북방한계선
In August 1953, shortly after the entry into force of the armistice agreement, the South Korean Syngman Rhee Provisional government, which opposed the armistice agreement, attempted to attack the DPRK on the west coast, ignoring the agreement. Accordingly, the United Nations Command set up the "Northern Limit Line" of the West Sea so that the ROK Armed Forces would not attack Hwanghae Island, and this is the starting point of the Northern Limit Line.