The Great Battle Between Đại Việt and the Yuan Navy
The Yuan dynasty made every effort to overcome the challenges they faced in previous conflicts, particularly regarding their naval capabilities and logistics. However, after initially reaching the peak of their military strength, they quickly encountered the same problems they had before. Their ships were large but lacked maneuverability, a necessity for transporting troops to Đại Việt via sea routes. In contrast, Đại Việt possessed a diverse array of ships suited for various purposes. This flexibility partly explained why, despite their occupation of the capital Thăng Long, they failed to capture the King of Đại Việt. The leaders of Đại Việt allowed the Yuan to temporarily control the land to minimize unnecessary bloodshed. Their strategy was to weaken the Yuan over time before launching counterattacks, using the geography of the land to their advantage.
While awaiting Omar’s arrival with the logistics vessels, the Yuan resorted to pillaging for food due to a severe shortage. However, they struggled to acquire sufficient supplies because of resistance from the local population. Abaci advised Toghan, stating, “The enemy retreats to wear us down before launching a counterattack. Most of our soldiers are from the North, and as the season shifts from spring to summer, there’s a risk of epidemics. If that occurs, we won’t be able to maintain control for long. We should stop pillaging and instead divide our troops to lure local civilians and capture King Nhật Huyền of Đại Việt.” While this suggestion was strategic, its implementation was complicated by their food shortage, which made halting plundering unfeasible. Additionally, spreading their forces would expose them to ambushes from Đại Việt.
Bad News for the Yuan About Their Logistics Vessels
As battles raged across the region, news of the destruction of Zhāng Wénhǔ’s logistics vessels reached the Đại Việt court only later. It wasn’t until early February 1288 that the Retired King received the news, which delighted him. He announced to the court, “The logistics the Yuan have been waiting for have now been destroyed. They are likely still arrogant, unaware of this setback!” He then released several Yuan prisoners, allowing them to return and inform their leaders of this development.
The news sent shockwaves through the Yuan ranks. Toghan retreated to the base he had ordered constructed at Vạn Kiếp, burning many buildings and structures in Thăng Long before departing. In addition to the vessels under Zhāng Wénhǔ’s command, the Yuan court had dispatched two other groups to deliver supplies for their army in Đại Việt. Instead of launching an offensive, Toghan and his forces chose to wait for their supplies. Unfortunately, one of the shipments encountered a storm and drifted to Hainan, while another fell victim to a storm and ended up in Champa. While the Đại Việt forces thrived at sea, the Yuan struggled with luck whenever they traveled by sea routes. Coupled with previous heavy losses during their naval campaigns in Champa, Japan, and elsewhere, this highlighted their limited understanding of maritime navigation and weather patterns, contributing to their failures in coastal regions like Đại Việt, Champa, Japan, and Java.
After nearly a month of waiting, Omar and his navy returned to Vạn Kiếp to join Toghan’s forces. Despite their attempts to scavenge for food along the way, it proved insufficient for their large army. After about three months in Đại Việt, the Yuan began to face starvation once again.
An Uneasy Withdrawal
The regular forces of Đại Việt, along with various scattered troops, consistently attacked Yuan barracks, seizing control of numerous strongholds. In response, Toghan moved his army from Thăng Long to Vạn Kiếp but faced relentless attacks. In the battle at Tam Giang, the Yuan commander Đường Tông was killed. Đại Việt gradually regained control over significant areas, including the capital, Thiên Trường, and Long Hưng.
As food supplies dwindled, Abaci led his troops to plunder. The situation continued to deteriorate, and with the arrival of summer, epidemics began to spread among the Yuan soldiers. Meanwhile, Prince Hưng Đạo managed to secure most of the sea routes. Realizing the urgency of the situation, the King advanced his forces from Thanh Hóa to Tháp Sơn to join him. Aware of this movement, Toghan ordered Abaci to strike in an attempt to regain control. However, Đại Việt capitalized on the terrain to mount a successful defense. Unable to secure a victory, Abaci was forced to retreat.
To buy more time and further weaken the Yuan, Đại Việt employed various tactics to conceal their own movements. Prince Hưng Ninh volunteered to act as an ambassador to the Yuan barracks. When he arrived at Toghan’s camp, the commander proposed that he serve the Yuan instead, promising him the future kingship of Đại Việt. If he had accepted, it would have been a significant loss for Đại Việt, given his knowledge of their military. The prince pretended to need more time to consider Toghan’s offer, which led Toghan to believe he would eventually agree. This assumption caused Toghan to delay his campaigns. Meanwhile, Đại Việt forces launched nightly assaults on the Yuan barracks. During the day, they closed the gates of their ramparts to avoid large-scale battles and instead engaged in guerrilla warfare.
When it came time for the ambassador to respond, he feigned acceptance of Toghan’s offer, revealing critical locations in Thăng Long to facilitate the Yuan’s attack. However, when the Yuan entered the capital, they found it deserted. Infuriated, Toghan learned he had fallen into Đại Việt’s trap and ordered his men to burn the structures in the capital. The ambassador, meanwhile, managed to escape back to the Đại Việt camp.
As the food shortage worsened and the heat intensified, Toghan was forced to order a withdrawal. However, this proved to be a difficult task, as Đại Việt had set traps and ambushes everywhere. The commanders of the Yuan navy grew weary of the hidden threats in the sea routes and from the Đại Việt navy. They suggested destroying all the vessels and proceeding overland instead. Initially, Toghan considered the idea, but other officials dissuaded him, arguing that destroying ships would be a disgrace for an empire like the Yuan. Moreover, withdrawing via two different routes would draw the Đại Việt army into attacking the navy, allowing the infantry and cavalry to retreat more safely. Ultimately, Toghan opted for a two-pronged withdrawal.
Omar Captured and His Naval Forces Decimated
Đại Việt was determined not to allow their enemy to withdraw without consequence. Their goal was to demoralize the Yuan soldiers, ensuring they would abandon any thoughts of future invasions. The leaders of Đại Việt aimed to lure all the Yuan vessels into a wide river and destroy them, showcasing their own naval strength to the Yuan, signaling that even if the Yuan attempted to build a formidable navy, Đại Việt would remain superior.
Prince Hưng Đạo instructed his troops to drive iron poles into the waters of the three northern branches of the Bạch Đằng River to block enemy ships during low tide. They also set up ambushes and traps, with the help of an elderly woman who sold goods by the riverbank, who provided insights into tidal patterns. Under the guidance of a general, local civilians worked swiftly to erect the stakes, but it was no easy task. The stakes could only be planted when the water level was low, as the rushing waters made it challenging to do so at other times.
Even after the stakes were installed, timing was crucial. If the enemy entered the river while the water level was high, they could easily pass without obstruction, rendering the stakes ineffective. Thus, they needed the Yuan to enter the river at precisely the right moment and retreat upstream as the tide began to ebb. At that point, the strong current would push the Yuan vessels toward the stakes, trapping them. To avoid detection, Đại Việt needed to ensure that the Yuan’s ships did not see the stakes beneath the water. They aimed for the tide to be high, but not too high, to maintain the element of surprise and to gather the Yuan vessels in one location for a devastating “fire ship” attack (using burning vessels made of straw and flammable materials).
To execute this plan, Đại Việt’s small flotilla constantly provoked and harassed the Yuan formation, slowing their advance. This strategy allowed Đại Việt ample time to prepare and plant the stakes while tiring the Yuan soldiers before the main confrontation. Đại Việt also stationed their primary forces at critical river points, forcing the Yuan vessels to choose alternative routes. Any attempt to bypass the traps would leave them vulnerable to becoming trapped in a food-deprived situation. Ultimately, the Yuan followed the path that Đại Việt had intentionally set for them.
On April 9, 1288, the Yuan navy approached the Đá Bạch River, where Đại Việt’s navy launched an attack while waiting for the perfect moment. After a while, they pretended to retreat. Omar, believing that the Đại Việt navy was in full withdrawal, ordered his troops to pursue them. As they rushed into the Bạch Đằng River, the tide began to ebb rapidly. It was only then that the Yuan realized they had walked into a trap, as their vessels became entangled in the iron poles. With the strong currents pushing them downstream, they were unable to turn back or stop. Soon, Đại Việt’s fire ships, filled with flammable materials, were released, crashing into the Yuan vessels and igniting the river in flames.
At this critical moment, the best of Đại Việt’s navy and the ambushed troops launched a fierce attack, raining arrows upon the Yuan soldiers. Those who had pretended to withdraw now returned with renewed vigor.
The Yuan commanders struggled to reorganize their forces to counter Đại Việt’s relentless assault. Phàn Tiếp attempted to disembark his troops to leverage the land’s geography, but Đại Việt had set ambushes in anticipation of this move. As a result, this Yuan unit suffered heavy losses and was driven from the river. Meanwhile, at other locations, the rapidly receding tide revealed the stakes, causing even more Yuan vessels to become ensnared and sink. Those ships that remained afloat were too afraid to move, fearing the hidden poles.
Amidst all this chaos, Đại Việt’s forces took advantage of their clustered positioning to launch a barrage of arrows against the Yuan vessels. Despite the overwhelming circumstances, the Yuan soldiers had no choice but to fight back. However, Prince Hưng Đạo was not simply looking to defeat the Yuan navy; he aimed to destroy it entirely. While conventional military strategy often advocates for allowing part of the enemy to escape for future pursuit, this time he had compelling reasons to take a different approach.
At the height of the battle, the King of Đại Việt, along with the Retired King and Prince Hưng Đạo, led their finest troops into the fray. The sight of them invigorated the Đại Việt soldiers while inciting panic among the Yuan troops.
Ultimately, the Yuan navy was completely annihilated. The soldiers were either captured or killed, and approximately 600 of their vessels were either seized by Đại Việt or sunk. Omar, along with Tích Lệ Cơ Ngọc, was taken captive.
See also: Tran dynasty: the dynasty that defeated the Mongols 3 times
