The countries of East Asia — China, Japan, and Korea — all underwent major changes in the six centuries from 800 to 1400. In China the loosening of the central government’s control of the economy stimulated trade and economic growth. Between 800 and 1100 China’s population doubled to 100 million, reflecting in part the spread of wet-field rice cultivation, especially in the south. The economic center of China shifted from the north China plain to the south, the milder region drained by the Yangzi River.

In the Song period, the booming economy and the invention of printing allowed for expansion of the scholar-official class, which came to dominate government and society. Repeatedly, the Song government chose to pay tribute to its militarily powerful neighbors — first the Khitans, then the Jurchens, then the Mongols — to keep the peace. Eventually, however, Song fell to the Mongols.

During the Koryŏ Dynasty, Korea evolved more independently of China than it had previously, in part because it had to placate powerful non-Chinese neighbors. The commercial economy declined, and an increasing portion of the population was unfree, working as slaves for aristocrats or the government. Military strongmen dominated the government, but their armies were no match for the much larger empires to their north. The period of Mongol domination was particularly difficult.

In Heian Japan, a tiny aristocracy dominated government and society. A series of regents, most of them from the Fujiwara family and fathers-in-law of the emperors, controlled political life. The aristocratic court society put great emphasis on taste and refinement. The Heian aristocrats had little interest in life in the provinces, which gradually came under the control of military clans.

After a civil war between the two leading military clans, a military government, called the shogunate, was established. The Kamakura Shogunate was dominated by a military class of samurais. Two invasions by the Mongols caused major crises in military control. Although both times the invaders were repelled, defense costs were high. During this period culture was less centered around the capital, and Buddhism spread to ordinary people.