The Korean War was the result of tension breaking between Soviet backed North Korea and South Korea. It started with Kim Il-Sung believing that South Korea would welcome an invasion by the Soviets, and asking Stalin for help with his invasion. Stalin was quick to give the OK and an army to help take over. Over the course of the initial push by North Korea, almost all of South Korea was taken over. The UN quickly jumped in though and pushed back, taking over most of North Korea, with the US supplying most of the men to the war. After some long and hard debates, an agreement was reached, where both countries kept their old borders and would not attack each other, with the UN monitoring the armistice.