after Han Dynasty, China went back to regional small kingdom for next 400 years.
In 581 CE Sui dynasty reunited, was short but influential. used Buddhism and the Confucian civil service system to establish legtimacy. Started construction of the Grand Canal, launched military campaigns to expand empire. Rebellions throughout 618 CE overthrew empire, but still had foundation for following dynasties.
Tang Dynasty was more focused on scholars than soldiers. expanded its territory beyond China proper to Tiber and Korea. also completed the Grand Canal. offered support to Buddhism, Daoism, and Confucisnism. Capital,Changan,was major political center foreign diplomats visited from the Byzantine and Arab worlds. Confucian beliefs solified into Chinese government via examination system.
Middle of 700s the Tang power declined because of high taxes causing tension in population. Led to regional rule and abdication of emperor. Afterwards period of rule by regional warlords for 50 years.