The Pershing was a heavy tank of the United States Army. It was designated a heavy tank when it was first designed in World War II due to its 90mm gun, and its armor. In 1957, the U.S. developed the M103 tank, which had an even larger 120mm gun, and the M26 Pershing was re-designated as a medium tank. The tank is named after General John J. Pershing who led the American Expeditionary Force in Europe in World War I. It was briefly used both in World War II and the Korean War.