SOUTH BEND, Indiana — Second honeymoons rarely, if ever, recapture the zest of lost love. Yet ever since the Soviet Union's collapse in 1991, Russia and China have sought to rekindle the close relations that once supposedly existed between the Soviet Union and Mao's China before Nikita Khrushchev's denunciation of Josef Stalin in 1956. But that renewed Sino-Russian marriage always smacked more of convenience — aimed as it was at checking American hegemony — than of true romance. Now Russia's invasion of Georgia has shattered even the illusion of attraction.

In 1969, the Chinese and Soviet armies exchanged fire across their disputed border. Recently, the two countries signed an agreement that seemed to put an end to their long border dispute. The agreement was a sort of followup to the visit to Beijing of Dmitry Medvedev, who made China one of his first official trips abroad after being elected Russia's president.

During Vladimir Putin's presidency, Chinese and Russian troops engaged in joint military maneuvers, and the two countries became dominant powers in the Shanghai Cooperation Organization (SCO), which, to some Western observers, looked like an effort to counterbalance NATO. There were also years of "Russia in China" and "China in Russia" cultural exchanges, meant to underscore that the two countries were tied together not just by geopolitical pragmatism, but by genuine cultural/historical ties as well.