The Vietnamese Demilitarized Zone was established as a dividing line between North and South Vietnam as a result of the First Indochina War. The boundary between these two zones was established at the Ben Hai River, which enters the South China Sea at 17 degrees 0 minutes 54 seconds N latitude. The boundary followed the Ben Hai to its headwaters, about 55 km WSW, and thence to the Laotian border.