field guns depressed to fire directly at their targets, but this practice expended too much valuable ammunition and was of increasingly limited effectiveness as tank armor became thicker. The first dedicated anti-tank artillery began appearing in the 1920s, and by World War II was a common appearance in many European armies. To penetrate armor, they fired specialized ammunition from longer barrels to achieve a higher muzzle velocity than field guns. Most anti-tank guns were developed in the 1930s as improvements in tanks were noted, and nearly every major arms manufacturer produced one type or another. Anti-tank guns deployed during World War II were often manned by specialist infantry rather than artillery crews, and issued to light infantry units accordingly. The anti-tank guns of the 1920s and 1930s were of small caliber; nearly all major armies possessing them used 37 mm ammunition (the British Army used the slightly larger 40mm 2-pounder gun). As World War II progressed, the appearance of heavier tanks rendered these weapons obsolete, and anti-tank guns likewise began firing larger and more effective armor-piercing shot. The development of the compact hollow charge projectile permanently altered anti-tank warfare, since this type of ammunition did not depend on a high muzzle velocity and could be fired from low-recoil, man-portable light weapons, such as the Panzerfaust and the American series of recoilless rifles. Although several large-caliber guns were developed during the war that were capable of knocking out the most heavily armored tanks, they proved expensive and difficult to conceal. The later generation of low-recoil anti-tank weapons, which allowed projectiles the size of an artillery shell to be fired from the shoulder, was considered a far more viable option for arming infantry. Recoilless rifles replaced most conventional anti-tank guns in the postwar period; nevertheless, the development of new anti-tank guns exhibiting similar low-recoil performance continued until the late 1950s in France, Belgium, and the Soviet Union. A few Soviet designs saw combat well into the 1980s. The People's Republic of China was still producing large-caliber anti-tank guns as late as 1988. In the 2000s, armies have increasingly preferred guided anti-tank missiles