Background

For 200 years, Korea was a “hermit kingdom”, closed off from the outside world and refusing to trade with westerners until the 1880s (Hays, 2021).  This self-imposed policy of isolation caused Korea to lag behind other countries in technology and industry.

Korea was frequently invaded by neighboring countries.  Japan’s designs on Korea in modern times began with the Sino-Japanese War of 1894-1895. Japan defeated China, forced China to give up Formosa (Taiwan) and to recognize Korea (previously a “tributary” state of China) as an independent state (Bisno, 2020).

Russia was building the Trans-Siberian Railway and intended to route it through Manchuria, Chinese territory adjacent to Korea. Russia worried that Japan might try to take over Manchuria. The Russo-Japanese War, won by Japan, was fought over Manchuria and Korea. The Treaty of Portsmouth, signed in 1905, allowed Japan to make Korea a protectorate (history.com editors, 2022; Cumings, 2011, p. xv – xvii).

Japan increasingly dominated Korea and annexed it in 1910, turning it into a colony to supply food and resources to Japan. Japan built factories in Korea. Although there were several growing cities in Korea, the country remained largely agricultural.  The Japanese quickly and brutally put down any petitions for Korean independence (Hays, 2021).

In the 1930s, the Japanese tried to make the Koreans adopt Japanese names and adopt the Shinto religion. In 1938, education in Korean schools was in the Japanese language only (Hays, 2021).  During the Second World War, many Koreans were forced to work in Japan and Korea itself became a labour camp for Japan, with Koreans living under armed guard. Some Koreans were forced to join the Japanese Imperial Army (Hays, 2021).

At the Yalta Conference of 1945, Allied leaders discussed how to reorganize the postwar world. The US and USSR agreed to hold a trusteeship of one half each of Korea after the Japanese were defeated (LeCroix, 2023).  The August 14, 1945 surrender of Japan, following the atomic bombing of Hiroshima and Nagasaki, ended the Second World War.  Soviet troops, at that point part of the Allied forces, entered Korea from the north.  The US was disturbed by this movement and realized that it had to act quickly to prevent Korea from becoming a Soviet state.  The 38th Parallel became the dividing line between the American and Soviet sectors of Korea.  It cut through villages, roads, and railway lines (Johnson and Bowen, 2023). The border had previously been proposed at the Potsdam Conference of July and August 1945. The Korean capital of Seoul, located close to the 38th Parallel, was included in the American sector (history.com editors, 2024). Stalin, leader of the Soviet Union, agreed to these terms.

The Republic of Korea, or South Korea, was established in 1948; the Democratic People’s Republic of Korea (North Korea) was established several weeks after. The intention was for the two parts of Korea to eventually be united, but during the Cold War, the ideological differences between North and South Korea intensified. The Soviet Union set up a Communist government in North Korea under Kim Il-Sung in 1948; an elected, nominally democratic government was established by the US in South Korea in the same year under Syngman Rhee (Granfield, 2004).

When Soviet and American forces pulled out of the Koreas in June 1949, Kim Il-Sung and Syngman Rhee both claimed to be the leader of the entire Korean peninsula, resulting in minor military skirmishes at the border that became increasingly frequent (The Canada History Society, 2025).

In 1950, Kim, the leader of North Korea, suggested to the Soviet Union that South Korea be liberated (invaded).  He received support for the invasion from the Soviet Union and China.  The invasion began on June 25, and took the world by surprise.