To the east of China lies Korea, and to the east of Korea lies Japan. Although there were countless cultural differences among the three countries, they were all heirs to the classical civilization of Tang and pre-Tang China, and they had much more in common with each other than any of them had with anyone else. The Koreans obtained firearms from the Chinese in the 1300s, but they kept firearms secret from the Japanese for almost two centuries, until the Japanese acquired muskets from the Portuguese in 1542. This discrepancy set up a revealing comparison between Chinese, Korean, and Japanese adaptation to European technology when the Chinese intervened to protect the Koreans against the Japanese in the 1590s. Despite their much longer experience with firearms, the Chinese and Koreans found themselves outgunned by the Japanese.

Korea

Korea is a peninsula roughly the same size as the island of Great Britain. It shares a border with Manchuria to the north, and it is a short distance by sea to China and Japan. Like Vietnam, Korea had once been a part of the Chinese empire, but it broke off from the Chinese empire during the extended period of disunity between the third and sixth centuries, and it successfully resisted reintegration by the Sui and Tang dynasties, even though Korea itself was not unified until 671.

The Chinese soon resigned themselves to the loss of Korea, and it remained independent under the rule of its own kings, who sent tribute to the Chinese on a regular basis.