South Korea and the United States on Monday began their annual two-week joint war exercise to test and improve their joint defense posture against North Korea, the defense ministry said.



The computer-aided Ulchi Freedom Guardian (UFG) kicked off for a 12-day run, mobilizing some 50,000 South Korean forces and 30,000 U.S. servicemen, including some 3,000 from its homeland and other overseas bases.



With the training expected to include diverse defense drills to curb North Korea's possible provocations, this year will be the first time for the allies to implement their customized deterrence plan against Pyongyang's nuclear threats and weapons of mass destruction, according to the ministry.



The bilateral strategy, drawn up during their defense ministerial meeting last year, delineates how they should work together to deter both wartime and peacetime aggression from Pyongyang, from saber-rattling to the actual use of force.



The drill came amid stronger-than-usual threats from the communist North, though it has long balked at the annual drills and other similar joint maneuvers, claiming they are a prelude to war despite Seoul and Washington's argument that they are defensive in nature.



In a statement issued by an unidentified spokesman for the General Staff of the Korean People's Army on Sunday, the unruly nation vowed to launch "the strongest, most merciless pre-emptive attacks of our own style."



In response, Seoul's defense ministry expressed deep regret, vowing a "merciless counterattack" in case of any provocations.



"During the UFG period, we will further strengthen reconnaissance activities to maintain a tighter defense posture against North Korea," a ministry official said, asking not to be named.



In recent months, North Korea has employed its signature, two-tier strategy of engagement and pressure. In the latest in a series of saber-rattling moves, the North fired five short-range rockets into the East Sea on Thursday, while its leader Kim Jong-un sent a wreath marking the fifth anniversary of the death of South Korea's former President Kim Dae-jung on Sunday.



Along with the war exercise, the South Korean government kicked off a separate four-day emergency exercise earlier in the day.



The annual local drill, involving administrative bodies and public employees nationwide, is designed to examine the government's readiness for dealing with military provocations from the North and potential terrorist attacks.



The Koreas remain technically at war because the 1950-53 Korean War ended in an armistice. About 28,500 U.S. soldiers are stationed in South Korea. (Yonhap)



