The deterioration of relations between China and Soviet Union disrupted subway planning. Soviet experts began to leave in 1960, and were completely withdrawn by 1963. In 1961, the entire project was halted temporarily due to severe hardships caused by the Great Leap Forward. Eventually, planning work resumed. The route of the initial line was shifted westward to create an underground conduit to move personnel from the heart of the capital to the Western Hills. On February 4, 1965, Chairman Mao Zedong personally approved the project.