At Vạn Kiếp, Prince Hưng Đạo commanded an army of 200,000 soldiers, while Toghan led a much larger force of 500,000. The Yuan sought to defeat the Trần’s main army before advancing on the capital of Đại Việt, so they targeted Vạn Kiếp first. They deployed both cavalry and infantry as their primary forces and constructed warships using stolen timber and materials. Additionally, they acquired ships from previous battles and seized civilian vessels, ultimately amassing several hundred ships. Under the command of Omar, the best naval commander of the Yuan dynasty, this naval force was tasked with coordinating with the ground troops and attacking Đại Việt forces during their retreats.
In mid-February 1285, Toghan appointed Omar to lead a vanguard of 300,000 soldiers against the Đại Việt troops, while he followed with the rest of his army. Overconfident in their superior cavalry and renowned archery skills, the Yuan forces underestimated the resolve of the Đại Việt soldiers. The Vietnamese navy successfully thwarted the Yuan’s advances time and again, inflicting heavy losses. Despite this, the Yuan continued their assault, as their numbers overwhelmed the resistance. Other Yuan generals coordinated their attacks with Omar’s forces, launching offensives from multiple directions. While the Đại Việt Navy excelled on the rivers, the ground situation began to shift unfavorably.
Receiving urgent reports of the Yuan advance, the Emperor of Đại Việt dispatched 1,000 vessels and 100,000 soldiers from Thăng Long to Vạn Kiếp to support Prince Hưng Đạo. However, the Đại Việt forces remained outnumbered. After three days of intense fighting, the situation grew dire for Đại Việt, prompting the King and Prince Hưng Đạo to order a strategic withdrawal. As noted in Prince Hưng Đạo’s writings on military strategy, “The wise do not seek numerous victories, but rather ensure the ultimate, decisive triumph.”
Omar and his navy struggled to prevent the withdrawal of the Vietnamese troops, who maintained control of the main river routes. Both sides endured significant losses throughout the prolonged battle.
The Capital
Following their victory at Vạn Kiếp, the Yuan forces advanced through Bắc Giang, quickly taking control of areas with minimal Đại Việt resistance. Their march was marked by atrocities, especially against Vietnamese soldiers bearing the tattoo that read “Kill the Yuan-Mongols!”
In preparation for the impending attack, the Đại Việt government had preemptively evacuated resources and civilians. Troops were stationed near the capital to guard the rivers, erect defensive barriers, and stockpile weapons. Although the Yuan vanguard was only a short distance across the river from the Đại Việt forces, they hesitated to launch an immediate attack, seemingly aware of Đại Việt’s defensive readiness.
After the Battle of Vạn Kiếp, the Yuan troops gathered near the Red River, just across from the capital. While the Đại Việt were adept at naval warfare, the Yuan struggled in these waters, and the numerous rivers in Đại Việt posed a challenge for their advance. Instead of attacking, the Yuan awaited reinforcements and attempted to establish their own naval presence.
As tensions mounted, the King of Đại Việt sought a negotiator to approach the Yuan barracks, under the pretense of diplomacy—an actual ploy to gather intelligence on Yuan forces. The prospect was perilous, and few volunteered, but finally, Đỗ Khắc Chung stepped forward, saying:
- “Your Majesty, I may not be the most capable, but allow me to try!”
Pleased by this display of bravery, the King remarked:
- “It is impressive to see a noble horse among the cart horses!”
Đỗ Khắc Chung was sent to the Yuan camp with the King’s letter. Upon arrival, Omar confronted him:
- “Your King is uncouth, ordering our soldiers to tattoo ‘Kill the Mongols’—a grave insult to our troops!”
Đỗ Khắc Chung replied:
- “Just as dogs bark at strangers, they mark themselves to show loyalty. Our Emperor was unaware. As his close Mandarin, why would I bear such a tattoo?”
To support his claim, Đỗ Khắc Chung displayed his own arm to Omar. The commander then questioned:
- “Why hasn’t your country come to negotiate, instead choosing to fight? What fate awaits a mantis attempting to stop a wheel?”
Đỗ Khắc Chung retorted:
- “Your Great Commander did not adhere to the ancient customs when trying to conquer the Kingdom of Yan. He should have stationed at the border and sent a letter before advancing. By attacking us, you’ve committed a grave offense. Even a worm will turn when provoked!”
Omar warned:
- “Our forces are merely passing through to conquer Champa. If your King does not come to discuss terms, we will devastate your country without mercy!”
Upon returning to Đại Việt, Đỗ Khắc Chung reported valuable intelligence about the Yuan troops to the King. Soon after, the Yuan forces launched an attack, which ultimately failed, prompting Toghan to commit all his forces to a concerted assault. They focused their efforts on the southern part of the capital, aiming to prevent any further withdrawals by Đại Việt.
Despite the heavy losses incurred by Toghan’s forces, they continued to advance toward the fortress. Unbeknownst to Toghan, most of Đại Việt’s main troops had successfully withdrawn. The Yuan forces, having occupied the fortress after a costly battle, proceeded to the capital, only to discover it deserted. The valuable items and people had already been evacuated, leaving behind only remnants of Kublai Khan’s orders, which illustrated that the Yuan’s threats held no weight in Đại Việt. Among the documents were directives urging civilian resistance against the Yuan. Realizing the gravity of the situation, Toghan ordered his troops to pursue Đại Việt, despite their earlier celebration of victory, as the looming fear of famine like that from the previous Đại Việt-Mongol war began to set in.
Yuan Troops from Yunnan
Simultaneously, Prince Chiêu Văn mobilized his forces to confront the Yuan troops advancing from Yunnan. While the exact number of soldiers in this contingent is unknown, it is believed that under the command of Naxirut Din, a high-ranking official of the Yuan, their ranks were at least 10,000 strong. This Yuan troop was primarily tasked with dispersing the Đại Việt forces before joining Toghan’s army. To prevent a coordinated assault from both Yuan factions, the Đại Việt were compelled to spread their own forces thin.
The Đại Việt main army was concentrated in the Central Mainland, leaving Prince Chiêu Văn with a relatively small contingent. His forces included a diverse mix of Vietnamese, ethnic minorities, and soldiers from the Song dynasty seeking a place to belong and avenge their homeland. However, the varied backgrounds of these troops posed a challenge for cooperation due to differences in language and customs.
The Đại Việt government did not have designated officials for minority groups; these regions operated autonomously, maintaining their own military forces. They showed loyalty by paying taxes and tributes, and cooperating during times of war, although this cooperation often meant that the Đại Việt government had limited intervention in their internal matters. In many ways, the government resembled a coalition of distinct communities.
In the Quy Hóa region, local leaders Hà Đặc and Hà Chương led the resistance against the Yuan invasion. Utilizing guerrilla warfare tactics, Hà Đặc’s forces successfully ambushed the enemy. Meanwhile, Prince Chiêu Văn engaged Naxirut Din’s troops, inflicting losses while strategically retreating.
Upon reaching the region, Naxirut Din turned toward Thu Vật, intent on decisively defeating Prince Chiêu Văn. However, the Prince’s mission focused on diminishing the Yuan’s strength while preserving his own forces. After several skirmishes that weakened the enemy, Prince Chiêu Văn ordered a strategic withdrawal, aiming to exploit the terrain for further ambushes.
Naxirut Din faced significant difficulties due to the ambushes from the minority troops. He was forced to disperse his own soldiers to counter these attacks, ultimately reducing his available forces to just 1,000 men to support Toghan’s army. Although the Đại Việt forces did not achieve a clear victory, they successfully disrupted the Yuan’s plans for a multi-directional assault. Nevertheless, challenges remained, as Toghan prepared to strike from the north while Sogetu advanced from the south. Toghan positioned his navy at the forefront, with cavalry backing them up.
The Pursuit of the Yuan Troops
The Đại Việt faced severe losses. In a heart-wrenching sacrifice, Princess An Tư offered herself to Toghan in an effort to slow the advance of the Yuan forces. This decision was a deep sorrow for the dynasty, as those escorting her wore funeral attire. Her sacrifice bought the Đại Việt army precious time to regroup.
To further safeguard the main force’s retreat, Đại Việt strategically deployed additional troops to counter the Yuan’s pursuit. At Đà Mạc, Trần Bình Trọng commanded a small force of several thousand soldiers and a few vessels to hold off the advancing Yuan troops. The battle took place along a river, where Đại Việt leveraged the geography to their advantage against a larger enemy force. Despite repeated attempts, the Yuan failed to penetrate their defenses, suffering heavy losses over the course of three to four days. Frustrated and outmatched, Trần Bình Trọng was eventually captured, and most of his men were killed in the process, as the Yuan Navy and cavalry coordinated their assault.
Recognizing Trần Bình Trọng’s skill and courage, the Yuan leaders attempted to persuade him to join their ranks. However, he resolutely rejected their offers, even refusing their food. When asked if he would like to become a prince in the Yuan dynasty, he defiantly replied:
- “I would rather be a ghost in the South than a prince in the North!”
Realizing they could not sway this formidable general, the Yuan executed him at the age of 26.
The news of Trần Bình Trọng’s death deeply mourned every member of the Đại Việt court and the Trần royal family. In his honor, the King posthumously bestowed the title Prince Bảo Nghĩa, later elevating him to Great Prince Bảo Nghĩa. His bravery in battle discouraged the Yuan troops, making it increasingly difficult for them to pursue the King of Đại Việt. Even though Đại Việt suffered a tactical defeat, strategically, they emerged victorious.
Initially, Prince Hưng Đạo planned to send two additional forces to confront the Mongols, allowing the main army enough time to withdraw and regroup. One of the strategically chosen locations was Hải Thị, where Đại Việt could exploit the geography to their advantage. Thanks to Trần Bình Trọng and his troops, the subsequent battle at Hải Thị shifted its focus from defense to offense. Đại Việt fortified the riverbanks with obstacles to restrict the Yuan Navy’s access and deployed infantry to support naval forces.
Building on the lessons learned from the battle at Đà Mạc, the Yuan forces improved their organization, launching a coordinated assault with infantry, cavalry, and navy. The fighting was intense, but Đại Việt managed to inflict significant casualties before retreating to Thiên Trường. The Yuan forces rapidly passed through Hải Thị, but some troops were dispatched to pursue the Đại Việt, only to find that they had reorganized and outnumbered their adversaries. Furthermore, the Yuan soldiers were fatigued, which compelled Li Heng to lead his troops back to Toghan’s position instead of continuing the chase.
From the onset of their invasion, the Yuan had won nearly every major battle. Yet, they remained oblivious to the fact that they had fallen into a strategic trap set by Đại Việt. As the Yuan gained territory, they were forced to stretch their forces thin to address the diverse and dispersed military threats posed by Đại Việt’s guerrilla tactics. The Yuan needed a significant number of soldiers to confront Đại Việt’s main force, but their initial strategy to swiftly conquer Đại Việt through overwhelming force had completely unraveled. They now faced the prospect of a prolonged campaign and eventual expulsion by Đại Việt forces.
The Yuan troops encountered severe logistical challenges during their campaign. They could not source food locally, as the villagers had buried or hidden their supplies in anticipation of the invasion. The Đại Việt villages resembled tiny fortresses, with tight-knit communities fortified by rivers, fences, and bamboo barriers. Locals set traps, creating hazardous conditions for the Yuan as they entered these areas in small groups, resulting in high casualties. As a consequence, the Yuan soldiers resorted to increasingly brutal tactics, further inciting local resistance. Ethnic minorities also played an active role in the conflict, with some leaders rallying local forces and leveraging the terrain to launch attacks on the Yuan. These efforts exemplified the unity and determination of Đại Việt’s various communities.
In March 1285, Đại Việt divided its forces into two contingents. One was led by the King and the retired King to confront Toghan’s forces from the south, while the other, commanded by Prince Hưng Đạo, consisted of over a thousand vessels heading toward Vạn Kiếp. Although Toghan had stationed troops at Vạn Kiếp, he had to spread his forces thin to maintain control over other regions, leaving him with fewer soldiers at Vạn Kiếp than the Đại Việt. The numerous rivers in the region hampered the Yuan’s ability to gather timely intelligence about Đại Việt’s navy for reinforcements. Consequently, Đại Việt regained control of Vạn Kiếp, enabling them to collaborate with other forces to disrupt Yuan logistics. Nguyễn Thế Lộc’s successful attack and occupation of Vĩnh Bình placed the Yuan’s supply lines in jeopardy.
Despite Toghan’s substantial remaining forces, losing Vạn Kiếp created confusion among the Yuan leaders. They now faced the risk of being attacked from multiple directions. Ariq Qaya sent a letter to Kublai Khan, the Yuan Emperor, requesting reinforcements. At this juncture, if the Yuan attacked the forces of Đại Việt’s King, they could be counterattacked by Prince Hưng Đạo’s troops, leading to a logistics crisis and starvation. Conversely, if they targeted Prince Hưng Đạo, the King’s forces could strike from another direction. With a formidable navy at their disposal, the initiative lay with Đại Việt. The Yuan had no choice but to wait for Đại Việt’s troops to make the next move while awaiting the arrival of Sogetu’s forces for support.
See also: Tran dynasty: the dynasty that defeated the Mongols 3 times
