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 were the key factors that helped the centripetal forces to get back to the imperial norm? It begins with the final stage of decline of the Tang dynasty (618-907) and ends 50 years later when it became clear that the foundations for a last push towards unification were in place.