China also exemplified the great changes that had occurred in the Communist world. For years our guiding principle was containment of what we considered a monolithic challenge. In the 1960's the forces of nationalism dissolved Communist unity into divergent centers of power and doctrine, and our foreign policy began to differentiate among the Communist capitals. But this process could not be truly effective so long as we were cut off from one-quarter of the globe's people. China in turn was emerging from its isolation and might be more receptive to overtures from foreign countries.