South Korean and US troops have began large-scale joint military exercise today. The exercise is to test their defense readiness against the threat from North Korea, which routinely characterizes the drills as preparation for war against it. <br/><br/>The exercise comes amid heightened tension following the latest test launch of a ballistic missile by the North on 12th of last month. South Korea's Defense Ministry and the U.S. military based in the South confirmed the start of the drills and said that it will continue until the end of April.<br/><br/>Meanwhile, North Korea's official KCNA news agency said its leader Kim Jong Un inspected the headquarters of a major military unit and issued guidance on increasing combat readiness.