Hongwou had the satisfaction of restoring amicable relations with the King of Corea, a state in which the Chinese have always taken naturally enough a great interest from its proximity, as well as from an apprehension that the Japanese might make use of it as a vantage ground for the invasion of the continent. The King of Corea sent a formal embassy to Nankin, and when he died his son asked for and received investiture in his authority with the royal yellow robes at the hands of the Ming ruler. During this period it will be convenient here to note that the ruling power in Corea passed from the old royal family to the minister Li Chungwei, who was the ancestor of the present king. The last military episode of the reign of Hongwou was the conquest of Yunnan, which had been left over after the recovery of Szchuen, in consequence of the fresh outbreak of the Mongols in the north. This task was intrusted to Fuyuta, who at the head of an army of 100,000 men, divided into two corps, invaded Yunnan. The prince of that state offered the utmost resistance he could, but in the one great battle of the war his army fighting bravely was overthrown, and he was compelled to abandon his capital. The conquest of Yunnan completed the pacification of the empire, and the authority of Hongwou was unchallenged from the borders of Burmah to the Great Wall and the Corean frontier. The population of the empire thus restored did not much exceed sixty millions. The last ten years of the reign of Hongwou were passed in tranquillity, marred by only one unpleasant incident, the mutiny of a portion of his army under an ambitious general. The plot was discovered in good time, but it is said that the emperor did not consider the exigencies of the case to be met until he had executed twenty thousand of the mutineers.