Vietnamese Demilitarized Zone The Vietnamese Demilitarized Zone was established as a dividing line between North and South Vietnam as a result of the First Indochina War . During the Second Indochina War ( popularly known as the Vietnam War ) , it became important as the battleground demarcation separating North Vietnamese territory from South Vietnamese territory . Geography . The Vietnamese Demilitarized Zone ran from east - west near the center of present - day Vietnam ( spanning more than a hundred kilometers ) and was a couple of kilometers wide . It ran along the Ben Hai River for much of its length , and an island nearby was controlled by North Vietnamese forces during the Vietnam War . Although it was nominally described as being at " the 17th parallel , " almost all of the zone lies to the south of the parallel , with only a small portion of the zone near the eastern shore actually including the parallel . It was around a hundred kilometers north of the city of Huế . The First Indochina War . The First Indochina War ( also called the French Indochina War ) was fought in French Indochina from 1946 through 1954 between France and the French - controlled State of Vietnam on the one side , and the Communist - dominated independence movement , the Viet Minh , on the other . The Viet Minh won the war , gaining effective control of all northern Vietnam except an enclave around Hanoi . In 1954 , France gave up its control of Vietnam , and the Viet Minh was recognized as the government of northern Vietnam . Establishing the DMZ . The post - colonial conditions of Vietnam were set at the Geneva Conference of 1954 ; the agreement was finalized on July 21 , 1954 . The Geneva agreement reflected the military results at that time . The northern part of Vietnam , which was almost entirely controlled by the Viet Minh became the Democratic Republic of Vietnam , under Communist leader Ho Chi Minh . The southern part of Vietnam , where the Viet Minh controlled relatively small and remote areas , became the independent State of Vietnam under Bảo Đại , the last scion of the old Vietnamese imperial house . The State of Vietnam later became the Republic of Vietnam . 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 . The area within 5 km on either side of the border was declared to be a demilitarized zone . Troops of both governments were barred from this area . Tourism . Exploring the Demilitarized Zone can today be comfortably achieved by joining one of various organised tours starting daily from Hué . Together with a local guide the most famous war settings , as Khe Sanh Combat Base , The Rockpile , Ho - Chi - Minh - Trail , Doc - Mieu - Station or the Vinh Moc tunnels are visited on a full - day trip . On the way from Doc - Mieu to Vinh Moc on the route 1A , you ' re crossing Ben Hai River next to a bridge that was frequently bombed during the Vietnam War , but which still exists today . Although the Vietnam War ended decades ago , walking outside marked tracks can still be dangerous because of numerous unexploded ordnance devices .