South Korea and the United States will start on Sunday another round of joint naval drills off the west coast of the Korean peninsula. The five-day anti-submarine exercises will be held in waters near the tense maritime border between the two Koreas as part of the latest response to North Korea's alleged torpedo attack on a South Korean warship in March. About ten vessels, including USS Curtis Wilbur and USS Fitzgerald, will be mobilized for the latest round of drills that military officials said are meant to send a clear message of deterrence to Pyongyang. In July, the two allies held massive naval and air exercises together in waters east of the divided peninsula, which involved 20 ships and submarines, 200 aircraft and some 8,000 troops.