The "loss of China" refers, in U.S. political discourse, to the unexpected Communist Party takeover of mainland China from the American-backed Nationalists in 1949, and therefore the "loss of China to communism". The "loss of China" was portrayed by critics of the Truman Administration as an "avoidable catastrophe". It led to a "rancorous and divisive debate" and the issue was exploited by the Republicans at the polls in 1952. It also played a large role in the rise of Joseph McCarthy, who, with his allies, sought scapegoats for that "loss", targeting notably Owen Lattimore, an influential scholar of Central Asia.
During World War II, Franklin D. Roosevelt had assumed that China, under Chiang Kai-shek’s leadership, would become a great power after the war, along with the U.S., the United Kingdom, and the Soviet Union. According to John Paton Davies Jr. (one of the so-called "China Hands", whose diplomatic career was later ruined by the loss of China), Roosevelt's lack of sufficient material support to Chiang Kai-shek during the war against Japan in the 1930s and 1940s and his deplorable choices of U.S. diplomatic emissaries to China contributed to the failure of Roosevelt's policy.
According to historian Arthur Waldron, "Franklin Roosevelt thought of China as a power already securely held by [Chiang Kai-shek]." Chiang Kai-shek's hold on power was, however, tenuous, and "once the Japanese were defeated, China would become a power vacuum, tempting to Moscow, and beyond the capability of the Nationalists to control. In that sense, the collapse of China into communism was aided by the incompetence of Roosevelt’s policy."