The primary transportation routes of the Yuan Dynasty, known as the postal routes, were developed to facilitate the movement of troops and military supplies. Later, these routes became important for official business and trade between Yuan and neighboring countries. Although land transportation routes connecting the central plains of China with Annam began to be established during the Tang Dynasty, they were not actively used until the Yuan Dynasty. The transportation routes between Yuan and Annam were straightened to shorten the travel time by eliminating detours and to enhance the stability and continuity of the routes by constructing postal stations every 60 li. The primary land transportation routes between the two countries were (1) Chongqing-Mengzi-Thang Long and (2) Chongqing-Yongzhou-Thang Long. The first route, departing from Chongqing in Yunnan Province, went directly through steep mountains to reach Mengzi, and then followed the Hong River into Annam. This was the route used by envoys from both countries before the Southern Song conquest; however, it was time-consuming due to the mountainous terrain. The second route was developed after Yuan took control of Yongzhou, becoming the fastest transportation route between the two countries and mainly used for envoys and trade. This route was established by Toghon, featuring a dense network of postal stations every 60 li within Annam, which intimidated the king of Annam. Since the establishment of these postal stations in 1284, Annamese envoys traveled along this route to Dadu every one to two years to deliver tributes, as well as to transport goods for the Yuan court. Annam’s tributes were used to supply luxuries for the imperial family, while gifts from Yuan were used as ceremonial items to enhance the authority of the king of Annam. During this period, Yongping, a postal station at the entrance to Annam, flourished as a hub for private trade.