As Yoon suggested, great-power politics is the reason Korea was carved up in the first place. One August night in 1945, near the end of World War II, two young American Army colonels with nothing but a National Geographic map came up with a way to cede northern Korea to the Soviet Union and southern Korea to the United States for the purposes of accepting Japan’s sudden surrender. The goal was to prevent the Russians from overrunning Korea before the Americans could establish a presence on the peninsula, which had been unified for centuries but dominated by Japan since the end of the Russo-Japanese War in 1905.
The officers, Dean Rusk and Charles Bonesteel, didn’t know much about Korea, but they did recognize that any partition should include the capital city of Seoul in the American zone of occupation. So they split the peninsula along the circle of latitude known as the 38th parallel, just north of Seoul and roughly in the middle of the peninsula. Their superiors quickly agreed to the proposal, as did the Soviets. Millions of Koreans, who had little say in the arbitrary separation of their people and provinces and waterways and highways, watched as their Japanese rulers were replaced by American and Soviet ones. Today Korea evokes the world’s most volatile conflict; back then, in the wake of a world-shattering war, it was something of an afterthought.
The 38th parallel was initially intended as a temporary division of liberated land among wartime allies—a joint trusteeship that would be replaced by a unified, independent Korea once the postwar chaos ebbed. But it instead hardened into a marker of rival spheres of influence among Cold War enemies, as the South held elections and the North founded the undemocratic Democratic People’s Republic of Korea. In 1950, Kim Il Sung, the leader of the DPRK, crossed the 38th parallel and invaded the Republic of Korea, sparking a war in which Russia and China sided with North Korea and America sided with South Korea. (The armistice ending the conflict shifted the border a bit from the 38th parallel to the Demilitarized Zone. As fate would have it, Rusk and Bonesteel later became lead actors in the drama they designed, serving as the secretary of state and the commander of U.S. forces in South Korea, respectively, during a series of North Korean attacks in the late 1960s; Rusk was also a vocal advocate of U.S. involvement in the Korean War.)
Korean leaders have charted their own divergent paths ever since, with the South evolving into a flourishing capitalist democracy and the North into a totalitarian fortress state. But their superpower patrons have accompanied them along the way.
The current crisis, for example, is largely the result of Kim Jong Un rapidly developing his nuclear and missile arsenal with one provocative test after another, just as the Korean War was sparked by Kim Jong Un’s grandfather launching a massive military offensive against the South. Yet it has morphed into an international test of wills among the world’s major powers, with America pressuring Russia and China—at the United Nations Security Council, at Trump-Xi Mar-a-Lago meetings and on Trump-Putin phone calls—to impose more severe sanctions on North Korea.