Korea was occupied by the US and the USSR after World War II because the peninsula was liberated from Japanese colonial rule in 1945, and the Allied Powers agreed to divide Korea temporarily to accept the Japanese surrender and maintain order. The Soviets occupied the north, and the Americans occupied the south, dividing Korea roughly along the 38th parallel. This division was intended as a temporary administrative measure until a unified, independent Korean government could be established, but it was also influenced by Cold War dynamics and mutual distrust between the US and USSR. The division was proposed by the US to the Soviets shortly after Soviet entry into the war against Japan, with US officers hastily drawing the 38th parallel on a map to define the occupation zones. The Soviets quickly accepted the division. The US aimed to have a zone of control that included the capital, Seoul, while the Soviets controlled the north, where they installed a communist-friendly government. The Americans, fearing Soviet expansion, established a military government in the South with little preparation, often siding with anti- communist factions and suppressing leftist groups. Meanwhile, the Soviets supported local communists in the north, enacting reforms to gain popular support. The occupation ultimately hardened into permanent division as the US and USSR each supported rival governments in their respective zones, leading to the separate states of North and South Korea and eventually the Korean War. The initial agreement to divide Korea was a compromise born from strategic interests and mistrust, rather than a plan for long-term partition. This explanation is drawn from historical sources describing the division and occupation starting in 1945, the military administrations established by the US and USSR, and the resulting political developments that prevented Korean unification after World War II.
