During the second World War, the Korean peninsula was a core tenant of the Japanese war machine. Minerals from the region’s mountainous north, like iron, zinc and large reserves of coal, helped fuel the industrial sector of the empire they were conquered by. Meanwhile, the south, with its plentiful rivers and arable land, became the breadbasket for the region, which became acutely important following the Japanese invasions into nearby Chinese territory
Once Japan was defeated by the Allies, however, its future became uncertain. By the end of the war, Soviet troops had already entered Chinese provinces that the Japanese had invaded directly to Korea’s north. In the east, Mao Zedong’s communist forces looked increasingly likely to take hegemony over China from the nationalists, a prospect which western powers were horrified by, seeing as they had just given billions of dollars in aid and material to the latter.
In the United States, there was a very prominent political paranoia around that time regarding a new theory strategists had made up called the “domino theory.” The idea behind this theory was that if one country were to fall to communism, the rest would follow.
The results of the policy could be seen everywhere on the map at the time, whether it be the multitude of Allied and Soviet occupation zones in post-war Germany, the forced deposition of numerous democratically-elected left-leaning leaders in South America, or the soon-to-be borders of Korea.
In August of 1945, the Soviet Union and America decided to create two separate “temporary occupation zones” on the peninsula, just as they had done to Germany after its collapse. In the North, a charismatic self-proclaimed “war hero,” Kim Ill Sung, had been appointed leader of the new communist regime. In the South, Korean exile-government Syngman Rhee won an election in 1948 to lead their new country. Despite being democratically elected, however, make no mistake, Rhee was a ruthless autocrat. He was not as bad as Kim Ill Sung, who introduced “reeducation” campaigns and a forced collectivization system, but he did not exactly advocate for freedom of the press.
Shortly after Rhee’s ascension into office, elections for the next South Korean president were indefinitely postponed, as Rhee would continually declare martial law, citing the communist regime in the north to quash unrest and student protests.
In the North, the country’s vast mineral wealth led to rapid industrialization, and aid from the Soviet Union only helped bolster their economy further. This would lead Kim to believe that now was the time to strike. The South, in comparison, was in complete disarray and their military was incredibly disorganized.
In June of 1950, the North declared war on the South, with communists blasting through the poorly-defended lines of the adversaries, making rapid progress until finally being stalled at the city of Pusan. By this point, North Korea had held more than seventy percent of the South’s territory as well as the country’s capital, Seoul. The United States, suddenly seeing all of this unfold, rapidly passed provisions within the U.N’s Security Council to send American troops overseas to the peninsula in just under forty-eight hours.
The importance and speed of this intervention cannot be understated. In a matter of months, a joint force composed of America and its allies led a U.N. force to almost entirely reverse the course of the war. North Korean units quickly found themselves overwhelmed and over-stretched, causing them to abandon many key positions, including Pusan. This allowed U.N. troops to eventually take Pyongyang, the North’s capital. North Korean armies were forced to fall back behind the expansive mountain range that had been such an essential boon to them a handful of years prior.
China had now become just as paranoid about a capitalist republic on its borders, just as the Americans had become paranoid of communist expansion in 1950, leading the former to unleash an onslaught of hundreds of thousands of reservists from its own hard-fought civil war to stem the bleeding using wave tactics. These troops, while poorly equipped, proved highly effective, due in large part to their sheer magnitude in numbers when compared to their foes.
By the signing of the armistice in 1953, both sides had stabilized along the 49th Parallel for a little over a year, leading to both sides determining that the status quo would not change without a significant upset. These events led to the creation of the Demilitarized Zone, which is still in effect today.