The Mongols employed psychological warfare tactics during their conquests. If an enemy village did not submit, they could slaughter everyone in the first village they encountered. This would terrify other villages, causing them to surrender without resistance. Using this approach, they captured many lands without having to fight. They applied similar intimidation tactics to Đại Việt, sending envoys to deliver threats.
In 1266, sensing that the time was right to invade, the Mongol court began putting pressure on Đại Việt. Kublai Khan sent a letter demanding full submission, which included the Vietnamese king presenting himself at the Mongol court as a subordinate, offering royal family members as hostages, conducting a national census, paying taxes, and providing soldiers to serve the Mongols. However, Đại Việt refused to comply with these demands, agreeing only to pay tribute to maintain peace. These actions from the Mongols fueled strong resentment within Đại Việt. The king dismissed the demands, and the country began to prepare for war. That same year, a Vietnamese naval officer informed the king about the Mongols’ invasion plans.
In 1269, the Mongol court sent envoys again, this time bringing weapons into the palace—a sign of hostility in feudal times. When the Đại Việt king refused to kneel to receive Kublai Khan’s letter, the envoys complained, even demanding to be treated as equals to the king. Furious, the king ordered the leader of the envoys to be put under house arrest, guarded by soldiers with drawn swords. The envoy was treated harshly, being given hot, dirty river water to drink until he begged for clean water, which was only granted after much insistence.
Later, the Mongol court sent a letter of reproach, and the Đại Việt king responded defiantly, highlighting the previous exemption from certain tributes since 1263 and questioning the new demands. Kublai Khan sent a milder letter afterward, which led the king to send an emissary rather than directly replying.
During this time, the Mongols repeatedly demanded elephants as tribute. The king skillfully delayed, first claiming the elephants were too slow compared to Mongol horses, and later stating that the elephants were too attached to their homeland to be sent away. This diplomatic tension continued to grow.
In 1272, the Yuan dynasty sent Uriyang to Đại Việt under the guise of inquiring about the ancient Copper Pillar, a ruse to gather intelligence about the region for future invasions. The king dispatched Lý Kính Tu, accompanied by 2,000 soldiers, to lead Uriyang on a controlled tour, preventing him from gaining useful information.
By 1279, after conquering the Song Dynasty, Kublai Khan sent another envoy, Xītōng, to reprimand Đại Việt’s new king for not seeking an official appointment from the Mongol court. Xītōng arrived from the recently conquered Song territory, which unnerved the Vietnamese. The king responded diplomatically, asking Xītōng to follow the traditional route taken by previous envoys. Despite this, Xītōng continued to harass the court, demanding a grand reception and even striking a royal guard. When he refused to attend a banquet because it wasn’t held in a luxurious hall, the Đại Việt court responded by sending him on a long, arduous journey through mountains and jungles to wear him down.
When Xītōng finally presented Kublai Khan’s letter, it contained direct threats of war and demanded the Vietnamese king’s personal attendance at the Yuan court. The king, citing health and travel concerns, declined, which led Xītōng to return to China empty-handed.
In 1281, Kublai Khan escalated the situation by appointing Trần Di Ái, the king’s uncle, as a puppet ruler of Đại Việt. This “new government” was sent to Đại Việt, but was ambushed at the northern border. Xītōng was severely injured, losing an eye, and retreated to China. Trần Di Ái was captured and demoted to a common soldier. Although this internal defection initially weakened the Trần Dynasty’s position, the unity of the royal court under the leadership of key figures such as the Retired Emperor and the current king helped rally the country. This internal harmony was a crucial factor in Đại Việt’s eventual victory over the Mongols during their second invasion.
See also: Tran dynasty: the dynasty that defeated the Mongols 3 times
