1949年前国民党腐败，土共土改和不遗余力的抗日得到民心。
土共得到民众的支持有着高超的军事技巧和士气 赢得中国政权。
原文美国国务院，历史里程碑： 1945-1952 中国革命
（https://history.state.gov/milestones/1945-1952/chinese-rev）

During World War II, popular support for the Communists increased. U.S. officials
in China reported a dictatorial suppression of dissent in Nationalist-controlled
areas. These undemocratic polices combined with wartime corruption made the
Republic of China Government vulnerable to the Communist threat. The CCP, for
its part, experienced success in its early efforts at land reform and was lauded
by peasants for its unflagging efforts to fight against the Japanese invaders.

As the civil war gained strength from 1947 to 1949, eventual Communist victory
seemed more and more likely. Although the Communists did not hold any major
cities after World War II, they had strong grassroots support, superior military
organization and morale, and large stocks of weapons seized from Japanese
supplies in Manchuria. Years of corruption and mismanagement had eroded popular
support for the Nationalist Government. Early in 1947, the ROC Government was
already looking to the island province of Taiwan, off the coast of Fujian
Province, as a potential point of retreat. Although officials in the Truman
Administration were not convinced of the strategic importance to the United
States of maintaining relations with Nationalist China, no one in the U.S.
Government wanted to be charged with facilitating the “loss” of China to
communism. Military and financial aid to the floundering Nationalists continued,
though not at the level that Chiang Kai-shek would have liked. In October of
1949, after a string of military victories, Mao Zedong proclaimed the
establishment of the PRC; Chiang and his forces fled to Taiwan to regroup and
plan for their efforts to retake the mainland