Short answers, pulled from the story.
The Chinese Civil War started in 1927 and ended in 1949. The conflict began with a split between the Kuomintang and Communist Party in early 1927 and concluded when Mao Zedong officially proclaimed the People Republic of China on the 1st of October 1949.
Mao Zedong became chairman of the Military Commission while Zhou Enlai served as vice-chairman during the Long March. This shift occurred in November 1935 after the First Front Army escaped annihilation by Chiang Kai-shek's troops.
More than 130,000 KMT defenders died during the Taiyuan Campaign which lasted more than six months. The battle ended on the 24th of April 1949 when PLA occupied Shanxi Governor Mansion and wiped out all remaining defenders.
Between 90,000 to 100,000 people began the Long March from Soviet Chinese Republic but only around 7,000 to 8,000 made it to Shaanxi. The massive military retreat covered approximately 12,500 kilometers or 25,000 li over a period of 370 days.
US President Harry S Truman announced the 5th of January 1950 that the United States would not intervene in an attack on the People Republic of China. However the Korean War onset in June 1950 led Truman to order the Seventh Fleet to sail into the Taiwan Strait for containment purposes.