other tough Asian problems. It was not until 1969 and 1971 that Moscow solicited American approval of a preemptive strike against Chinese nuclear facilities, and not until 1972 that Brezhnev hinted at a swap of suspension of Soviet aid to Hanoi for American approval of Soviet preemption of China's nuclear program, but Mao was probably already imagining such possible superpower partnerships. China, in its isolated international situation, would have little diplomatic leverage to block any resultant projects which might be directed against it.31
Partial disengagement from Vietnam also increased China's ability to cope with this deepening superpower "collusion." In Chinese vernacular, this was known as "grasping the contradictions" between the superpowers. Continuing heavy Chinese engagement as the Vietnam War entered a new, more conventional stage would make it difficult for Beijing to improve relations with Washington in order to thwart Moscow's anti-Chinese schemes. Continued deep Chinese involvement might also facilitate Soviet schemes to maneuver the United States into support of various anti-China projects. Partial disengagement, on the other hand, would lessen the likelihood that China would have to face the mounting threat from the north while simultaneously involved in a military confrontation with the United States to the south. Partial disengagement would also clear the way for Chinese efforts to maneuver the United States into opposition to Moscow's anti-China schemes. In a way, China's withdrawal of its forces from North Vietnam in 1968-1970 was a counterpart of the U.S. withdrawal from South Vietnam during 1969-1973. Both helped open the door to Sino- American rapprochement.
Mao Zedong and Zhou Enlai decided to partially disengage China from Vietnam in 1968 because they believed that China was loosing control over events there in an international situation that was increasingly threatening for China. The VWP's decisions to launch large offensives in early 1968 went against Chinese advice and raised the war to a new level of intensity and transparency. Likewise, the opening of negotiations with the United States went against Beijing's advice and was made without prior consultation with Beijing. Under such circumstances, continued deep involvement in Vietnam meant assuming substantially higher risks in a situation over which China had less control. Such a course would not have been prudent.