In this realistic war game, only I understand the course of the battle.

When Murong Chui's envoy arrived for the third time, his attitude was much more respectful than the previous two times. This wasn't feigned respect, but genuine politeness. During his stay at the inn, the porridge he drank each day was indeed thicker than in the first two days. The armor of the city's garrison, though worn, was polished to a gleaming shine, and the patrols on the city walls moved with orderly and rhythmic steps. He returned and reported the situation truthfully. Murong Chui listened in silence for a long time, then ordered the camp, which had been advancing towards the city walls, to be withdrawn several miles. This withdrawal wasn't merely a change in distance, but a change in mindset—Murong Chui began to reassess the city's strength.

That morning, Shen Du sat by the crenellations of the city wall, a small piece of charcoal in his hand, sketching on a white silk sheet spread out before him. For the first time since the siege was lifted, he wasn't drawing defensive fortifications, marking crossbow firing angles, or calculating the area to be splashed with kerosene. He was drawing the layout of Chang'an's streets and alleys—the open spaces inside the city walls, abandoned market towns, the ruins of burned-down granaries, and the shacks surrounding the drill ground. He circled each open space with charcoal, and next to it were detailed plans: the low-lying land beside the canal in the west of the city could be transformed into fishponds, using the Wei River to raise fish, and ducks could be raised on the surface; the sunny slopes at the foot of the city walls could be terraced to grow short-cycle vegetables; the abandoned stables next to the drill ground could be converted into chicken coops, and the fermented horse manure could be used as fertilizer.

Old Wei squatted down beside him, watching for a long time, before finally asking, "Uncle Shen, what are you drawing? A chicken coop? Aren't we supposed to be defending the city? Why are you drawing a chicken coop?"

"Defending a city can't rely solely on its walls." Shen Du didn't look up, his charcoal pencil continuing to trace across the white silk. "Walls can hold off enemies, but they can't stop hunger. The supply lines outside the city haven't fully recovered yet. Although the Xianbei have retreated, they could turn on us at any moment, and Yao Chang is still eyeing us from the north of the Wei River. If we can't establish a stable food source within the city, we'll still starve to death when they besiege us again. That low-lying area to the west of the city is right next to an abandoned irrigation canal; we can draw water from the Wei River to raise fish there. We can cultivate vegetables on the sunny slopes at the base of the city walls, using wood ash as fertilizer, and we can harvest a crop every month."

As he spoke, he sketched a second draft on another piece of white silk with a charcoal pencil—a simple wooden frame with a crossbeam supporting it, and a broken iron pot hanging below. This was a simple water purification device he had seen when studying ancient logistics history at military school, a common method used by Han Dynasty armies in water-scarce areas: wastewater was poured into the iron pot and boiled; the steam rose to the cold iron plate above, condensed into water droplets, and slid down the sloping plate into a nearby earthenware jar, leaving mud and impurities at the bottom. The resulting water was drinkable. "Over there in the wounded soldiers' camp, many wounded soldiers' wounds festered not because the cuts were too deep, but because the water used to wash the wounds was unclean. The same goes for the drinking water—more soldiers had diarrhea than those with arrow wounds. Zhou Jing said that if there wasn't clean water, half the people in the wounded soldiers' camp wouldn't survive the winter. After this system was set up, using scrap wood collected from the ruins as firewood, they could steam several vats of clean water a day, enough for the wounded soldiers' camp."

Old Wei took the sketch and examined it several times, his eyes growing brighter with each look. He tucked the sketch into his coat, stood up, and dusted off his knees. "Alright, I'll take some men to dig a pond over the irrigation ditch right away. The chicken coop is easy too—I've been wanting to tear down that dilapidated stable by the drill ground for a while now; those rotten logs are perfect for building a chicken coop. You wait, I'll have it ready for you before dark tomorrow."

"Where do chicks come from?"

"Don't worry about this," Old Wei waved his hand. "I used to raise chickens back in my hometown of Huaibei. There must be some chickens that the defeated soldiers brought with them in those shack areas near the city wall. I'll go and trade with them—in exchange for my own food rations."

Shen Du stood up and watched Lao Wei's figure disappear around the corner of the city wall. Then he put away his charcoal pencil, rolled up his drawings, and headed towards the wounded soldiers' camp. Just as he reached the camp gate, Zhou Jing came out, carrying a broken earthenware basin half-filled with muddy water. Seeing Shen Du, he placed the basin on the ground and pointed to the contents: "Look at this water—it's freshly drawn from the Wei River, and it's 30% mud and sand. Half the wounded soldiers who drank this water got diarrhea. I used to filter it with cloth, but I didn't have enough cloth, and it didn't filter out the fine sand." He led Shen Du to his makeshift water purifier, looked at the drawings Shen Du had given him, and then at the broken iron pot. Suddenly, he laughed: "I've seen this method before—when I was serving in the army in Liangzhou, an old military doctor used something similar, but not to steam water, but to steam herbs. Using this for water purification will be much more effective than my cloth filter. I'll have the wounded soldiers build their own purifier immediately."

They squatted in the courtyard of the wounded soldiers' camp for an entire afternoon, repeatedly experimenting with scraps of wood and broken iron pots salvaged from the ruins. They adjusted the angle of the iron plate, the heat below, and the rhythm of adding and removing water, finally steaming out the first batch of clean water. Zhou Jing dipped his finger in the water, tasted it, nodded, and then had someone take the water to the wounded soldiers with the most severe diarrhea.

After leaving the wounded soldiers' camp, Shen Du passed by the ruins of the granary. The burned-out outer walls of the granary still lay on the ground, charred beams lay across the rubble, and a faint smell of burning lingered in the air. Azhi sat on a broken brick outside the ruins, a tattered account book spread out on her lap. She was writing something neatly in the book, holding a small piece of charcoal pencil in her hand, her writing extremely careful, each stroke precise and clear. After the granary burned down, she built a small shed next to the ruins and carefully reorganized the account books, storage slips, and grain allocation records she had salvaged from the fire, pasting them onto clean white silk, each page marked with the date and the person in charge. She changed the original granary's entry and exit procedures to a simpler method—each bag of grain was numbered when it entered the warehouse, and crossed out in the account book when it left, so that even if the account book was burned, the numbers on the bags could still be used for verification.

"Master Shen." Ah Zhi looked up and saw him, put down her charcoal pencil, stood up, and took out an old, faded blanket from the shed. "This is for you. Yesterday I went to the west of the city to help distribute grain, and I saw a laborer uncle who brought you a portion as well. He said your legs hurt at night, so you should put this blanket under your knees."

Shen Du took the blanket. It was so thin it was almost translucent, but it was very clean and neatly folded. He draped the blanket over his arm and looked down to flip through Azhi's account book. Every entry and exit was recorded in the correct place, and the cover had the two characters "Amu" written crookedly. These two characters were now being imitated more and more like her brother's handwriting.

"Several bags of millet were transferred from the western grain depot to the garrison today. The Xianbei envoy brought a cartload of medicinal herbs in the supplies yesterday, which Uncle Zhou has already taken. Also, Uncle Wei said he'll take some people to till the land by the western irrigation canal this afternoon, and he'd like to ask if you want to plant radishes." After she finished speaking, she lowered her head and added a note to the ledger, then looked up at Shen Du, her eyes holding the same light as when Amu asked on the Xiaoshan plank road, "Is Guanzhong beyond this mountain?" Shen Du draped the blanket over his shoulder and said that radishes were fine, and that he should have Uncle Wei till the land first, and the seeds would be distributed when the next supply arrived.

Emerging from the granary ruins, Shen Du went to the abandoned irrigation ditch west of the city. Old Wei, shirtless, stood in waist-deep mud, wielding a broken shovel to dig through the ditch. He had given his rations to the newly recruited defeated soldiers, drinking only two bowls of thin porridge a day, but his strength in swinging the shovel hadn't diminished at all. During the siege, they only slept two hours a day, and now he still got up before dawn to work. He said that staying still would lead to idle thoughts, while working gave him peace of mind. A small patch of land beside the ditch had already been turned over, and several defeated soldiers were squatting on the ground, crushing the clods of earth with their hands, picking out the pebbles and tiles, and then digging neat furrows with wooden sticks. Shen Du walked over, squatted down, and examined the soil. It was alkaline, but mixing it with wood ash and well-rotted manure would improve it. He had someone cut up the old bandages and tattered blankets discarded from the wounded soldiers' camp and mix them into the soil to ferment, saying it would fertilize the soil. A young deserter asked why rags could fertilize fields. Shen Du squatted down and dug through a layer of soil to explain to him, "Raw cloth is plant fiber. After it rots, it decomposes into nitrogen, which is fertilizer. It's the same principle as when you use wood ash to fertilize fields in the countryside." The young deserter nodded as if he understood, and the veterans nearby also came over to look.

A few days later, in the afternoon, the open space marked on the map by Shen Du, located beneath the east city wall, suddenly became bustling. He instructed Lao Wei to level the space and pave a simple path with rubble and broken bricks salvaged from the ruins. He then erected several rows of sunshades on either side of the path using wooden stakes and old cloth. Nearly thirty percent of the people in Chang'an had died during the siege, but the survivors still needed to trade. Markets were beginning to sprout anew amidst the ruins. Farmers in the west of the city pushed wheelbarrows loaded with the first harvest of radishes and cabbages from the fields; hunters in the north carried rabbits and pheasants hunted from Mount Li on mules; women in the south sewed insoles and knee pads from rags and laid them out by the roadside to exchange for food. Several defeated soldiers, having salvaged scrap iron from the ruins of the Qiang camp, melted it down and forged it into hoes and sickles, tying them to wooden handles with hemp rope and placing them under awnings for people to trade.

Shen Du summoned Commandant Zhu and instructed him to set up a fair scale at the market entrance—made from old iron chains and scrap iron weights salvaged from the city wall. He said that all grain traded here must be weighed on the fair scale, and no shortchanging was allowed. Anyone who forced a sale would be dealt with according to the city's military law. Commandant Zhu nailed a wooden sign that read "Fair Trade" to a pillar of the stall and personally stood guard beside the fair scale.

Afterwards, when Shen Du went to the temporary palace to routinely report on the city's defenses, he returned the Crown Prince's guard token to Fu Jian and presented a detailed report—regarding the restoration of non-staple food production within the city, the construction of the water purification system, the management of the open markets, the number of wounded soldiers returning to their posts, the conservation of stored grain, and the remaining difficulties. Fu Jian sat behind his desk, read the report from beginning to end, and remained silent for a moment. Then he suddenly spoke, saying something that surprised Shen Du: "What you're doing in Chang'an, I did in Ye when I was young. Back then, I had just ascended the throne, and the world was in chaos. I personally cleared several acres of wasteland outside Ye to plant millet. Later, after I unified the north, I never touched a hoe again. What you're saying, I don't think is insignificant—it's better than those generals who abandoned their cities and fled." He folded the report and placed it on the corner of the table, then looked up at Shen Du. "People outside the city think that Chang'an has been besieged for nearly two months, and that the bones inside have long been broken. But I see that the bones are still there." Shen Du stood in the hall, bowing respectfully. Then he turned and walked out of the hall, standing on the stone steps looking at the myriad lights of Chang'an. Those lights lit up one by one in the winter night, sparse but still shining.