Tanks in the Cold War Korean War M24 Chaffee's were the first U.S. tanks to fight the North Korean T-34-85s. The Chaffee fared poorly against these much better-armed and armored medium tanks. Chaffees were more successful later in the war in their reconnaissance role, supported by heavier tanks such as the M4 Sherman, M26 Pershing, and M46 Patton. The heavier but older Pershing was deemed unsatisfactory due to its inferior mobility, which was unsuitable for a medium tank role as it used the same engine that powered the much lighter M4 Sherman, and 1949, the upgraded M26 received a new power plant and a main
Opposition to the war in Afghanistan (2001–2014) entering an eleventh year on October 7, 2011 and marking for the U.S. the longest period of sustained warfare in its history – greater than the time the United States was involved in World War I, World War II and the Korean War combined.<ref name="War and Sacrifice in the Post-9/11 Era"></ref> The war in Afghanistan surpassed the length of official U.S. participation in the Vietnam War, 8 years and 5 months, in the spring of 2010 to become the longest-running U.S. war ever. According to a study by the RAND Corporation, an American think tank working for the U.S. military,