Work in the military research units devoted to nuclear weapons and missiles presumably continued, although the secrecy surrounding strategic weapons research made it difficult to assess the impact of the Cultural Revolution in that sector. In the most general sense, the Cultural Revolution represented the triumph of anti-intellectualism and the consistent, decade-long deprecation of scholarship, formal education, and all the qualities associated with professionalism in science. Intellectuals were assumed to be inherently counter-revolutionary, and it was asserted that their characteristic attitudes and practices were necessarily opposed to the interests of the masses. Universities were closed from the summer of 1966 through 1970, when they reopened for undergraduate training with very reduced enrollments and a heavy emphasis on political training and manual labor. Students were selected for political rectitude rather than academic talent. Primary and secondary schools were closed in 1966 and 1967, and when reopened were repeatedly disrupted by political struggle. All scientific journals ceased publication in 1966, and subscriptions to foreign journals lapsed or were canceled. For most of a decade China trained no new scientists or engineers and was cut off from foreign scientific developments. During the decade between 1966 and 1976, China's leaders attempted to create a new structure for science and technology characterized by mass participation, concentration on immediate practical problems in agriculture and industry, and eradication of distinctions between scientists and workers. Ideologues saw research as an inherently political activity and interpreted all aspects of scientific work, from choice of topic to methods of investigation, as evidence of an underlying political line. According to this view, research served the interests of one social class or another and required the guidance of the party to ensure that it served the interest of the masses. The early 1970s were characterized by mass experimentation, in which large numbers of peasants were mobilized to collect data and encouraged to view themselves as doing scientific research. Typical projects included collecting information on new crop varieties, studying the effectiveness of locally produced insecticides, and making extensive geological surveys aimed at finding useful minerals or fossil fuels. Mao Zedong took a personal interest in earthquake prediction, which became a showcase of Cultural Revolution-style science. Geologists went to the countryside to collect folk wisdom on precursors of earthquakes, and networks of thousands of observers were established to monitor such signs as the level of water in wells or the unusual behavior of domestic animals. The emphasis in this activity, as in acupuncture anesthesia, was on immediate practical benefits, and little effort was made to integrate the phenomena observed into larger theoretical frameworks. The effects of the extreme emphasis on short-term problems and the deprecation of theory were noted by Western scientists who visited China in the mid and late 1970s.