YEONCHEON-GUN, SOUTH KOREA - MAY 30:  US 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)