YEONCHEON-GUN, SOUTH KOREA – MAY 30: U.S. Army’s M1A2 tank and soldiers from 2nd Battalion, 9th Infantry Regiment of the 1st Armored Brigade Combat Team of 2nd infantry division and South Korean soldiers from 6th Engineer Brigade participate in a river crossing exercise on May 30, 2013 in Yeoncheon-gun, South Korea. The joint exercise is for the first time in 10 years, eyeing possible attacks of North Korea. (Photo by Chung Sung-Jun/Getty Images)