<Li> October 2: United Nations forces cross the 38th parallel, into North Korea . </Li> <Li> October 5: Forces from the People's Republic of China mobilize along the Yalu River . </Li> <Li> October 22: Pyongyang, the capital of North Korea, falls to United Nations forces . </Li> <Li> October 22: China intervenes in Korea with 300,000 soldiers, catching the United Nations by surprise . However, they withdraw after initial engagements . </Li>

What were the events that led up to and marked the beginning phases of the cold war