Chapter 129: Top-Secret Weapons

As Zhang Pingbo had said, when the Dragon King sets sail, heavy snow is on the way. After a storm, the weather around Qinghai grew colder by the day. The cold wind over the sea cut like knives into people’s faces. On the eighth day of the tenth month, large flakes of snow, as soft as goose feathers, began to fall—the first snow of the seventh year of Tianbao.

Within one night, Longju Island turned into a white world. The long mountains resembled giant snakes with white backs, stretching toward the grayish waters. Dozens of soldiers carefully cleared the paths up the mountains, spreading coarse salt to melt the snow and then covering it with layers of dry grass.

On the mountain top, Yinglong City, which was already under construction, was also covered in snow. A dozen soldiers were busy clearing the snow to reveal large patches of green stone.

Yinglong City had been under construction for a month and was now as tall as two people. However, they had hit a bottleneck: a shortage of building materials. The granite on Longju Island was extremely hard to quarry, while although there were stones available in Shenwei City, the Tubo army was watching closely, making large-scale transportation impossible. Due to this shortage, construction had been intermittent, and it had been halted for five days since the third day of the tenth month.

More than a hundred tents at the foot of the mountain were also covered in snow. The number of soldiers stationed on Longju Island had risen to two thousand. Another thousand had not yet arrived because the castle was not yet complete. But at the far west end of the tents, there were two temporarily built stone houses. Several soldiers came and went from these houses, their serious expressions adding to their mystery.

Inside the stone houses, it was steamy. Ventilation openings had been made in the upper corners of the walls, allowing the north wind to blow in. Yet, the room was still filled with a pungent stench. In the center of the room stood a large pottery pot, with red-hot coals burning beneath it. Li Qing’an, the ruler of Longju Island, had now become a chemist. Wearing a wooden gas mask and with bloodshot eyes, he kept stirring the contents of the pot with a wooden stick while occasionally peeking in to check.

At the other end of the stone house, another large pottery pot stood, also with coals burning beneath it. Boiling water surged inside, bubbling with milky white bubbles. Several soldiers were busy around the pot. Like Li Qing’an, they wore wooden gas masks and endured the stench as they added gunpowder collected from bird droppings to wheat straw and plant ash in a ratio of eight to one. They then poured it into the boiling water to dissolve and boil it. After about fifteen minutes, one soldier shouted, “It’s ready!”

A few other soldiers immediately unrolled a piece of burlap and held its corners tightly. Beneath the burlap was a large wooden barrel. Three strong men wrapped the edges of an earthen pot with cloth, lifted the pot, and slowly poured the boiling white slurry into the burlap for filtration. The residue remained in the burlap, while the slurry filtered into the barrel.
“Done. Let’s do it again!”
The soldiers placed another earthen pot over the fire, poured the residue back into it, heated and stirred it for another fifteen minutes, then filtered it once more. Finally, they mixed the slurry from both filtrations and brought it to Li Qing’an.
“General! This barrel is ready.”
“Good. Mine is almost done too.”
Li Qing’an found it difficult to stir with the stick. The pot contained pure white slurry, with most of the water having evaporated, leaving a thick syrup-like liquid. At that point, he handed the stick to a soldier nearby and took a long-handled wooden spoon to scoop out a spoonful of colorless, viscous slurry and pour it into a bowl. As the temperature dropped, a gel-like substance quickly formed in the slurry.
“It’s ready. Filter it again!”
A few soldiers immediately came over, lifted the pot, let it cool slightly, and filtered it through white cloth again. Gel-like, colorless clumps remained in the cloth, while the saltwater was filtered out. After several more cycles of heating, dissolving, and filtering, and as the temperature dropped, a full barrel of purified white crystals was obtained.
Li Qing’an stood up, gently tapped his legs, which had gone numb from squatting, and his face lit up with joy. These were the potassium nitrate crystals he had produced using traditional methods—commonly known as “local nitrate.”
“General, will this work?” one soldier asked curiously.
Li Qing’an smiled, took a small piece of the solidified crystal, crushed it into powder, and threw it into the red-hot charcoal. Sparks flew everywhere, startling the soldiers who quickly stepped back.
Li Qing’an said proudly, “See? This is truly useful.”
The soldiers all sighed in relief—this stuff could actually explode.
“Alright! Carry it to the next room. Everyone, continue.”
The soldiers carried the purified local nitrate to another stone house, while Li Qing’an took a small barrel of the crystals back to his tent. To overcome the difficulties in quarrying, he thought of black powder. Black powder had been invented as early as the Eastern Jin Dynasty, but it had always been used in the production of elixirs; no one had considered its other uses.
But Li Qing’an knew well the properties of gunpowder. He had just never had the time to seriously consider it. This setback in quarrying reminded him that gunpowder might help him solve this problem.

Obtaining the formula for gunpowder wasn’t very difficult. When Li Qing’an was in Kucha, he had gotten it from a alchemist: 60% saltpeter, 25% sulfur, and 15% charcoal. Grinding them into powder and mixing them together created black gunpowder. Longju Island had bird droppings accumulated over hundreds of years, so there was an abundance of nitrate, and charcoal powder could also be obtained easily. The key now was sulfur, which was unavailable on Longju Island. Nevertheless, he managed to find two jin from an item carried by a soldier. How many stones could black gunpowder made from two jin of sulfur blow apart? This left Li Qing’an deeply worried. He sighed softly, set down the freshly mixed packets in his hands, and paced back and forth inside the tent. But with no sulfur, even the most skilled cook couldn’t prepare a meal without ingredients. Li Qing’an lifted the tent curtain, and immediately, bright white snowlight streamed in. The north wind was extremely cold, carrying snowflakes that fell heavily from the sky. From his vantage point, he could see the distant sea, which was vast and empty, with no ships in sight. Li Qing’an grew anxious. Half a month earlier, he had heard from the monk Fahai at the temple that there was an abundance of natural sulfur in the middle section of Datong Mountain, which was easy to mine. He had then ordered He Yanming to lead over a hundred people in two ships to search for the ore. Half a month had passed, yet there was still no news. Li Qing’an feared they might have encountered the Tubo army; if necessary, he would send someone to Shanzhou to purchase it. He returned to the tent and carefully poured the already mixed packets of black gunpowder into small pottery jars. This gunpowder was made from the only one jin of sulfur he had. Although he had obtained the formula from the alchemist, he didn’t know its explosive power. Therefore, he had prepared several types of gunpowder with gradually increasing saltpeter content and labeled the jars accordingly. At that moment, a bodyguard reported from outside, “General! The site is ready.” “I’m coming right away.” Li Qing’an picked up the small jars of prepared gunpowder and hurried out of the tent. The snow had stopped completely, turning the island into a white world, as if covered in a thick white coat. Li Qing’an, along with a few soldiers, rode horses toward the south side of the island. To the south of Longju Island were three large valleys. Two of them were used to store horses, while the smaller one was unused and perfect for testing gunpowder. When Li Qing’an arrived at the valley, several Tang soldiers were already there. The valley wasn’t large—twenty zhang long and five zhang wide—with dark granite on both sides. The snow inside had been cleared away. Despite how fiercely the north wind blew, it was very quiet inside the valley, with no trace of the cold wind, which was favorable for testing gunpowder.

A total of twenty soldiers, including Tang Jun, participated in the experiment with Li Qingan. They were all trusted men selected by Li Qingan from the Jiangdu Camp and the Hexi Army. This gunpowder experiment was of great significance, and Li Qingan classified it as top-secret military information; aside from a few officers, ordinary soldiers knew nothing about it.

The testing platform was located in a corner deep within a mountain hollow—a five-foot-square piece of bluestone. Li Qingan personally placed the pottery jar on the stone. The jar was about the size of a pomelo. He then used a long rope soaked in kerosene as a wick, stretching it out about thirty feet long before inserting the other end into the jar.

“General, shall we start?” asked a soldier in charge of lighting it in a low voice.

“Wait a moment!”

Li Qingan took a small wooden box and carefully covered the jar with it. After looking around, he nodded and said, “It’s fine. Let’s begin!”

Everyone quickly retreated ten feet away, eagerly waiting for the miracle Li Qingan had spoken of. Li Qingan felt somewhat uneasy. The gunpowder in the jar contained 60% nitrate. His intuition told him the results might not be very good. The soldier lit the oil rope, and it immediately caught fire. The flames spread rapidly, reaching the box in the blink of an eye. The soldier, terrified, tried to run but tripped and fell to the ground, holding his head tightly and not daring to move. This sudden accident made Li Qingan’s heart pound. At that moment, there was a muffled “bang!” The wooden box was lifted ten feet into the air, and black smoke billowed into the sky.

Everyone exclaimed in shock and rushed forward, discussing excitedly. It was their first time seeing gunpowder. Although it wasn’t as astonishing as Li Qingan had described, it still scared them.

Half of the jar had been shattered into pieces, while the other half remained intact. The bluestone surface was covered with unburned black gunpowder, clearly due to the gunpowder being compressed too tightly, preventing it from burning fully. Most of the shattered pieces were embedded in the inner walls of the wooden box, but a few fragments flew out. One of them hit the soldier who lit the fire, causing a bloody wound on his leg. The wooden box was also shaken loose but did not collapse.

“Qilang, is this gunpowder?” asked Li Fei Shouyu curiously.

“Yes! This is gunpowder. How does it feel?” Li Qingan asked back with a smile.

Li Fei Yuanli beside him curled his lips and said, “It doesn’t feel great. It might scare horses, but for me? Just my eyelid twitched.”

“I’ll do it again.”

Li Qingan took another jar of black gunpowder. The label indicated its composition: 70% nitrate, 20% sulfur, and 10% charcoal. He couldn’t remember the exact composition of gunpowder in later times, but he vaguely recalled that nitrate made up 70%.

“Come! Try this jar again.”
Last time, the gunpowder was packed too tightly. This time, he poured out some of it and loosened the clay jar before placing it on the bluestone and covering it with a wooden box. This time, Li Qing’an didn’t use a human to light it but instead a rocket. Standing fifteen zhang away, they slowly drew their bows. A ball of fire burned fiercely at the tip of the arrow. When the string was released, the rocket shot high into the air, tracing a parabolic path before precisely hitting the oil rope. The oil rope caught fire and quickly spread to the wooden box, like a fire serpent, vanishing into it with a “whoosh!” Before anyone could react, a deafening explosion rang out as the gunpowder detonated violently. Black smoke billowed into the sky, and the wooden box was shattered into pieces, flying high into the air.
Li Qing’an slowly knelt down, his eyes filled with excitement. Suddenly, he slammed his fist into the ground. Seventy percent nitrate! Seventy percent nitrate was the proper ratio for gunpowder. It took the people around him a while to recover from their shock. Li Feiyuanli widened his eyes and muttered to himself, “My goodness, this is like the Thunder God in action!”
“Qilang, let’s do this!”
Even the usually calm Li Feishouyu couldn’t contain his excitement. He punched his fists together and said solemnly, “With such a thunderous weapon, why worry about the Tubo army not being defeated? It’s time for our Anxi army to show its valor.”
Li Qing’an nodded and smiled at everyone. “This gunpowder still needs further refinement before it can be used as a weapon. But for now, I’m only focused on figuring out how to blow up the rocks.”
Just then, intense horseback sounds came from outside the valley, along with faint shouts: “General! General!”
Li Qing’an quickly stepped out of the valley and saw a soldier on horseback, struggling to control his horse.
“What’s the matter?”
“General, Captain He has returned!”
……
He Yanming didn’t disappoint him. Guided by a local Qiang man, they found a high-quality natural sulfur mine in the middle section of Datong Mountain, securing thousands of pounds of natural sulfur.
When Li Qing’an arrived by the sea, the soldiers were loading baskets of sulfur onto the shore from the ship. Seeing Li Qing’an, He Yanming hurried over, knelt down, and saluted militarily. “I’ve fulfilled my mission successfully and found the sulfur mine.”
“Did you encounter any Tubo soldiers?”
“No. With the local Qiang man as a guide, we avoided their patrols.”
“Well done. I’ll remember your great contribution this time.”
He Yanming was overjoyed. He quickly brought over a basket of sulfur and said with a smile, “The Qiang people said there’s even more sulfur in the Qilian Mountains. If the general needs more, I can go back and bring back tens of thousands of pounds.”

Li Qing’an gazed at those long-awaited reddish-yellow sulfur crystals, his heart bursting with joy. With them, his black gunpowder could finally be created. He nodded and turned to the others with a smile, saying, “With these several thousand pounds of sulfur, our Yinglong City will be repaired soon.”

…

With sulfur in hand, Li Qing’an successfully created his black gunpowder. Yet, figuring out how to turn it into a powerful explosive took some thought from him. Unlike regular explosives, black gunpowder didn’t yield great power in small amounts—it required large doses. After much consideration, Li Qing’an decided to create a simple yet effective device. As a child, he had been injured by a firecracker, an experience that left a deep impression on him.

Firecrackers were made by tightly wrapping gunpowder in layers of paper to form a cylinder, which was then covered with iron sheeting. When exploded, the resulting shockwave was strong enough to shatter hard granite.

In just half a day, Li Qing’an produced three large firecrackers, each as tall as a person and two feet in diameter—resembling the large plastic firecrackers hung at store entrances during festivals, but these were genuine and functional.

This time, Li Qing’an didn’t act in secret. Under the watchful eyes of hundreds of Tang soldiers, three soldiers used ropes to lift a nearly hundred-pound firecracker and carefully placed it in a large rock fissure halfway up the mountain. The rocks in this area were broken, making them easier to quarry.

After placing the firecracker, the soldiers pulled its five-zhang-long fuse, thick as a finger, out of the fissure and secured the ignition end to a wooden board. Everything was ready. All the soldiers retreated 400 steps away and, as ordered by Li Qing’an, covered their ears with their fingers. The rest was left to Li Qing’an.

Standing 100 steps away on horseback, Li Qing’an slowly drew back his bow. A flame danced before his eyes. He took a deep breath, released the string, and the rocket shot out in a parabolic trajectory, flying toward the fuse with an ember attached.

“Click!” The rocket landed precisely on the wooden board, and the flame ignited the fuse attached to it. Li Qing’an turned his horse around and galloped away. After running just over 200 steps, he heard a thunderous explosion that seemed to shake the entire island. His warhorse, frightened, let out a loud neigh, lifted its front legs, and knocked him off his horse.

Li Qing’an held his head as dense showers of small stones flew at him, hitting his body with a crackling sound. Slowly, he turned his head to look behind and saw a plume of black smoke rising into the sky, forming a mushroom cloud. The immense force caused the cliff to crumble, with large rocks collapsing. As for the soldiers, most of them were like statues—standing or kneeling, their mouths wide open, eyes filled with terror.

With the help of gunpowder, building materials for the city kept arriving in abundance, and the soldiers’ morale was high as they worked together to construct the city. In just twenty days, the outline of Yinglong City, three zhang high, took shape.

That afternoon, as usual, Li Qing’an inspected the progress of the construction inside Yinglong City. Covering over twenty mu, the city was large and sturdy, capable of housing two thousand soldiers.

More than a thousand soldiers were busy inside the city. They mixed lime with water to make mortar and laid smooth granite blocks together without any gaps. Once the mortar dried, the city walls became extremely strong. The entire wall was about one and a half zhang wide, with the middle part compacted with yellow soil.

Li Qing’an walked up to several soldiers and asked with a smile, “How much longer will it take to complete the city?”

The soldiers quickly saluted. The leader among them was Luo Han, the Han slave leader rescued in Haixi. His injuries had fully healed, and he had rejoined the Tang army. With extensive experience in building cities, he was now the chief commander of Yinglong City’s construction.

He bowed and said, “General, in another half month, the main structure of Yinglong City will be completed. The rest are just some finishing touches—perhaps another month at most.”

Li Qing’an nodded. “Speed is important, but more crucial is ensuring the city is sturdy enough to withstand storms.”

“General, rest assured, there won’t be any problems!”

Just then, someone suddenly shouted, “General, look! A beacon fire!”

Li Qing’an rushed to the city wall and saw a thin wisp of black smoke rising at the end of the vast sea. It was from the beacon towers on three reefs thirty li to the south. Li Qing’an’s heart tightened instantly.

The Tibetans were coming!