Lee Jae-Won / Reuters
Amphibious assault vehicles of the South Korean Marine Corps launch smoke bombs as they move to shore during a U.S.-South Korea joint landing operation drill in Pohang, about 230 miles southeast of Seoul, on April 26, 2013. The drill is part of the two countries' annual military training called Foal Eagle, which began on March 1 and runs until April 30.
Tension has been fueled by North Korean anger over the imposition of U.N. sanctions after its last nuclear arms test in February. The two Koreas have been technically in a state of war since a truce that ended their conflict, which lasted from 1950 to 1953.