Before World War II had started until the end of the war, Korea was under the control of the Japanese. The United States and the Soviet Union declared war on Japan in 1941. The United States entered Korea from the South while the Soviet Union entered from the North. After fighting, the Japanese surrendered on August 10, 1945. The Soviet Union and the United States agreed to divide Korea into North and South Korea. The Japanese that were in North Korea would surrender to the Soviet Union. The Japanese that were in South Korea would surrender to the United States. North Korea and South Korea set up their own government. Eventually, both sides were intent on reuniting Korea as a whole. However both South Korea and North Korea wanted to reunite their own way. North Korea had a strong military and big support from the Soviet Union. South Korea had a small military with only a little support from the United States.   North Korea knew that if they invade South Korea, they would be able to conquer them and reunite Korea their own way, setting up their way of government and life. With this idea in mind, North Korea chose the way of war and their means to reunite Korea under their control.