In 1949 communist armies led by Mao Zedong defeated the nationalist regime of Chiang Kai-shek. The communists took control of the Chinese mainland, establishing the People's Republic of China, while Chiang Kai-shek, who had received U.S. support during the conflict, fled to the island of Taiwan. China, previously a loyal U.S. ally and a country Americans felt particularly familiar with because of the strong presence of American Christian missionaries, overnight became one of America's most bitter enemies. With the post–World War II world starkly divided into American and communist spheres of influence, the Chinese shift was seen as a serious loss. From the establishment of the People's Republic of China well into the Korean War and the witch hunts of the McCarthy era, a debate raged in Washington about whom to blame for the loss of...