The dam was proposed by Sun Yat-sen, a Chinese political leader, in 1919. The site was surveyed in 1932 and 1939, by the Chinese and Japanese respectively. The Japanese drew up a plan (the Otani plan) for the dam, only to realize later that China would remain under Chinese control. Later, in 1944, the United States helped make plans for the dam, but all work on the dam stopped in 1947, because of the Chinese Civil War. In 1949, work resumed, but the work was slow because of problems in the economy. Later in 1958, some engineers who were against the dam were put in jail.