After World War II, Korea was split in two with the north occupied by the Soviets and the south occupied by the Americans and their allies. In 1950, the north invaded the south to try to unify the country. During the war, the north was supported by China and the Soviet Union, while the south was supported by troops from the United States. The US and Russia weren’t fighting directly, but through Korean proxies. After 3 years of fighting and millions killed, the war ended in a stalemate.