When did China and North Korea start to take the Yalu River as the boundary? Where was the border before?

China and Korea have been bounded by the Yalu River since the Ming Dynasty, and there was no boundary before.

North Korea took advantage of the civil strife at the end of Yuan Dynasty to occupy the south of Yalu River. After the establishment of the Ming Dynasty, all the ministers of North Korea belonged to the Ming Dynasty, and there was no reason for the Ming Dynasty to go to war. Moreover, the core of the interests of the Ming Dynasty in Northeast China was Liaodong, and North Korea did not touch this bottom line. Even in the south of Yalu River, North Korea did not quickly establish effective rule, because there were Jurchen tribes there, which had been fighting and killing for hundreds of years.

At the beginning of the Ming Dynasty, after Zhu Yuanzhang took over the northeast political power from the Yuan Dynasty, he set up Liaodong viceroy (referred to as Liaodong viceroy) to govern the southern part of Northeast China. There are 25 guards in Liaodong Dusi, and Tieling Guards is one of them. People with a little knowledge of history may know that Tieling City in Liaoning Province today is the Tieling Health Center in the Ming Dynasty.

However, the "Tielingwei" discussed in this paper refers to the Tielingwei established on the east bank of the Yalu River (now Cijiang Road in North Korea, located in the east bank of the Yalu River in Ji 'an City, China 130) by order of Zhu Yuanzhang, the founding emperor of the Ming Dynasty.

From this little-known history, we can know that the land south of Tumen River and east of Yalu River has belonged to China since ancient times. Zhu Yuanzhang was deceived by North Korean diplomacy and was forced to move Tieling Wei to Liaodong because of the political need to attack the North Yuan, and gave up his territorial sovereignty over the eastern Yalu River. Its historical lessons are extremely profound.

Extended data:

The relationship between Ming Dynasty and Korea;

The Ming Dynasty maintained friendly diplomatic relations with the Korean dynasty for more than 200 years. 1392, Li Chenggui, the emperor of the Korean dynasty, ascended the throne, and Ming Taizu named him "Korea". The two countries established suzerain-vassal relations.

During the reign of Emperor Chengzu in Ming Dynasty, Emperor Chengzu officially awarded the title of korean king. The Korean dynasty adopted the policy of "doing great things" for the Ming Dynasty. 1592, Japan invaded Korea. Ming Shenzong sent troops to fight against the Japanese army and completely defeated the Japanese army on 1598. The Ming army sent troops twice and fought side by side with the Korean army and civilians, winning the war and writing a glorious page in the history of bilateral relations.

The Korean dynasty regarded this move of the Ming Dynasty as "the grace of reconstruction". At the end of the Ming Dynasty, with the rise of the Nuzhen nationality in Northeast China, the relationship between the two countries changed subtly. 1636, Huang taiji forced the Korean dynasty to sever the suzerain-vassal relationship with the Ming dynasty. However, since then, the Korean dynasty has still compared its heart with that of the Ming Dynasty, using the year number of Chongzhen, leaving out the Ming Dynasty for more than 300 years. For 300 years, the Ming Dynasty and North Korea basically maintained the relationship of hiring ambassadors.