 The nuclear forces were operated by the 100,000-person Strategic Missile Force, which was controlled directly by the Joint staff.China began developing nuclear weapons in the late 1950s with substantial Soviet assistance.With the Sino-Soviet split in the late 1950s and early 1960s, the Soviet Union withheld plans and data for an atomic bomb, abrogated the agreement on transferring defense and nuclear technology, and began the withdrawal of Soviet advisers in 1960.