"Those Heuksu bastards… truly have no sense! They dared to oppose someone they shouldn't have. Still… thanks to their stupidity, no one will ever question our loyalty. Not bad at all."
"We only act on the orders of the Crown Prince! Whenever Your Highness commands, we, the brave Malgal—no, the soldiers of Balhae—will rise to support you!"
The Malgal chieftains began offering their troops to Dae In-seon. Unlike nobles merely lending their personal guards, this was a full incorporation of their forces into the Balhae army.
"It is said that the Heuksu Division was arrogant even during the reigns of King Mu and King Seon! This is the perfect opportunity to crush them thoroughly and prevent future trouble!"
"Indeed! Even during the Goguryeo era, the Heuksu were not particularly loyal. Now is the time to punish them properly and establish Balhae's discipline!"
"Subjugate the Heuksu and bring stability to the north!"
"The Khitan are already restless; it is only right that we first eliminate the Heuksu and then strike at them!"
Even the Balhae officials largely supported Dae In-seon's plan.
Despite recent internal noble conflicts, they understood that the Malgal made up a substantial portion of the population. With the Crown Prince successfully integrating six out of the seven divisions, it made sense to target the remaining Heuksu and channel any lingering unrest outward.
For this campaign, Dae In-seon planned to act as commander-in-chief. He would lead 10,000 troops from the central forces stationed in the Upper Capital and 30,000 Malgal soldiers from the six divisions. A total of 40,000 soldiers would march north to subdue the Heuksu.
Before engaging, however, he sent envoys to the Heuksu once more, sternly ordering them to return to the capital. Though the tribe had bowed to Balhae a few times, they still resisted direct authority. Refusal now created the perfect justification for a punitive campaign.
No foreign power could intervene. The southern states were only beginning the Later Three Kingdoms period, Tang had already fallen into decline, and Balhae's army was far stronger in comparison. For anyone to defy Dae In-seon at this point was sheer madness.
"Damn it… the population will drop again. Idiots… they're asking for war."
Dae In-seon bit his lip, his expression contorted with the bittersweet tension of anticipation.
Naturally, population was vital to his vision for Balhae. The Heuksu held considerable numbers, and a campaign there would inevitably cause casualties.
May 892
Bearing these thoughts, Dae In-seon led the 40,000-strong Balhae army north, receiving prayers for victory from the populace as they departed the Upper Capital.
"Ah… I never thought I'd have to lead personally."
In history, there are almost no records of Dae In-seon, not even his birth year. The historical Dae In-seon, as far as records show, only engaged the Khitan once with success. The full integration of six divisions and the subjugation of the Heuksu were not part of recorded history.
If he were that capable, he wouldn't have lost so easily against the Khitan. Moreover…
Dae In-seon glanced back.
The Balhae army followed in perfect order, a far larger force than when they first departed the Upper Capital. Now, 50,000 soldiers marched north—many volunteers from local districts still bearing resentment toward the Heuksu.
Though trained in martial arts, the body within Dae In-seon was still the one from peaceful modern Korea. Hunting had been enjoyable, but the reality of leading men into battle, the thought of killing, and the fear of dying… all made his heart race.
"Ha… life, really."
"Hahaha! Your Highness! I never imagined I'd join such a glorious expedition alongside Your Highness! My heart beats so strongly—I'm honored! Are you not exhilarated, Your Highness?"
"Ah… yes. I'm trembling too… in many ways."
The Malgal chieftains, oblivious to the burden of war, were cheering their participation. Dae In-seon couldn't help feeling resentment toward their naive enthusiasm.
This campaign… is unavoidable.
The Heuksu, or Blackwater Malgal, had moved south during Balhae's troubled years. Their actions had strained Balhae's resources but never toppled the state. Subjugating them now served a legitimate purpose: the stabilization of Balhae.
One week later, Dae In-seon's forces reached the Heuksu's territory along the Amur River.
The army had originally intended to advance quickly with cavalry at the forefront, but reinforcements from surrounding districts swelled their numbers, causing slight delays. Yet the locals' grievances toward the Heuksu meant the timing was perfect. Crushing them would gain the support of the region's administrators and populace, who would become Balhae soldiers under Dae In-seon's command.
Before engaging, Dae In-seon spoke to Eulbu, who silently followed him.
"You may sit this battle out if you wish. I will not hold it against you."
"The misdeeds of our own tribe forced this. I, too, must take part in subduing them."
Indeed, Eulbu would be striking his own kin. Yet, with Dae In-seon determined to fully integrate the Malgal under Balhae's rule, Eulbu was now fully a Balhae subject. The campaign could be seen as a suppression of rebels, not a slaughter of kin.
"Very well. Speak if it becomes too much."
Though Dae In-seon felt a pang of guilt, he respected Eulbu's resolve.
Scouts soon reported that Heuksu troops were stationed along the riverbank.
"Your Highness, how should we proceed? They have positioned their forces near the Amur. Shall we strike?"
Hesitation here could be risky, yet outright cruelty would brand Dae In-seon a ruthless ruler. Showing even a hint of uncertainty now demonstrated humanity without weakening authority.
"What do you think? Will they heed our words if we order it?"
"If they would, would they oppose us with troops?"
Dae In-seon had to decide. Unlike a dramatic hero in historical dramas, he could not afford to embrace everyone and lead blindly. Balhae's survival depended on tough decisions. Any delay risked the Heuksu rising again, while the Khitan remained a lurking threat. The Heuksu's existence consumed both manpower and resources.
Moreover, they had had several chances to comply—under both King Mu and King Seon. Repeated opportunities had been ignored. Dae In-seon's decision was clear.
"Prepare for a decisive strike!"
"We will annihilate them. How many troops?"
The accompanying chieftains' voices confirmed readiness. Dae In-seon reviewed the enemy's strength.
At most, he estimated 10,000, possibly 20,000 if fully mobilized. Yet caution was necessary. These were the ancestors of the Wanyan, founders of the Jin and later the Qing dynasty. Their combat power could not be underestimated.
"10,000. More than enough to crush them. What shall we do with the Heuksu civilians?"
This is for Balhae, but also for me. I am no hero. I cannot allow those who might betray us to survive. Centuries of tolerance have ended.
"Their defiance is not the act of a single chief. Spare those willing to submit and become Balhae citizens. All others, execute."
Some hesitated, taken aback by Dae In-seon's resolve. Yet the mandate was clear. The battle about to begin would be hell for the Heuksu.
The Heuksu struck first. Cavalry surged forward in a fierce charge.
Balhae responded with 3,000 cavalry and 7,000 infantry. The army did not reveal its full strength, only matching the enemy in numbers to avoid intimidating them.
To the mostly cavalry Heuksu, this small force seemed laughable, provoking their attack.
Even the chieftain-turned-generals of Balhae grumbled.
"Your Highness, why not crush them in one stroke?"
"I intend to minimize our casualties while breaking their morale completely. Hence, only 10,000 face them initially."
The chieftains muttered in frustration. Dae In-seon paused, weighing whether to reveal the full strategy. Finally, he shared his plan.
"These 10,000 are the maximum we could draw from Heuksu at this moment."
"And that means?"
"We intend to defeat them with a smaller force, lowering their morale."
The generals speculated among themselves, yet none grasped the full scope of Dae In-seon's strategy.