U.S. Army and Republic of Korea Army soldiers guard the border at the Demilitarized Zone in the Republic of Korea, Nov.1, 2015. U.S. Defense Secretary Ash Carter is visiting the Asia-Pacific region, where he will meet with leaders from more than a dozen nations to help advance the next phase of the U.S. military’s rebalance in the region by modernizing longtime alliances and building new partnerships. Photo by Air Force Senior Master Sgt. Adrian Cadiz