The Urge for Expansion and Revenge
In 1286, the Yuan Dynasty decided to concentrate its efforts on invading Đại Việt, canceling its plans for an attack on Japan after two failed attempts. Kublai Khan addressed his officials, stating, “Japan has never invaded us. Now, Đại Việt has crossed our borders. We must postpone our plans for Japan to address this incursion first.” During the previous war, Đại Việt forces had pursued the fleeing Yuan troops into their territory without occupying any land. Under this pretext, the Yuan sought to refocus their expansionist and vengeful goals. Toghan was appointed as the Commander-in-Chief, supported by notable military leaders such as Ariq Qaya, Ayuruci, and Omar.
However, the situation was not entirely favorable for the Yuan. In the southern regions, there were numerous uprisings as the government struggled to provide sufficient logistics and soldiers for the war. Some officials expressed concern for the plight of the civilians, suggesting that Kublai Khan delay the invasion. A few even recommended negotiating with Đại Việt instead. Consequently, Kublai Khan postponed the invasion once more. Nevertheless, as the situation gradually improved, preparations for the expedition rapidly commenced at the end of 1286.
After their previous defeat, the Yuan focused on strengthening their navy, assembling two fleets of war vessels—one for logistical transport and another for combat. Under Omar’s command, this navy comprised 600 ships and thousands of elite naval soldiers from Hǎinán and Jiāngnán. They aimed to overpower the Đại Việt navy. Despite their formidable forces, Khan cautioned his men, “Do not underestimate Giao Chỉ (Đại Việt) just because it’s small!” To further their strategy, Khan attempted to establish a puppet dynasty in Đại Việt by enthroning the cowardly Trần Ích Tắc as its king. Members of this puppet dynasty were expected to accompany the Yuan troops into Đại Việt. Kublai Khan even issued a proclamation aimed at enticing Đại Việt civilians, criticizing their king and assuring them that only he would be punished, not the populace. He urged civilians to focus on their work instead of preparing for war. However, Đại Việt civilians were already aware of the Yuan’s brutal actions during the first two wars, rendering the proclamation ineffective.
Despite releasing 50,000 prisoners after the battle, the Yuan’s malicious intentions remained unchanged. Đại Việt adopted a conciliatory approach, seeking a long-lasting peace. They sent envoys to escort Ayuruci back to the Yuan, paid tribute, and returned war prisoners. However, to prevent these 50,000 former prisoners of war from launching future attacks, Đại Việt tattooed their faces with markings and warned them that any return to battle would result in immediate execution.
The Yuan, undeterred, continued to push for official rule over Đại Việt, a demand that was met with refusal. Meanwhile, Đại Việt spies uncovered the Yuan’s military preparations in the south. The King realized that another invasion was imminent.
According to Prince Hưng Đạo’s assessment, the previous wars had transformed Đại Việt civilians into warriors and its soldiers into seasoned fighters. In contrast, the Yuan troops were fatigued from their long journey and anxious about potentially repeating past failures. By 1287, the Yuan’s intentions to invade Đại Việt became clear through their military preparations and training. After a brief period of peace, Đại Việt civilians found themselves preparing for war once again. Concerns arose among many, including the King and court members, regarding whether Đại Việt’s military strength had sufficiently recovered. Some advised Prince Hưng Đạo to recruit more soldiers, but he emphasized the importance of quality over quantity, stating, “It’s more important to have well-trained soldiers than to have too many.” He explained that a larger force would require more logistics and training, which could lead to complications in troop movements and deployment. A smaller, well-trained, and experienced force was preferable.
By the end of 1287, Yuan troops under Toghan’s command approached the Đại Việt border, with their navy prepared for deployment. Another war was on the horizon.
The Yuan’s Fear of Đại Việt’s Archery Skills
The Yuan began their preparations in early 1286, but it wasn’t until late 1287 that they organized their forces into various formations for the attack. As their vanguard reached the Đại Việt border, skirmishes erupted between them and the Đại Việt border guards. Due to the narrow passes along the frontier, which were unsuitable for large-scale troop deployments, the Yuan chose to deploy their elite forces to break through using their most courageous soldiers. Learning from previous encounters, Đại Việt utilized the terrain to their advantage, neutralizing the enemy’s numbers.
Led by Bolqadar and Zheng Peng Fei, the Yuan troops navigated the northern mountains quickly but faced fierce resistance in Bắc Giang. Under the command of Trần Quán, the royal palace guards were strategically positioned at the Lãnh Kinh pass, coordinating navy and infantry efforts to block the enemy. As soon as the Yuan soldiers attacked, they were met with a barrage of poisoned arrows from Đại Việt’s troops, resulting in significant casualties and halting their advance. In light of these losses and the realization of the strength of their opponents, the Yuan soldiers and their commanders became increasingly fearful. Bolqadar and Zheng Peng Fei withdrew their troops to Vũ Cao pass and awaited the eastern forces led by Toghan.
Prince Hưng Đạo strategically avoided direct conflict with Toghan’s eastern forces, preserving the strength of his troops for a prolonged engagement. This maneuver allowed Toghan to advance from Lộc Bình to near Vạn Kiếp in just four days, where he encountered Prince Hưng Đạo’s forces positioned near the river and Phả Lại mountain. Learning from past battles, Toghan chose to forego an assault on Thăng Long Imperial City and instead occupied Vạn Kiếp to secure control over crucial areas.
On the other hand, Đại Việt’s strategy remained adaptable, allowing for flexibility in their advances and retreats. However, Prince Hưng Đạo deployed his forces as if preparing for a large-scale confrontation with Toghan, who awaited the arrival of Zheng Peng Fei, Bolqadar, and Omar’s navy.
At this point, the Yuan’s navy, consisting of 18,000 soldiers under Omar’s command, had entered Đại Việt territory. The Yuan navy was divided into multiple fleets to enhance collaboration in the small bays along the coast of Đại Việt. Behind them were several other generals commanding substantial fleets, while another fleet, responsible for logistical transport, was led by Zhāng Wénhǔ. Upon reaching Ngọc Sơn, they encountered resistance from Đại Việt’s navy. Although Đại Việt’s forces were smaller, they managed to confront the Yuan.
Under the orders of Marquis Trần Toàn, Đại Việt forces targeted the last fleets of the enemy, inflicting heavy casualties on Yuan soldiers and capturing many vessels, warhorses, and prisoners. Upon reaching Vân Đồn’s territorial waters, the Yuan navy clashed with Đại Việt’s main fleet led by Prince Nhân Huệ, leading to an intense battle. Initially, the Yuan troops gained the upper hand, forcing the Prince to retreat, which angered Emperor Trần Thánh Tông. He sent an official to summon the Prince for punishment; however, the Prince requested three more days to make amends through his achievements. His soldiers hurriedly prepared, awaiting the arrival of supply vessels.
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The Situation Changes
At the start of January 1288, Toghan took direct command of the troops as they entered Vạn Kiếp. Meanwhile, fleets under Omar and Zheng Peng Fei joined him, bringing their total force to 300,000 soldiers. Prince Hưng Đạo decided to withdraw his forces to preserve their strength, quickly concluding the battle at Vạn Kiếp and temporarily conceding the area to the enemy.
Upon securing Vạn Kiếp, Toghan established his headquarters there to exert tight control over the region. He appointed Líu Yuān to lead 20,000 soldiers, both naval and infantry, in an offensive aimed at gaining control of Hải Đông and limiting the operational space of Đại Việt’s navy. Learning from previous encounters, Toghan fortified two major mountains with wooden ramparts, food warehouses, and barracks. The Yuan forces then aggressively advanced toward Thăng Long and the southern regions of the Red River Delta. In response, Prince Hưng Đạo launched a rear attack, forcing Toghan to call for reinforcements.
Prince Hưng Đạo strategically positioned his forces alongside the Đuống River to defend Thăng Long from the north, while the emperor prepared for a potential retreat. Strong royal guards were dispatched to support Prince Hưng Đạo. This new defensive line provided Prince Hưng Đạo the time he needed to prepare his forces while sustaining minimal damage from the Vạn Kiếp engagement.
Battlefield in the Northwest Region
Prince Chiêu Văn Trần Nhật Duật commanded a diverse force of 40,000 soldiers to establish two defensive lines in the northwest, tasked with protecting the Thăng Long imperial city. Militia groups composed of various ethnic communities in the northwest, organized from Vân Nam into Đại Việt’s territory, played a crucial role in ambushing and harassing the Yuan forces.
The Yuan militia from Yunnan, consisting of a mix of soldiers from various ethnic backgrounds and Mongolian cavalry, arrived in Đại Việt quickly. They appeared stronger than in previous conflicts; however, they faced anxiety due to the sporadic but fierce resistance from Đại Việt’s smaller forces. A significant battle ensued upon encountering Prince Chiêu Văn’s troops, resulting in a withdrawal order from the prince. Generals Lê Thạch and Hà Anh coordinated their forces to cover the retreat of the main army, allowing Đại Việt’s forces to regroup and counteract the Yuan’s movements. Aruq was then tasked with waiting for Toghan’s forces to collaborate with them.
Trần Khánh Dư’s Heroic Act
Trần Khánh Dư predicted that the Yuan’s supply fleet would follow Omar’s navy as they rushed to join Toghan’s troops. Omar underestimated Khánh Dư’s naval capabilities, overlooking two critical factors: the remarkable discipline of Đại Việt’s soldiers and the essential need for adequate food supply for such a vast army. This oversight resulted in Omar’s food fleet becoming isolated.
Gathering the remaining vessels and soldiers, Prince Nhân Huệ strategically positioned his forces in Vân Đồn. The Yuan’s supply fleet, led by Zhāng Wénhǔ, appeared without naval protection and became vulnerable. Once they entered the ambush zone, Đại Việt’s forces launched a sudden and relentless assault from their fighting vessels, decimating the Yuan fleet and resulting in heavy casualties. Zhāng Wénhǔ attempted to retreat inland but found himself trapped, flanked by Đại Việt vessels at Lục Thủy and Vân Đồn. Despite their desperate measures to escape by discarding supplies into the sea, the determined Đại Việt troops managed to separate, annihilate, and capture the Yuan forces. Zhāng Wénhǔ was the only one to escape on a small boat to Quỳnh Châu. Prince Nhân Huệ’s forces seized a significant cache of food, weapons, vessels, and prisoners, marking a great victory to report to the emperor.
This triumph marked a pivotal turning point in the war, disrupting the Yuan’s strategy. While Đại Việt’s forces could continue a prolonged resistance, the Yuan army faced an increasingly dire situation due to dwindling food supplies.
The Yuan’s Continued Arrogance
Despite being unaware of Zhāng Wénhǔ’s crushing defeat and still possessing adequate supplies, the Yuan soldiers remained arrogant and sought to maintain their presence. They captured several of Đại Việt’s bases while continuing to push back against the defensive efforts. Toghan subsequently divided his troops to launch an assault on Thăng Long, leveraging their disciplined tactics and momentum.
In response, Prince Hưng Đạo organized his troops to pin the enemy down and executed ambushes. On January 30th, the Yuan vanguards engaged Đại Việt forces at Đại Than but suffered defeat. They quickly regrouped and advanced toward Gia Lâm, where Đại Việt’s forces lay in wait. Toghan’s troops camped at Gia Lâm, preparing to cross the river and assault Thăng Long. Meanwhile, Đại Việt’s king dispatched an envoy to initiate peace talks, though it was merely a tactic. Toghan dismissed the envoy, unaware of the impending counterattacks.
On February 2nd, 1288, Toghan’s troops crossed the river and attacked the imperial city, facing only a handful of determined defenders who inflicted significant damage before the main army, royal family, and civilians evacuated. Consequently, Toghan swiftly occupied Thăng Long, while Aruq’s waiting troops at Phú Lương pass joined his forces.
Similar to previous strategies, Prince Hưng Đạo decided to leave Thăng Long open and shift his forces south to evade the enemy’s initial strength. With their experiences from earlier conflicts, Đại Việt’s troops efficiently executed attacks, withdrawals, and counteractions against the pursuing Yuan forces, preventing the Yuan from closing the gap.
See also: Tran dynasty: the dynasty that defeated the Mongols 3 times
