"The Tibetan Kingdom defeated the Tang Dynasty? Are you sure, Kongming?"
Zhang Fei scowled, looking genuinely skeptical.
He hadn't forgotten the historical records surrounding the An Lushan Rebellion, where Tibetan armies had practically treated the Tang borders like their personal piggy bank. But surely, at the height of the Tang's military power, the Tibetans wouldn't have been foolish enough to provoke the tiger?
Zhuge Liang didn't take offense at the interruption. He waved his feather fan and chuckled.
"Think about it, Yide. If you were the King of Tibet and wanted to expand your borders, which route would you take?"
"Me...?"
Zhang Fei furiously stroked his beard, his mind churning for an answer.
"I would follow the strategic genius of Lü Bu and An Lushan! I would march straight to Chang'an and beg Emperor Gaozong and Empress Wu to adopt me as their godson! Then, using Sima Yi's playbook, I would secretly train an elite death squad and wait for the perfect—"
"Stop, stop, stop!"
Zhuge Liang groaned and massaged his temples. He lightly tapped Zhang Fei's head with his fan.
"Enough with the jokes!"
"Fine, fine. Let me actually think."
Zhang Fei looked slightly offended. His strategy was basically a collection of history's greatest traitors. Why wouldn't it work?
Slipping back into his serious commander's demeanor, he studied the topographical map projected behind them. After a moment, he nodded.
"If they want to expand, they really only have one option: push through the Qinghai region and strike directly at the Hexi Corridor."
The map was simplified, but the geography was undeniable. The Tibetan Plateau was surrounded on all sides by towering mountain ranges. The only viable exit was a massive gap to the east. Following that gap led directly to the Qinghai Lake region. Pushing farther east from the lake would place an army right at the gates of the vital Hexi Corridor.
Zhuge Liang nodded approvingly.
"For Tibet, securing Qinghai is a geopolitical necessity. The region is currently occupied by the remnants of the Tuyuhun Kingdom, which the Tang previously shattered, as well as various Tangut tribes that harbor deep resentment toward Chang'an. Tibet will inevitably mobilize its forces to conquer that territory. If the Tang fails to establish defensive positions, I am afraid..."
Zhang Fei scratched his head.
"Wait, so the Tuyuhun are like... a fence? A really important fence the Tang built?"
"Exactly," Zhuge Liang said. "A fence that keeps the Tibetans locked in their own mountains."
"So what happened? Did the fence break?"
"The fence rusted," Zhuge Liang replied. "Li Zhi forgot to maintain it."
Zhang Fei blinked.
"So the Tang lost because someone forgot to paint the fence?"
"It was a very important fence."
"And Li Zhi just... forgot?"
"He was busy fighting Goguryeo."
Zhang Fei threw up his hands.
"So the Tang lost a whole empire because Li Zhi was too focused on one enemy and ignored another? That is like... that is like me fighting Cao Cao and forgetting Wu exists!"
"That is essentially what happened."
Zhang Fei stared at him. "And people say I am the dumb one?"
"Yide, history remembers many things."
"Such as?"
"Your drinking habits."
"That has nothing to do with this conversation!"
"Precisely."
[Lightscreen]
[To understand why Tibet and the Tang eventually became bitter enemies, we first need to understand one simple fact: Tibet's national strategy revolved entirely around the Qinghai region.
This was not because the Tibetans had a particular obsession with Qinghai, but because geography left them with very few alternatives.
The Tibetan Plateau was surrounded by mountains on nearly every side, and the Qinghai corridor was the most practical route connecting Tibet to the outside world.
If Tibet wished to expand its influence, develop trade, or project military power beyond the plateau, it first had to pass through the Tuyuhun Kingdom.
That is precisely why Tibet first appeared on the Tang Dynasty's radar.
In 637 CE, Emperor Li Shimin received an urgent diplomatic report from Tuyuhun.
If we translate the message into modern language, it essentially said, "Dad, someone is beating me."
Now, here is the context.
Tuyuhun was already a Tang vassal state. Li Shimin had personally strengthened the relationship through a marriage alliance, sending Princess Honghua to marry Tuyuhun's ruler, Murong Nuohebo.
From the Tang court's perspective, this was not merely a conflict between two neighboring states. It was an attack on one of its own dependents.
Before Li Shimin could even dispatch officials to investigate, another piece of news arrived. In 638 CE, Tibetan forces brazenly crossed the border and invaded Songzhou.
Li Shimin's response was immediate.
He mobilized fifty thousand troops and assembled an impressive roster of commanders, appointing Hou Junji as supreme commander, while Zhishi Sili, Liu Lan, and Niu Jinda each led separate forces.
The objective was simple: beat Tibet and rub their faces into the ground so thoroughly that it would never forget the experience.
As it turned out, the campaign was decided almost before it had begun.
Niu Jinda, a veteran who had followed Li Shimin since his early campaigns, launched a rapid night attack and caught the Tibetan vanguard completely unprepared.
According to the Old Book of Tang, the Tibetan army was utterly routed, suffering enormous casualties.
Having never encountered Tang heavy cavalry before, the Tibetans suddenly realized that they had picked a fight with an opponent far more dangerous than they had anticipated.
Their surrender came with remarkable speed.
They returned occupied territory, released captives, and sent their top diplomat, Gar Tongtsen, to Chang'an bearing gold, treasures, and a formal apology.
While he was there, he also politely requested a marriage alliance.
This was not an act of weakness but one of political pragmatism.
Songtsen Gampo was an exceptionally capable ruler who understood both the limits of his kingdom and the value of peace.
As long as he remained alive, relations between Tibet and the Tang Dynasty remained remarkably stable.
Li Shimin, meanwhile, understood something equally important. The Tuyuhun Kingdom was more than a tributary state. It was a strategic buffer that effectively locked Tibet inside the plateau.
Whoever controlled Qinghai controlled the routes linking the Central Plains, the Western Regions, the northern steppe, Tibet, and southern Gansu.
Every major western campaign undertaken by Li Shimin relied on this corridor, and by the late Zhenguan era it had become one of the most important arteries of the Silk Road.
For that reason, Li Shimin watched Tuyuhun carefully. Whenever signs of instability appeared, he intervened quickly, and whenever support was needed, he provided it.
The buffer had to remain intact.
Unfortunately, matters changed during the reign of Emperor Li Zhi.
After Songtsen Gampo died in 650 CE, the throne passed to his one-year-old grandson, Mangsong Mangtsen, leaving real authority in the hands of Gar Tongtsen, the same diplomat who had once traveled to Chang'an bearing apologies and gifts.
Ambitious and highly capable, he had spent years observing the Tang and had no intention of allowing Tibet to remain confined within its mountains forever.
At the same time, the elderly Murong Nuohebo sent increasingly desperate requests for aid to Chang'an.
However, Li Zhi's attention was fixed on Goguryeo.
As the appeals continued to arrive unanswered, the strategic buffer that his father had carefully maintained began to weaken, while Gar Tongtsen patiently waited for the opportunity to strike.]
Hou Junji lifted his head, only to find Zhangsun Wuji wearing a radiant smile that practically screamed I told you so.
"The Duke of Liguo truly has unfortunate timing," Zhangsun Wuji said with deep, utterly fake sympathy. "Every great battle somehow begins only after you leave."
For one brief, violent moment, Hou Junji considered demonstrating to the court why generals were traditionally armed.
The bullying was becoming intolerable.
He began to seriously wonder whether he had exhausted his entire reserve of luck at Xuanwu Gate. The Light Screen was supposed to be a heavenly blessing. Yet after sitting in Chang'an for months watching these broadcasts, his historical legacy had somehow been reduced to occasional cameos and footnotes.
Worse, the moment he failed to personally appear on a battlefield, a war significant enough to shake an empire immediately broke out. If he had commanded the campaign against Tibet instead of Niu Jinda, perhaps he could have accumulated enough merit to bargain his way out of his future execution.
The more he thought about it, the more tragic his life seemed.
Li Shimin, however, paid no attention to Hou Junji's inner suffering.
Hearing the narrator praise his geopolitical foresight, he slowly nodded and stroked his beard.
"This future descendant has some talent."
The hall fell silent.
"It seems he has managed to grasp perhaps twenty or thirty percent of my intentions."
Li Jing's mouth twitched. Du Ruhui lowered his head. Even Fang Xuanling suddenly found the floor very interesting.
Li Shimin continued with complete confidence.
"Although, I must admit, his analysis of the Qinghai strategy is quite excellent."
Zhangsun Wuji blinked.
"Your Majesty… are you taking notes from someone who only understands twenty percent of your thinking?"
Li Shimin's hand paused.
"Naturally not."
The Emperor quietly folded the piece of paper he had been writing on and slipped it into his sleeve. No one said a word.
Simultaneously, Li Shimin focused his eyes, mentally recording every single detail of the narrator's analysis. He fully intended to corner Du Ruhui later that night, force the Chancellor to transcribe the entire broadcast, and study it intensely.
Li Jing discreetly rolled his eyes, but his blood was already pumping. The Light Screen's strategic assessment mirrored his own tactical theories perfectly. Now that the Tang possessed the ultimate foresight, they could launch a preemptive strike and hand the Tibetans a terrifying surprise!
Fang Xuanling stepped forward, outlining a diplomatic and economic approach.
"We must reinforce the Qinghai Lake chokepoint to permanently sever Tibet's eastward expansion. Once the border is secure, we can open heavily regulated trade markets."
Having seen the horrific devastation the Tibetans inflicted on the Hexi Corridor during Zhang Yichao's future timeline, Fang Xuanling refused to let that economic juggernaut burn.
Du Ruhui completely agreed with his old friend, offering a highly systematic solution.
"The broadcast clearly states that even when Tibet launched a full-scale invasion eight years from now, they were instantly crushed by our vanguard forces. Their current military strength is entirely negligible."
"Rather than forcing an exhausting military occupation in the high altitudes, we should establish an impenetrable blockade. Better yet, we can use heavy financial incentives to weaponize them against the Western Turks."
Understanding just how fragile Tibet's current military was, the Tang court's collective anxiety evaporated. They were just another flavor of Turkic nomads living on a very tall mountain.
Li Shimin nodded, integrating both Chancellors' advice into his planning. He then focused on the "crack" in the armor mentioned by the screen.
"I suspect... once my son Li Zhi successfully annihilated the Western Turks, he mistakenly believed the entire western theater was permanently pacified. His eyes became entirely fixated on the only target I failed to conquer. Goguryeo."
[Lightscreen]
[The Tuyuhun Kingdom was the ultimate insurance policy Emperor Li Shimin personally drafted to protect the Hexi Corridor.
However, because Emperor Li Zhi failed to appreciate its strategic value, that insurance policy was brutally canceled by the Tibetan Chancellor, Gar Tongtsen.
Now, let us understand who Gar Tongtsen really was. He was the same diplomat who had traveled to Chang'an in 640 CE bearing gold and apologies. He had stood before Li Shimin, witnessed the power of the Tang court, and studied its weaknesses. After Songtsen Gampo died in 650 CE, Gar Tongtsen became the real power behind the Tibetan throne, ruling as regent for the infant emperor Mangsong Mangtsen. He had spent years preparing for this moment.
Just as Emperor Li Shimin aggressively exploited a narrow geopolitical window to conquer Gaochang, Gar Tongtsen perfectly timed a window of extreme Tang distraction.
In 655 AD, Su Dingfang was appointed supreme commander to invade Goguryeo. This marked the beginning of Emperor Li Zhi's grueling, fourteen-year war in the east.
The very next year, in 656 AD, Gar Tongtsen launched a massive strike and conquered the Bailan Qiang tribes. By 660 AD, using the Bailan territory as a forward operating base, Tibet began systematically devouring the Tuyuhun.
In August 660, the Tibetans launched their full-scale invasion. The Tuyuhun king, Murong Nuohebo, fled north and sent desperate pleas to Chang'an. But the Tang court was busy. They had just dispatched a massive force to the Korean Peninsula to destroy Baekje. There were no troops to spare. The request for aid was rejected.
Furthermore, Gar Tongtsen actively engaged in geopolitical warfare to stretch the Tang military thin. He intentionally agitated the western borders to slow down the Tang offensive in Liaodong, creating a smokescreen for his annexation of the Tuyuhun.
In 662 AD, Tibet formed a loud, heavily publicized military alliance with the Gongyue tribes. They openly declared a rebellion against the Tang. Forced to respond, Emperor Li Zhi deployed Su Haizheng to crush the uprising.
Gar Tongtsen looked at the approaching Tang imperial army and essentially shrugged.
He sent a message: "Give us a massive pile of money and grain, and we will cancel the rebellion. If you refuse, we will simply retreat into the mountains and wait for you to leave. Then we will rebel again."
Su Haizheng's troops were exhausted from the long march. He chose not to engage. He paid the extortion money to buy peace. It was a humiliating decision, but he had no choice.
Realizing the Tang court was desperate to avoid a two-front war, Gar Tongtsen accelerated his plans. He began flooding Chang'an with contradictory diplomatic messages to completely paralyze Emperor Li Zhi's decision-making process.
In the summer of 663 AD, the conflict reached its climax. The Tuyuhun, battered and bleeding from relentless Tibetan assaults, sent desperate envoys to Chang'an. They claimed their kingdom was on the verge of total annihilation and begged for immediate military intervention.
Simultaneously, Gar Tongtsen dispatched his own envoys to Chang'an. They claimed the Tuyuhun were aggressively invading Tibetan territory! They demanded the Tang Dynasty deploy troops to punish the Tuyuhun and uphold justice!
Here is the tragic detail. The Tuyuhun king had a minister named Su Hegui. He defected to the Tibetans and revealed the Tuyuhun's defenses. The Tibetan army launched its final assault. The Tuyuhun army was disastrously defeated.
Emperor Li Zhi was completely confused by the contradictory reports. He chose the worst possible diplomatic solution. He declared neutrality. His official response was: "Neither side shall receive military aid."
In the name of fairness, he abandoned his own ally.
Later that same year, acting on Gar Tongtsen's orders, the Gongyue tribes launched a vicious attack on the Tang protectorate of Khotan, forcing the Anxi Protector-General to scramble troops for a rescue mission.
In 665 AD, Gar Tongtsen built a new coalition with Shule and Gongyue and attacked Khotan again. Once more, Emperor Li Zhi was forced to divert vital military resources to save the city.
The Tuyuhun's desperate cries for help were entirely factual. According to Tibet's own historical records, Gar Tongtsen spent the years between 659 and 666 AD physically inside Tuyuhun territory, personally overseeing the violent assimilation of their nation.
The envoys who arrived in Chang'an in 663 AD were likely the last gasp of the pro-Tang faction within the Tuyuhun government. Tragically, Emperor Li Zhi was too busy to listen.
In 665 AD, fresh off General Li Ji's legendary annihilation of Goguryeo, the imperial court finally debated how to punish Tibet. Once again, Emperor Li Zhi's geopolitical instincts failed him completely.
Minister Yan Liben argued aggressively: "The conquest of Goguryeo did not exhaust the treasury or the populace. Launching a punitive expedition against Tibet is entirely feasible."
General Qibi Heli offered a tactical trap: "If we march a massive army directly at Tibet, they will simply retreat into the mountains. We should publicly deny the Tuyuhun's request for aid, secretly encircle the region with elite troops, and crush the Tibetans in a single, decisive ambush."
Qibi Heli knew what he was talking about. He was a Tiele general who had served Tang for decades, participated in campaigns against Gaochang, Kucha, and Goguryeo. He understood steppe warfare better than anyone.
General Jiang Ke, a direct descendant of the legendary Shu Han commander Jiang Wei, was furious. He bluntly told the Emperor: "The Tuyuhun and the Tang share a relationship of lips and teeth! If the lips are gone, the teeth will freeze! Stop debating tactics and deploy the army immediately to save them!"
Emperor Li Zhi rejected every single proposal.
The Tuyuhun kingdom, which had served as Tang's buffer for decades, was destroyed. The lock rusted. The fence fell. Gar Tongtsen had succeeded where his predecessor had only dreamed. He broke open the western gate of the Tang Empire.
As the old saying goes: "The prodigal son feels no pain when selling his grandfather's land." Li Zhi had inherited a fortress and sold the door for scrap, without even realizing what he had done.]
Li Shimin vividly remembered the Light Screen's broadcasts about the Three Kingdoms.
Back then, he had laughed at Cao Pi countless times. Refusing to listen to your ministers? Ignoring good advice? How does someone become Emperor and still make such foolish decisions?
Never in his wildest imagination had he expected to hear the phrase: Li Zhi rejected every proposal.
"Infuriating. This kid really needs a good beating."
Li Shimin struck the armrest with his palm, startling several ministers.
"This is exactly how an empire destroys its own foundations."
The Light Screen had just confirmed that his entire western strategy had been correct. The Tuyuhun Kingdom was a vital buffer, and the Hexi Corridor was the lifeline of the western frontier.
And his son threw it in the garbage.
The narrator's previous idiom echoed loudly in Li Shimin's mind.
The prodigal son feels no pain when selling his grandfather's land.
He had already made up his mind that after returning to his palace tonight, he would give two-year-old Li Zhi a very good spanking. The child would naturally have no idea why he was being punished, but that hardly mattered.
At the very least, the exercise would ease the Emperor's frustration. It would be Li Zhi's very first contribution to the stability of the Great Tang.
He let out a long breath, forcing himself to calm down.
"Alright. I have made my peace with the fact that my son is an idiot."
Sensing the dangerous shift in the Emperor's mood, Li Ji carefully masked his own excitement and stepped forward, playing the role of the reasonable statesman.
"Your Majesty, we must remember that Goguryeo was the ultimate nightmare of the Tang Dynasty. The future generations only see the glory of your western conquests. They do not understand the sheer blood, sweat, and political capital you exhausted trying to break the east. It is natural that your son's eyes were entirely locked onto Liaodong."
Li Shimin's anger vanished, replaced by a massive, knowing grin.
"Oh, since you put it that way, I assume my beloved General Maogong found the Liaodong campaign to be incredibly difficult?"
He tilted his head.
"Perhaps you should transfer to the naval forces for a few years? We can have you practice by conquering the island of Liuqiu."
Everyone in the room knew exactly what Li Ji was doing.
Emperor Yang of Sui had shattered his empire trying to conquer Goguryeo. Emperor Li Shimin, the greatest military mind of the century, had personally led an invasion and failed.
If Li Ji successfully exterminated the nation that defied two legendary Emperors, his name would echo in eternity. The glory was unimaginable.
Li Shimin was essentially calling his bluff. Oh, you are defending my son's obsession with Liaodong? Is it because you were struggling during your campaign there?
Whatever goodwill Li Ji had left for Emperor Li Zhi vanished on the spot.
"Liaodong is a miserable little kingdom!" Li Ji roared, puffing out his chest. "Why would we need Your Majesty to personally intervene?"
He stepped forward.
"Please allow your humble servant to personally exterminate them and project the terrifying majesty of the Zhenguan era!"
"Emperor Gaozong? Who is that? I do not know the man."
Li Ji was going to cement his legacy as the ultimate war god of the Zhenguan era.