In 1950 the Korea Peninsula was divided between a Soviet-backed government in the north and an American-backed government in the south. The division of Korea into two halves had come at the end of World War II. In August of 1945 the Soviet Union invaded Korea, which had been under Japan's control since 1910. Fearing that the Soviets intended to seize the entire peninsula from their position in the north, the United States quickly moved its own troops into southern Korea. Japanese troops surrendered to the Russians in the north and to the Americans in the south.
It was primarily the "b. formation of the Vietcong in Vietnam" that led the Truman administration to expand the containment doctrine to include Asia, since this was seen as a threat to democratic principles in the west as well.
