Đại Việt Defeats the Yuan’s Puppet Court
After the Yuan forces advanced into the interior of Đại Việt, a contingent of 5,000 soldiers escorting the puppet Đại Việt court also entered the territory. They believed that the Yuan had already defeated the Đại Việt troops at the passes they had crossed, assuming no further obstacles lay ahead. However, they were mistaken. In reality, Đại Việt’s forces remained vigilant along the borders of the Yuan’s advance. According to Prince Hưng Đạo’s strategy, local and regular troops stationed along the borders were instructed to engage and inflict casualties on the enemy before withdrawing. Thus, Đại Việt had far more than the 5,000 soldiers accompanying the puppet court, ready to disperse or launch an attack at any moment.
By the end of January 1288, the Yuan’s puppet court reached Lạng Sơn, which did not go unnoticed by Đại Việt. The regular and local forces coordinated an ambush at Nội Bàng Pass. The puppets and their escort troops were forced to retreat, burning local homes to slow down Đại Việt’s pursuit and buy time for the Yuan forces to come to their aid. They even attempted to leverage the terrain to their advantage against Đại Việt’s army. After a day of combat, Đại Việt emerged victorious, while the Yuan troops panicked and fled, resulting in heavy casualties. This swift victory highlighted the Yuan’s failure to control the territories they had occupied. Following the battle, Đại Việt dispersed its forces and withdrew safely.
Despite Toghan’s orders to establish a strong base at Vạn Kiếp to facilitate logistics and military support, the situation had not improved significantly since previous conflicts.
The Yuan Gets Lost in Đại Việt’s Territory
Thanks to thorough preparations and a variety of ships, Đại Việt’s headquarters remained highly mobile. After retreating from Thăng Long, the court and the majority of the main forces moved directly to Thiên Trường, pursued by the Yuan cavalry and navy. Confident in his naval superiority, Omar sent a letter threatening the Đại Việt king: “If you flee to the sky, I will pursue you. If you run on the ground, I will chase you. If you escape to the mountains, I will follow. If you dive underwater, I will catch you.” However, they would not be able to maintain their bravado for long.
Đại Việt deployed multiple troops to counter the Yuan’s pursuit along the Red River. Believing the king was at Cảm Nam, Toghan personally led an assault while ordering Abaci to attack Hàm Tử. After overcoming two fortresses, they faced further resistance at Hải Thị. However, it was too late for them to catch up with the main force and its leaders. Toghan, Omar, and Abaci scoured Thiên Trường and Long Hưng in search of the Đại Việt king, but to no avail. In a fit of anger, Omar ordered his troops to vandalize the tomb of the former king, Trần Thái Tông. Unable to locate the deceased king’s remains, they devastated the site and left a trail of destruction in their wake.
Upon learning that Đại Việt’s king was at Giao Thuỷ port in Thiên Trường, Toghan immediately led his forces there, but they again lost track of him. They were forced to return to Thăng Long to expand their territorial control, sending soldiers out to forage for food. Omar directed his forces to An Bang port to retrieve logistics vessels under Zhāng Wénhǔ’s command, unaware that these vessels had been destroyed or captured by Prince Nhân Huệ the previous month.
Despite the Yuan’s formidable navy, Đại Việt’s naval strength proved to be even greater. When Toghan arrived at Giao Thuỷ port, Đại Việt’s navy had already set sail, dispersing into various formations. Prince Hưng Đạo led a portion of his forces north, remaining active in coastal waters, which misled the Yuan into believing that Đại Việt was concentrated in that area. In reality, this was a ruse to deceive Yuan spies. Consequently, the Yuan forces, believing they had gained the upper hand, engaged in several victories (as Đại Việt troops were divided into smaller groups to mislead the Yuan). Meanwhile, the king and the retired king managed to discreetly lead the remaining forces to Thanh Hóa without Yuan detection. Later, when a Yuan contingent under Siktur confronted Prince Hưng Đạo near Tháp Sơn, they were quickly defeated. The Yuan infantry then retreated to Thăng Long and Vạn Kiếp, pillaging along the way as they awaited Omar’s return with supplies.
As for Omar, he was tasked with retrieving the logistics vessels commanded by Zhāng Wénhǔ. Đại Việt positioned their navy to ambush this force with 1,000 war vessels of various sizes. Their objective was to deplete the Yuan navy and then withdraw. Upon engagement, Omar’s forces fought back, but Đại Việt launched continuous assaults from multiple directions, resulting in significant Yuan casualties and the loss of 300 war vessels. Despite the Yuan’s numerical advantage, Đại Việt ultimately withdrew as their navy remained numerous. After passing Đại Bàng port, Omar’s forces encountered Prince Hưng Đạo’s troops waiting for them in the Tháp Sơn water region. With great effort, Omar managed to lead his army past the ambush and proceeded directly to An Bang harbor, expecting the logistics vessels to still be there. Rather than continue attacking the Yuan navy, Prince Hưng Đạo concentrated his forces on assaulting Toghan’s land army, gaining further territorial control and directly harassing the Yuan base at Vạn Kiếp from the east.
See also: Tran dynasty: the dynasty that defeated the Mongols 3 times
