South Korea and the United States today began anti-submarine drills in the Yellow Sea, the latest in a series of planned show of joint military prowess. The five-day joint naval exercises, the second by Seoul and Washington will involve about ten ships including two U.S. destroyers, submarines, patrol planes and some 1,700 troops from both sides. South Korea and the United States jointly staged massive naval exercises in late July, and are planning on another round of drills in late October.