The oneness of China is the norm. Periods of divisions are aberrations. This is how Chinese thinkers, leaders and ultimately the majority of Chinese people have regarded Chinese politics and history for more than 2,000 years. The oneness was never perfect. As long as certain minimal conditions were met and the polity which proclaimed that oneness was widely acknowledged, that was enough. Chinese ruling elites adopted this pragmatic approach so they could ensure that the ideal could always approximate China's reality. This is a revised edition of a study undertaken to explain what happened during one of the worst periods of division in Chinese history. What