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[Liu Renyuan and Sun Renshi's bait and switch operation was working flawlessly. They were fishing for the Japanese fleet, and their prey was biting so eagerly they did not stop to consider the danger ahead.
Fearing Zhouliu Castle was about to fall, forty two thousand Japanese troops advanced with no patience and even less planning. Their vanguard was either remarkably brave or staggeringly foolish. The moment they spotted Tang ships, they charged at full speed, rowing their vessels as if their lives depended on it, heading straight for the enemy lines.
Then they collided with the Tang formation and shattered completely.
The river was instantly littered with floating bodies and splintered wood. The brutality of the clash was so overwhelming that the Japanese vanguard lost their nerve on the spot and retreated in panic.
The Tang army did not pursue. They held their position and kept the Baekgang estuary firmly sealed off.
Liu Rengui had anticipated every move from the start. This was the oldest stratagem in military history: "besiege the target to strike the reinforcements." He knew the Japanese would come. He was counting on it. And they walked directly into his trap as if invited.
On paper, Japan had every reason to feel confident. They fielded forty two thousand men against Tang forces in Baekje, which numbered thirteen thousand total, seven thousand Tang regulars and five thousand Silla cavalry. Liu Rengui had split his forces, leaving fewer than ten thousand men to guard Baekgang with the fleet. The numbers were not in Tang's favor; it looked like disaster was imminent.
The next day, the main Japanese force arrived. With their full army assembled, commanders were convinced victory was already theirs. Their confidence soared.
They calculated the figures: forty two thousand against less than ten thousand. An easy win.
They counted the vessels: eight hundred Yamato ships against one hundred seventy Tang warships. No contest.
Japanese generals addressed their troops with swagger. "If we charge together as one, the Tang will surely flee in fear!" they declared.
The advantage seemed undeniable.
Emboldened by their numerical superiority, the Japanese fleet surged forward without hesitation, only to be brutally repelled by the unyielding Tang formation.
Japanese crews rowed furiously, striving to close the distance for boarding actions. But when they drew near enough to see clearly, a horrifying truth dawned on them: Tang warships were enormous. Ramming them with small wooden vessels was like throwing eggs at a brick wall, utterly ineffective.
To make matters worse, Tang ships wielded weapons the Japanese had never imagined. Giant siege engines smashed fragile Japanese craft to pieces from a safe distance. It was not a battle. It was target practice.
Japanese soldiers who fell into the water were helpless. Tang ships were too tall to climb, leaving them to swim aimlessly while archers picked them off from above, like shooting fish in a barrel.
Once the initial charge collapsed, the one hundred seventy Tang warships split into two groups and executed a textbook flanking maneuver, encircling all eight hundred Japanese vessels.
The Tang fleet formed an impenetrable net, forcing Japanese ships to crowd together in the center. Then, taking advantage of wind direction, Tang soldiers unleashed fire arrows and oil bombs.
Japanese commander Echi no Takutsu flew into a rage and charged to the front lines, hoping to boost morale by engaging a smaller Tang ship in close combat. According to the Nihon Shoki, he struck down more than a dozen enemies before a Tang warrior stepped forward, swinging his blade in one clean stroke that cut the commander in half, armor, sword, and all. Game over.
With their ships ablaze and their commander fallen, the Japanese army descended into total chaos. Soldiers jumped into the water and drowned. Their vessels were packed so tightly they could not turn to escape, leaving them to watch as flames spread from ship to ship.
Thick smoke blackened the sky; flames danced across churning waves. Over four hundred Japanese warships became floating bonfires. According to Chinese records, ten thousand Japanese troops perished in the battle, the entire expeditionary force wiped out in a single engagement.
Seeing their reinforcements reduced to ash, the Baekje restoration army trapped in Zhouliu Castle knew surrender was their only option. At that moment, the kingdom of Baekje was officially erased from history.
Four battles. Four victories. Four hundred ships burned. Smoke reached the heavens, and the sea turned red. The enemy was crushed.
How does the Old Book of Tang record this monumental battle? In just twenty one Chinese characters, short, concise, and perfectly in keeping with the style of Chinese historical records.
Just another ordinary, unremarkable great victory. Nothing worth special mention.
Yet viewed in the broader context, this battle was transformative.
In the short term, it settled once and for all who ruled East Asia. The Tang Dynasty stood as undisputed master of the region.
In the long term, it violently reshaped Japan's future. It was the kingdom's worst defeat in premodern history; state sponsored deployments to Korea would not occur again for over nine hundred years, until Hideyoshi's invasions in the late sixteenth century. Terrified of potential Tang or Silla attacks, the Yamato court spent the rest of the 600s building massive coastal fortifications, establishing frontier guards and signal fires on Tsushima, Iki Island, and northern Kyushu, and constructing water fortresses and ramparts across western Japan. The fear was profound and long lasting.
For Baekje, the battle delivered the final blow to any hope of revival. Many fled to Goguryeo or Japan; Baekje royalty who escaped to Japan were granted ranks and titles in the Yamato court, while refugees received citizenship or artisan status.
And Liu Rengui, in every sense, became the first man in history to completely destroy a Japanese invasion force. Not bad for someone who was once considered as good as dead.]
Blinking slowly, Zhuge Liang felt as if he had just unlocked a secret to victory.
"Naval warfare is entirely different from land warfare," he said thoughtfully.
"When comparing the two, the number of soldiers matters less than the ships themselves. No, that is not quite accurate. It is the engineering gap that determines everything."
He began to pace, his eyes brightening as understanding settled in.
"Consider the giant ships we used to conquer Jingzhou. If we fought on the Yangtze, a thousand small skiffs could not damage one of our galleons. We would not even need to fire our heavy ballistas. We could simply sail through them and watch them crumble like paper."
The more he visualized the scenarios, the more animated he became.
"And what if those ships were armed not with regular arrows, but with gunpowder powered cannons?"
Zhuge Liang could picture it clearly. If such technology existed, a single vessel could likely annihilate the entire Jiangdong navy in one afternoon. The thought was almost breathtaking.
A tangible, achievable future lay before him. For a moment, Zhuge Liang felt energy coursing through his entire body.
If I can only lay the engineering groundwork in my lifetime, that alone will be enough.
But to achieve this, mathematics was essential, and he knew it would be a long, arduous journey.
Zhuge Liang and Liu Ba had discussed this problem countless times, reaching a sobering conclusion: mathematics was in disarray. It could barely be called a proper discipline, more a collection of disconnected techniques than a solid foundation.
It was like trying to understand a tree by only examining its fruit. Ancient texts like The Nine Chapters on the Mathematical Art or The Arithmetical Classic of the Gnomon and the Circular Paths of Heaven described only the final results, never explaining the underlying principles.
He and Liu Ba were like blind men tracing fruit back to branches. They could touch the leaves, but could not find the trunk.
Yet after witnessing how future generations connected mathematics to science, Zhuge Liang realized something crucial: mathematics must have a single core system, a root structure that unites everything. The problem was that they had no idea how to find it.
They were not alone in their struggle. Zhang Song had recently discovered a lost set of bamboo slips in Shu called The Book on Numbers and Computation, supposedly brought from Guanzhong during Emperor Wu's reign and hoarded by powerful families ever since.
After Zhuge Liang and Liu Ba spent weeks transcribing and correcting the text, they found it was based on The Nine Chapters. The author had clearly attempted to weave these fragments into a unified theory, but had failed to find the right approach.
Later, they obtained two more fragments: Xu Shang's Arithmetic and Du Zhong's Arithmetic. The same frustration was evident on every page. These mathematical experts had all chased the same elusive goal.
Watching Zhuge Liang sigh over the bamboo slips, Pang Tong felt a flicker of anxiety.
He could tell Zhuge Liang had just made another breakthrough in understanding this future knowledge, but Pang Tong could barely follow his train of thought anymore. It was like watching someone solve a puzzle while he was still searching for the pieces.
A sudden wave of competitive fire hit him. Fine, it's just mathematics, right? When I leave today, I am borrowing a set of those scrolls. I will memorize them backward and forward. There is no way I am letting this guy leave me in the dust.. He refused to believe he couldn't crack it!
He was going to fight for the honor of the Fengchu title.
The man was about to become the world's first competitive mathematician..
Inside the Ganlu Hall.
The moment Li Shiji saw Liu Rengui's battle record, his first thought was: Crap.
There goes my chance at commanding the navy… And sure enough, his fears were justified.
Li Shimin wasted no time. He stepped forward and placed a firm hand on Liu Rengui's shoulder.
"Zhengze, how would you feel about trying your hand at naval command?"
Li Shimin was a master of political persuasion. In modern terms, this was a perfectly crafted pitch, designed to seal the deal.
"Goguryeo is like a ravenous wolf," he began, setting the stage. "They raid our borders and refuse submission. Baekje and Silla are two faced rats, bowing to Goguryeo while claiming to be our vassals, yet secretly colluding with Japan."
He painted a grim picture, ensuring everyone grasped the stakes, then laid out the worst case scenario.
"If we do nothing, Goguryeo will likely swallow Baekje and Silla whole. Once they unify the peninsula, their ambition will know no bounds. They will set their sights on the Central Plains."
"If they seize Baekje's former territory, they won't even need large ships. Small vessels will suffice to raid Hebei in the north and Jiangzhe in the south. Coastal piracy will spiral out of control, and our soldiers will be worn thin just keeping pace."
Liu Rengui's expression grew serious. He was beginning to read the maps clearly now, and after processing his shock about the future, he had to admit the Emperor's prediction was disturbingly plausible.
"However!" Li Shimin's tone shifted abruptly, becoming bold and commanding.
"We already have naval forces training in Liuqiu. Once ready, we can project power across the seas. The only issue is this: our Great Tang has no shortage of excellent generals who lead on horseback."
He paused for dramatic effect.
"We are desperately in need of men who can command from the deck of a warship."
The implication was so clear it might as well have been spoken outright. Adrenaline surged through Liu Rengui's veins, and he dropped to one knee almost instantly.
"I request permission to deploy to Liuqiu, to pacify unrest and expand our borders! I am willing to join the navy to crush pirates and secure our seas!"
After all, if the screen spoke the truth, his original fate was harsh: he would spend half his life as a mid level bureaucrat, offend a corrupt chancellor, be exiled to Korea, and only then make his name through sheer luck. One misstep, and he would die in obscurity.
Since that was his path anyway, why not embrace the navy now? Perhaps he really was meant to be an admiral.
Li Shimin nodded with deep satisfaction. Mission accomplished.
He smiled warmly and helped Liu Rengui to his feet.
"Zhengze, your loyalty and noble spirit do honor to the empire."
If one ignored the deeply bitter look on Li Ji's face standing just beside them, it was a perfect portrait of harmony between ruler and minister.
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[In hindsight, the Tang Dynasty's dominance over its neighbors in its early years stemmed largely from a technological generation gap.
Mingguang Armor and the Tang Dao sword were prime examples, and the same principle applied to their warships. First and foremost, there was an insurmountable gap in scale and safety.
Based on Tang ship remnants excavated today, standard vessels were nearly twenty meters long, with a width of five to six meters. Furthermore, they universally featured watertight bulkheads.
Even if a Japanese warship executed a suicidal ramming attack, it would only breach one or two compartments, posing no threat to the ship's overall structural integrity.
Then there was the staggering disparity in firepower. And the absolute peak of Tang naval engineering was this masterpiece:
The Five-Deck Tower Ship.]