This doctrine failed on the European battlefield where attacking American tanks ran into defending German tanks and self-propelled guns far more often than intended, and the tank destroyers were called in to assist. Tank destroyers were often deployed to attack enemy armor at long range from an ambush position. During the battle for Italy, tank destroyers compensated for a shortage of 155 mm artillery ammunition by using their 3-inch or 76 mm guns in indirect fire role. Near the end of the war, there were so few German tanks that tank destroyers were increasingly used as self-propelled artillery in support of infantry for lack of any other targets. In effect, they were used exactly like tanks.