US and South Korean troops kicked off a large-scale exercise Monday aimed at strengthening their combined defense capabilities against North Korea, AP reports. The annual summertime exercise comes amid heightened tensions on the Korean Peninsula The United States and South Korea described their joint drills as defensive in nature and have been expanding and upgrading their training in recent years to cope with the North’s evolving threats. The Ulchi Freedom Shield drills, which continue for 11 days, through August 29, include both computer-simulated war games and more than 40 kinds of field exercises, including live-fire drills. The exercise began hours after North Korea’s Foreign Ministry issued a statement repeating the North’s contention that such exercises are “provocative war drills for aggression.” It said the North’s nuclear ambitions are thus justified, adding that it is crucial to “constantly maintain the balance of power for preventing a war by stockpiling the greatest deterrence.”