The United States was concerned that the Soviet Union would spread their influence and communism. So the United States proposed that the Soviet Union Occupy the north and the United States will occupy the south to help rebuild the country and then leave them to decide which government they want to themselves. Obviously the north wanted Communism and the south wanted a democracy. Interestingly, although fighting has stopped the North Korea and South Korea are technically still at war and are still upholding their armistice agreement.