Since establishment of Joseon, the Jurchen had provided local products like furs and thick minks called sables to Joseon. They gave their local products in exchange for iron works and other gifts from the Joseon, making these exchanges at yeok (驛) or village stations and or at gwan (館) or official trading posts in the capital.
Joseonbegan prohibiting the trade of iron goods with Jurchen. The representative, unique product was sable(貂皮) among fur, which could be exchanged with iron goods of Joseon. From then times, sable was popular in Ming dynasty so that sable trading between Ming dynasty and Jurchen was prevalent. Sable was popular in Joseon too. In the middle period of Joseon, some ordinary people wore these sables. The Joseon government asked Pyeongan-do province and Hamgyeong-do to provide sables as tributes. However, the quality and production capacity was not on par with the Jurchen’s. So quality sable was mostly imported from Jurchen in Manchuria. Popularity of sable was connected to prevalent private trading.
Joseon people exchanged iron goods, ox, and horse with sable for tribute- merchants for profit. This broke the law. As long as Joseon did not abolish the giving of sables as tributes, private trading in sables could not be controlled. Rather merchants gathered to Bukdo (北道) like the clouds. In the period of Yeonsan-gun and Joongjong, sable trading was more prevalent.
This was partially because of local governors who should regulate such trading. Chief officers and boundary commanders conspired with ministers in central government and even led sable trading with Jurchen. Chief officers in the northern area were actively involved in sable trading. For example, they opened Gwansi (關市) indiscriminately.
As iron goods of Joseon were sent to Jurchen through sable trading, some worried that Jurchen could make iron arrow and iron armor. Flow of iron products into Jurchen drove development of military weapon in the Jurchen.
And flow of iron goods, ox, and horse to Jurchen unfavorable influenced the economic and military situation. For example, people should plow field or rice field by manpower only instead of using ox or horse. As a result, some say that the Jurchen grew stronger, while Joseon became impoverished. Furthermore, the use of horses in the army declined in the Hamgyeong-do. The number of soldiers also decreased accordingly. People there wandered around the country because they could not satisfy the burden tribute of sable.
Fence in Tumen River basin was called Fence(藩籬)․ Boundary Jurchens(藩胡) and so on and were subjects under the Joseon politically and economically. However, the economic situation reversed with sable trading. Jurchen people were seen as greater than the Joseon people. Some Joseon people crossed the border into Jurchen. Boundary commanders overexploited sables from Jurchen or restricted purchasing. This led to Jurchen unrest. At last, this caused the Jurchen to invade Joseon. With the rebellion of Fence, Jurchen separated from Joseon.