To understand how the DMZ has been created, we have to go way back to 1945 when Korea was liberated from Japan.
On August 15, 1945, Japanese Emperor Hirohito announced a surrender message to his people on the national radio. Then, on September 2, Japanese representatives signed the Instrument of Surrender.
Shortly after liberation (August 1945), the 38th parallel was drawn in the middle of the Korean Peninsula as an army boundary by the United States and the Soviet Union. At first, it was intended as a simple military separation line, but in 1948, two independent countries were established, the Republic of Korea in the south and the Democratic People’s Republic of Korea in the north, and the 38th parallel became the border between the two countries.
Then, the Korean War broke out at dawn on June 25, 1950 with a surprise attack by North Korean military forces crossing the 38th parallel. When the North Korean military forces invaded the south, the South Korean troops were not ready at all. There was no equipment or weapons to defend the fully-armed North Korean forces.
It wasn’t until 1953 that the war was over. On July 27, 1953, representatives of United Nations Command, the Korean People’s Army, and the Chinese People’s Volunteer Army met in Panmunjom (판문점)* and signed the armistice agreement. Due to the Korean War, the 38th parallel as a simple border between the two nations disappeared and the armistice line took over.
*Panmunjom (판문점) is the Joint Security Area where the southern half belongs to South Korea and the northern half belongs to North Korea.
Yes, it’s where tourists go when they say they are going on a DMZ tour.