Reasons why the Song Dynasty's great poet So Dong-pa opposed trade with Goryeo

 During the reign of King Munjong of Goryeo, diplomacy and trade with Song were active. In the 34 years from 1047 to 1081, during the reign of King Munjong, Song's official trade ship entered Goryeo 39 times. Goryeo imported more than 100 kinds of goods from Song, including books, clothing, medicinal materials, and musical instruments. Song also imported paper, brushes, lacquerware, pottery, and silk from Goryeo. It is said that a large-scale trading company went back and forth, with the number of merchants reaching 200 once the trading ship entered. In addition, trade was so constant that guesthouses for envoys and merchants were installed in both countries. However, opposition to this active exchange occurred during Song's mediation. Song's representative poet and well-known to us (the pen name is Dongpa-ro, then Byeongbu Sangseo) was a representative anti-communist. The biggest reason he opposed trade with Goryeo was, "We have no profit at all, but Goryeo is taking great profits." In addition, the Sodong faction was lactatively opposed to trade with Goryeo for the following reasons. First, it causes inconvenience to entertain envoys and merchants, and second, it is too expensive to send and receive goods. Third, the goods sent from Song are introduced into the enemy country of Kitan through the hands of the Goryeo people. Fourth, wherever Goryeo envoys and merchants go, Song's mountain stream map is prepared, so state secrets are leaked. Fifth - Koryo is an ally of Kitan. However, these objections were not encouraged. This is because Song, who is confronting Kitan, could not ignore Goryeo, a powerhouse in the northeast. Through equidistant diplomacy with Song and Geoga, Goryeo was able to occupy an advantageous position not only in defense but also in trade.