The South Korea and US militaries have commenced the annual Ulchi Freedom Guardian exercise that will continue through Sept. 2, the Combined Forces Command said Monday.

A total of 50,000 South Korean troops and 25,000 US troops are taking part in the exercise, with about 2,500 US soldiers coming from off the peninsula.

The nine UN states participating in the drill include Australia, Canada, Colombia, Denmark, France, Italy, the Philippines, the UK and New Zealand. Switzerland and Sweden will monitor the exercise as Neutral Nations Supervisory Commission observers to ensure that it is in compliance with the 1953 armistice agreement that ceased the 1950-53 Korean War.

As of 9:40 a.m., the UN Command Military Armistice Commission informed the North Korean army of the drill and its non-provocative nature, via North Korean soldiers stationed at the inter-Korean truce village of Panmunjom.

Ulchi drill, named after legendary Korean Gen. Eulji Mun-deok, is a command post exercise carried out every August.

“The UFG is designed to enhance (Seoul-Washington) alliance readiness, protect the region and maintain stability on the Korean Peninsula,” the CFC said, adding that the drill is based on the armistice treatment and the 1953 mutual defense treaty by South Korea and the US.

Conducted in the form of a computer-simulated war game, its history dates back to 1976 when the Seoul government’s Ulchi drills -- which started in 1968 -- were merged with the UN command-led Focus Lens exercise to form the “Ulchi Focus Lens.” It was later renamed to the UFG in 2008.

In addition to the war games, the government and related agencies also carry out exercise related to actions to take during wartime, including civilian evacuation and countermeasures to biological and terrorist attacks. A total of 480,000 from some 4,000 public and civil groups participate.

The North has been stepping up nuclear and ballistic missile threats against the allies, with a nuclear test and long-range rocket launch earlier in the year. The UN Security Council subsequently passed a resolution 2270 that encompassed the strongest economic sanctions against Pyongyang to date.

The Seoul government is expecting North Korea to carry out some form of provocative action around the time of the drills.

On Sunday, the Unification Ministry said that the UN sanctions has put the North in a “very difficult spot,” and that it may attempt to provoke South Korea during the UFG to rally its citizens’ support behind the Kim Jong-un regime.

The hermit kingdom on Monday blasted the annual drills as a “phased scheme for invasion,” and threatened to launch a pre-emptive nuclear strike “upon the slightest sign of invasion.”

President Park Geun-hye presided over a National Security Council meeting Monday and ordered vigilance against Pyongyang.

“North Korea has been blatantly mentioning the possibility of its provocations, threatening that there is no telling what results the UFG may bring upon the Korean Peninsula,” said President Park Geun-hye. “Since the chance of the North’s provocation is higher than ever, and nuclear and missiles are a direct and realistic threat, we have to ensure that our corresponding drills are executed just like in actual battle.”

According to the government, some of the actions Pyongyang might take include an attack against high-profile North Korean defectors, kidnapping South Korean citizens and officials outside the country, and assassination against anti-Pyongyang activists and cyberterrorism.

Last week, North Korea released a statement that branded the recently-defected former North Korean diplomat Thae Yong-ho as a traitor, accusing him of embezzlement of state funds, sex crime against a minor and leaking the nation’s secrets.

With inter-Korea tension growing, the allies’ joint drills appeared to take a more offense-oriented approach toward the North.

This year marked the first time the allies carried out operation plan 5015, which stipulates pre-emptive precision strikes against the Kim Jong-un regime and its nuclear and missile facilities. It was signed last June to replace OPLAN 5027, a scenario based on a counterattack against the North and a war.

As part of the UFG, the South Korean Air Force is also conducting the large-scale Soaring Eagle aerial exercise, a week-long drill from Aug.19-26.

According to the Air Force, the drill will include defensive counter-air attacks against enemy fighters, strikes against the enemy’s key facilities and the source of attack, along with experimental airborne alert interdiction that will take out ballistic missile threats.

By Yoon Min-sik (minsikyoon@heraldcorp.com)