Anti-tank gun
An anti-tank gun is a form of artillery designed to destroy tanks and other armored 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.