While tank destroyers had proven their versatility and efficiency in combat, especially in secondary roles, their long-term utility was becoming doubtful by 1945 in light of changes to Army doctrine. Their primary role was to destroy enemy armor, but this role was being usurped by tanks, as had already happened in many other armies. The most powerful tank destroyer to be fielded, the M36, mounted a 90 mm gun; the same armament was carried by the M26 Pershing heavy tank, which was beginning to reach front-line units by the end of hostilities. The M26 was redesignated as a medium tank shortly after the end of the war, becoming the standard vehicle of armored units, and further reducing the need for any specialist anti-tank capacity. In effect, tank destroyers were used just like tanks in many cases. Study of ammunition expenditures shows that tank destroyers in Europe fired about 11 rounds of high-explosive (HE) ammunition for every round of armor-piercing (AP) ammunition, showing that they were used for general support duties far more often than as anti-tank assets.