The Battle of Kaesong-Munsan (Hangul:개성, 문산 전투; Hanja:開城 汶山 戰鬪) was a part of Operation Pokpoong, the offensive by the Democratic People's Republic of North Korea that marked the beginning of the Korean War.
Due to the heavy modification of the Republic of Korea Armed Forces, the quality of training of the ROK 1st Infantry Division was extremely lower than that of other divisions. The 11th Infantry Regiment and the 12th Infantry Regiment just began battalion-sized training; only 2 battalions from the 13th Infantry Regiment were at the last phase of the training, and 1 battalion was sent away for the field training.
In addition, 57% of the soldiers were given leave on June 24. Under the circumstances, the 12th Infantry Regiment had to defend 80 km frontline with only 800 troops. Moreover, heavy firearms and vehicles were sent to the rear for reorganization, and the division commander Paik Sun-yup was absent at the scene for training since June 14.