In the 570s and 580s the long period of division in China was brought to an end under the leadership of the Sui (sway) Dynasty. Yang Jian, who both founded the Sui Dynasty and oversaw the reunification of China, was from a Chinese family that had intermarried with the non-Chinese elite of the north. His conquest of the south involved naval as well as land battles, with thousands of ships on both sides contending for control of the Yangzi River. The Sui reasserted Chinese control over northern Vietnam and campaigned into Korea and against the new force on the steppe, the Turks. The Sui strengthened central control of the government by curtailing the power of local officials to appoint their own subordinates and by instituting in 605 C.E. competitive written examinations for the selection of officials. Preparing for such exams would come to dominate the lives of educated men in later centuries.

The crowning achievement of the Sui Dynasty was the construction of the Grand Canal, which connected the Yellow and Yangzi River regions. The canal facilitated the shipping of tax grain (that is, grain paid as tax) from the prosperous Yangzi Valley to the centers of political and military power in north China. Henceforth the rice-growing Yangzi Valley and south China played an ever more influential role in the country’s economic and political life, strengthening China’s internal cohesion and facilitating maritime trade with Southeast Asia, India, and areas farther west.

Despite these accomplishments, the Sui Dynasty lasted for only two reigns. The ambitious projects of the two Sui emperors led to exhaustion and unrest, and in the ensuing warfare Li Yuan, a Chinese from the same northwest aristocratic circles as the founder of the Sui, seized the throne.