Back in 1944, even while World War II was far from over, American leaders already recognized that the next major confrontation would pit the United States against the Soviet Union. Once the post-war dust settled, this rivalry crystallized into what the world came to call the Cold War — a prolonged era of tension, saber-rattling, and arms races between the planet's two dominant superpowers. Although the US and USSR never directly waged open war against one another, they repeatedly clashed through so-called 'proxy wars.' The earliest of these erupted on June 25, 1950, when North Korean forces surged across the border into South Korea, sparking the Korean War.
Ever since its controversial annexation in 1910, Korea had been absorbed into the Japanese Empire. When Japan finally surrendered to the Allies in 1945, a pressing question emerged: what should become of its former imperial holdings? The Korean people, for their part, had no desire to remain under imperial domination. In a move reminiscent of how Berlin was partitioned, the Allies split the Korean peninsula at the 38th parallel. The northern half fell under Soviet administration, while the United States assumed control of the south.
Both superpowers wasted no time molding their respective zones in their own image. In the south, the United States threw its weight behind Syngman Rhee, a capitalist dictator, while the Soviets championed Kim Il Sung, the communist leader who would go on to found the Kim dynasty. Clashes along the border became routine, fueled by both leaders' conviction that they alone deserved to govern all of Korea. Still, the international community was stunned when Kim launched an invasion force of 75,000 soldiers — backed by Soviet Russia and Maoist China — across the border into South Korea.
The invasion sent shockwaves through the corridors of power worldwide. Many leaders interpreted it as the Soviet Union's opening gambit in a campaign to spread Communism around the globe. If Korea succumbed, certain politicians warned, the rest of Asia — and eventually the entire world — could follow. Stepping in to stop it became, in essence, a political imperative.
Just two days after the invasion began, President Harry S Truman authorized a "police action" in South Korea. What followed over the next three years ranks among the bloodiest and most devastating wars ever fought on Asian soil. While the United States would lose around 55,000 soldiers in the conflict, total fatalities are estimated to be between two to three million. At least half of those killed are presumed to have been civilians trapped in the crossfire, and nearly every Korean city endured severe damage throughout the war.
The momentum of the conflict shifted decisively after General Douglas MacArthur captured the port city of Inch'on. In July 1953, the warring sides put their signatures on an Armistice Agreement. This treaty silenced the guns but did not formally end the war. To this day, both North Korea and South Korea consider themselves to still be at war with each other, and the Demilitarized Zone straddling the 38th parallel stands as one of the most heavily surveilled places on the planet. That said, recent years have seen South Korea agree to work with China toward bringing official peace between the two nations.