SEOUL -- The Republic of Korea (ROK) and US forces kicked off their joint annual war game on Monday despite strong backlashes from the Democratic People's Republic of Korea (DPRK).

The annually-held Ulchi Freedom Guardian (UFG) will be conducted from Aug 22 to Sept 2, Combined Forces Command said in a press release.

The computer-assisted simulation exercise will mobilize about 25,000 US troops, including 2,500 reinforcements from the US mainland and the US Pacific Command. It was lower than last year's 30,000 US forces.

From the South Korean side, some 50,000 forces will join the military exercise. It was almost the same as last year's.

The combined forces will reportedly apply Operation Plan 5015 to this year's UFG exercise. The OPLAN 5015 is a wartime joint defense scenario signed in June last year between Seoul and Washington to preemptively destroy the DPRK's nuclear and missile bases in times of military conflicts.

The United Nations Command's military armistice commission notified the DPRK at about 9:40 a.m. local time of the drill schedule and its defense nature verbally in Panmunjom, the truce village in the border dividing the two Koreas.

All of military communications lines between South Korea and the DPRK have been shut down after Pyongyang's nuclear detonation in January and its launch of long-range rocket in February that was seen as a disguised test of ballistic missile technology.

Tensions were heightened further as Seoul and Washington agreed in July to deploy one Terminal High Altitude Area Defense (THAAD) battery in South Korean soil by the end of next year.