Chapter 15: Yelü Aboqi
Da In-seon led the central army, while Eulbu and Aruji commanded the left and right wings, respectively, as they advanced toward the Khitan encampment where Yelü Aboqi had stationed his troops.
During this maneuver, Da In-seon ordered Daemun-jin's subordinates, brought along from Buyeo Fortress, to beat the drums.
And not just softly—he had them strike the drums loudly enough for Yelü Aboqi to hear. This was a clear display that the forces belonged to the Crown Prince of Balhae.
Naturally, the sound carried even to the Khitan remnants' camp, and Yelü Aboqi immediately sent men to locate the source.
"So, the enemy's commander has come in person. I will cut his head off and savor every bit of him," Yelü Aboqi said, his voice filled with deadly intent.
He responded quickly, leading his ten thousand cavalry and infantry to gradually advance toward the four thousand central troops under Da In-seon.
At first glance, Da In-seon's army seemed small and unimpressive. Yet these were Goguryeo armored cavalry, each fully outfitted. Even in a head-on clash, they were not easily defeated. Yelü Aboqi had no idea of the full strength of Da In-seon's army.
[Balhae Forces]
Da In-seon: 4,000 heavy cavalry (central army)
Eulbu: 3,000 heavy cavalry (left wing)
Aruji: 3,000 heavy cavalry (right wing)
Reinforcements – Daemun-jin: 30,000 infantry
[Khitan Remnants]
Yelü Aboqi: 10,000 light cavalry, 10,000 infantry
Finally, even from a distance near Buyeo Fortress, Yelü Aboqi could make out Da In-seon's forces. To his eyes, they numbered only a few thousand. Then what had caused that booming drum sound? A large army would have made sense—but not a mere few thousand. It seemed like a force meant for a surprise attack, not a frontal display.
Yelü Aboqi was initially dumbfounded. He knew that the Balhae Crown Prince was young, but he couldn't believe he would make such a foolish move.
"Is that all?" he muttered.
"Even so, these are heavy cavalry. Surely the young prince brought only his elite units for protection," one aide replied.
The aide's words eased Yelü Aboqi's doubts slightly. Though the numbers were few, these heavy cavalry could still strike a serious blow against his forces.
Indeed, Da In-seon's troops were of exceptional quality. From appearance alone, a frontal clash would likely inflict serious losses on the Khitans. Yet to an outside observer, it seemed that Da In-seon's confidence in winning with only three thousand heavy cavalry bordered on arrogance.
Recalling the loud drums and the prince's young age, Yelü Aboqi dismissed any suspicion of trickery. He underestimated Da In-seon completely, issuing commands without properly scouting the enemy's strength.
"Our losses will be significant, but in a head-on battle, we will not falter. Capture the Balhae Crown Prince alive! Go, warriors of the steppe! Wash away the bloody grudge with his head!"
With this, Yelü Aboqi boosted his army's morale. At this moment, he had no inkling that he would soon be the one mocked.
And that mockery began with Da In-seon.
Positioning his horse just out of the Khitan archers' range, Da In-seon fixed his gaze on Yelü Aboqi.
"Are you listening?"
"What?"
"You are Yelü Aboqi of the Khitan?"
What had begun as a mere glare quickly turned into an unmistakable sneer. Da In-seon's cold, emotionless eyes conveyed disdain, as if Yelü Aboqi weren't even worth consideration. The faint curl of his lips mocked the Khitan leader openly.
His body twisted and gestured provocatively, refusing to engage in any formal dialogue—his intent was purely to ridicule.
Yelü Aboqi's anger surged, yet his archers were positioned far behind the lines, leaving him unable to retaliate immediately. Da In-seon, fully aware, deliberately provoked him further.
"I am the Balhae Crown Prince! And here you are, Yelü Aboqi, showing your face—such boldness for a boy whose blood isn't even dry yet!"
"You ungrateful worms, babbling nonsense! You steppe villagers who forgot Goryeo's grace and clung to Tang! Do you even know?"
Before escalating the provocation, Da In-seon recalled the contents of a letter sent by Osodo:
"Why would the Tang suddenly attack you, whom you trust?"
Fuelled by resentment and a desire for revenge, Da In-seon abandoned all restraint, laughing heartily at Yelü Aboqi.
"What nonsense are you spouting?"
"When we lightly roasted the Tang's mercenary forces, they promised to obliterate you! So your current state is entirely my doing! Hahaha! I thought I came for revenge, but all I see are clueless chickens! Everyone, enjoy a good laugh at them!"
As the young prince doubled over in laughter, the central army hesitated briefly, unsure how to react. Then, one soldier began laughing, followed by the rest, until the entire central army mocked the Khitan forces. Yet even while laughing, their spears were firmly in hand, ready to strike.
Yelü Aboqi and his troops struggled to contain their outrage. Their tribe had been humiliated, their forces shattered, and all of it was apparently the doing of a young, bloodless boy.
This small, audacious prince had shattered Khitan pride. For Yelü Aboqi, destined to one day unite the Khitans and establish the Liao dynasty, it was unbearable.
"Leave not a single one alive! Capture the prince and slaughter the rest!"
"Show your strength, descendants of Goryeo! Prove it to the steppe villagers!"
Yelü Aboqi's Khitan forces charged, intent on the Balhae Crown Prince.
The Balhae cavalry of four thousand moved forward to meet them.
Da In-seon brandished a massive spear-like weapon, similar to an eoulwol-do, leading the central army into battle.
The clash between Balhae heavy cavalry and Khitan light cavalry began. Though outnumbered, the Balhae forces held a clear qualitative edge. Most of the heavy cavalry were Malgal, like the Khitans, and their reinforced armor, improved with Da In-seon's knowledge of the future, was nearly impervious to the Khitan weapons.
Clang! Clang! Whoosh!
The first casualties fell among the Khitan remnants. Poorly equipped, many were impaled on Balhae spears. Some Balhae soldiers even tossed the skewered bodies into the air to intimidate their enemies.
"They're no longer human. Demons must be slain. No doubt about it," Da In-seon told himself, striking down foes from horseback.
Trained rigorously from childhood under Balhae and Malgal commanders, Da In-seon's body was unusually strong for his age. That experience ensured he could overpower the Khitan cavalry, tossing them from their mounts and piercing through them.
Thunk! Thunk!
Seeing the Crown Prince cut down countless enemies, the morale of his troops soared. Even the central army, initially using Khitan bodies to intimidate, were now inspired by Da In-seon's ferocity.
Despite being outnumbered five to one, the four thousand central troops held the line against twenty thousand Khitan forces.
"I will kill the one who ruined my dream," Yelü Aboqi thought, clenching his sword.
In original history, he would have unified the Khitans, executed dissenters, and established the Liao dynasty, eventually annihilating Balhae. But now, his dreams had been shattered before they even began, thanks to Da In-seon.
Yelü Aboqi's sole focus became revenge.
"There! Capture the Balhae Crown Prince! Fire arrows!"
Already consumed by vengeance and blinded by rage, Yelü Aboqi gave the worst possible orders.
"Your Highness! They aim to fire arrows at their own soldiers!"
"Let them fire! Duck when they come!"
A Balhae commander noted the Khitan order and relayed it to Da In-seon, who merely told his troops to duck.
Amid the rain of arrows, the Khitan projectiles failed to penetrate the restored Goguryeo heavy cavalry armor. Only Khitan soldiers fell, while the Balhae troops remained unscathed.
"The armor may have cost a fortune, but it's worth every penny. Not a single arrow penetrated—a testament to their lack of training," Da In-seon mused.
Seeing this, Yelü Aboqi's fury boiled over.
"I will kill you myself!"
"Be careful, looks like someone's angry! Retreat, men! He's furious!"
Da In-seon, having successfully provoked the Khitan forces and inflicted damage, now began a tactical withdrawal toward Buyeo Fortress.
Yelü Aboqi pursued aggressively, but half of his ten thousand cavalry had already fallen, and the remainder was exhausted from fighting Da In-seon's elite heavy cavalry. Even the Khitan infantry at the rear hesitated, questioning whether to engage after witnessing their leader's brutality.
On the other hand, Da In-seon's forces retained nearly all their strength, aside from thirty casualties and a few fallen horses.
The battle was effectively over. Only surrender or retreat remained, but a furious Yelü Aboqi chased after Da In-seon, intent on killing him.
Soon, however, he began hearing cheers erupting from all directions.