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

Before the Yan-character flags on the walls of Zhen Ding had been flying for three days, Zhu Di's central army had already broken camp and marched south.

In Hebei, April is a time of fluctuating temperatures, with the wheat fields along the official roads just beginning to turn green, and horses' hooves could leave small puddles of overnight rainwater. The Yan army, starting from Zhengding, advanced southeast along the south bank of the Hutuo River. Their vanguard cavalry covered 120 li in a day and night, capturing the county towns of Shulu and Hengshui in succession. The defending southern magistrates offered virtually no resistance—Sheng Yong had just suffered a defeat at Jiahe, and with the fall of Zhengding, the imperial prefectures and counties in the heart of Hebei had lost their central command. In many places, even when the Yan army was still 30 li away, the defenders had already sealed the treasuries, placed the city gate keys at the government offices, and fled south with their families overnight.

Zhu Di did not linger in these counties. His objective was clear: to eliminate all the court's strongholds on the Hebei Plain before Sheng Yong and Tie Xuan could reunite. Zhang Yu and Tan Yuan were dead, but the deaths of these veteran generals did not halt the Yan army's offensive—on the contrary, they allowed Zhu Di to maximize the speed advantage of his cavalry. He divided his army into three routes: Zhu Neng led the main force of infantry and cavalry to advance along the official road; Chen Mao led light cavalry to flank from the west; and Shen Du's centurion's garrison and Huo Zhen's elite cavalry of the Doyan Three Guards served as the vanguard of the eastern route, advancing south along the east bank of the Grand Canal, with their target being Nanpi, south of Cangzhou.

Nanpi served as a transit point on the grain route between Dezhou and Jinan. After Sheng Yong retreated from Jiahe to Dezhou, Nanpi became one of his few outer granaries. The city held over 30,000 shi (a unit of dry measure) of military rations transported from Jinan. The defending general was Zhuang De, one of Sheng Yong's subordinates, with 4,000 infantry and 300 musketeers. He had dug two trenches and laid three layers of deer antlers outside the city. Zhuang De was a renowned defensive general under Sheng Yong—he didn't attack, didn't launch surprise attacks, and didn't employ any fancy tactics; he simply deepened the trenches, reinforced the deer antlers, and polished his muskets, then waited for the siege. This tactic was most effective against cavalry charges: if the enemy wouldn't come out to fight, you could only pour your own lives into the city.

When Shen Du set up camp at the canal ferry thirty miles outside Nanpi City, the scout sent out by Huo Zhen had already returned. The scout was the youngest rider in the Doyan Three Guards, not yet twenty years old, with the Mongolian name Narisong. He spoke broken Chinese, but his drawing skills were extremely accurate. He squatted in front of Shen Du and used his dagger to draw the outline of Nanpi City on the muddy ground, and drew two circles outside the city.

"The first one is a deep moat with water. The second one is behind the moat, with three layers of antlers. On the city wall, over here—" He pointed to the east side of the city wall, "lots of muskets. Over here—" He then pointed to the west side, "fewer people."

Shen Du stared at the two circles for a long time. Zhuang De's formation was exactly the same as Sheng Yong's at Jiahe—a thick front, thin flanks, muskets to reinforce the position, and a defensive stance. If he launched a frontal assault, he would be chipped away at the infantry at the forefront by the muskets, just like on the first day at Jiahe. Although his recruits had trained all winter, they had never fought a real siege. Charging into this formation right away would result in heavy casualties.

"There are few people." Shen Du pointed his dagger at the spot on the muddy ground that represented the west side of the city wall. "Why are there so few people?"

Na Risong drew a wavy line on the outside of the west side of the city wall with his finger. "A river. A small river. There's no bridge. The attackers can't cross. So they don't let many people pass."

Shen Du stood up and patted the mud off his knees. He turned to Zhao Laoliu and said, "Go check out that little river to the west. Take a shovel, find out the water depth and the hardness of the riverbed, and report back before dark."

When Zhao Laoliu led the two veterans from the obstacle-breaking team to the small river on the west side of Nanpi, the sun was already setting. The river was indeed small, no more than seven or eight zhang wide, and its banks were covered with reeds that had withered all winter and had not yet turned green. But the river was shallower than he had expected—the spring floods had not yet arrived, and most of the riverbed was exposed, with only a shallow line of water in the middle, less than two feet deep at its deepest point, which could be waded across by rolling up one's trousers. More importantly, there was the riverbed—he dug down a foot with a shovel, and it wasn't silt, but sand and gravel. The sandy and gravelly riverbed didn't sink underfoot, and the iron-rimmed wheels of the battering ram could run over it.

"It's tough enough." Old Zhao planted his shovel in the ground. "Uncle Li, it can get through the battering ram."

That night, Shen Du spread out a rough map of Nanpi's defenses in his tent at the canal ferry crossing, and summoned Gu Zhang, Zhao Laoliu, and Huo Zhen together. Under the oil lamp, his face was clearly lit by the firelight, and the old wound in his left leg ached again from the long march, but he did not sit down. He stood with his sword in hand, and used his dagger to draw an attack route on the map.

"Zhuang De's formation is too thick. The main city gate is to the north, with two moats and three barricades, and all the muskets are pointed to the north. To the east, there is a network of canals that prevents the deployment of large forces. To the south is the narrowest point between the city wall and the barbican, so even if the south gate is captured, the troops cannot be deployed. Zhuang De didn't pay much attention to the small river to the west. He thought the river could block siege equipment, but Zhao Laoliu scouted it out—the riverbed is sand and gravel, and the water is less than two feet deep. Battering rams can run right over it. While Zhuang De concentrated his forces to the north, we circled around to his rear from the west."

Gu Zhang pressed his finger on the spot on the sketch that represented the west side of the city wall: "A direct attack from the west?"

"Don't attack the city wall yet." Shen Du drew a small circle on the west side of the city wall with his dagger. "Huo Zhen, take the mounted archers and sneak across the small river to the west before dawn. After crossing the river, don't rush towards the city wall. Go south and circle around to the official road south of Nanpi City that leads to Dezhou. Once Zhuang De realizes the city has fallen, he will definitely send someone to break through the south gate to send a message to Dezhou. Intercept all his messengers. Don't let a single one escape."

Huo Zhen pulled the dagger from the horse bone and carved a mark on the official road: "None of them will escape."

"After Gu Zhang leads the swordsmen, shieldmen, and spearmen across the small river to the west, they will ambush outside the city. Once Zhao Laoliu blows open the west gate, you will push inwards, targeting the granary in the city center. Forget about the government offices and military camps; seize the granary first—Zhuang De's military rations are all piled up there. Once the granary is captured, the garrison won't be able to hold out for long. Zhao Laoliu will lead the breaching team to push the battering ram across the river. You don't need too much gunpowder; the west gate isn't the main city gate, and the iron hinges are half the thickness of the gate tower. Two bundles of gunpowder will be enough to blow it open." He sheathed his dagger, his voice very soft. "There's one more thing—Zhuang De himself cannot die. He is Sheng Yong's subordinate. If he surrenders, the other garrison commanders under Sheng Yong will know that the Yan army doesn't kill surrendered prisoners."

The attack began in the darkest hour before dawn. Huo Zhen's three hundred elite cavalrymen crossed the western river with their horses' hooves wrapped in hemp cloth, and the sentries on the opposite bank didn't notice until the first rank of mounted archers was less than two hundred paces from the city wall. The alarm gong had barely sounded when the archers' arrows rained down on the western wall. Zhuang De's garrison on the western wall was indeed small—less than two hundred infantrymen and a few dozen archers—who were forced to cower behind the battlements by the volley of arrows, too afraid to raise their heads.

Zhao Laoliu pushed the battering ram across the stream. The pebbles on the riverbed crunched under the broad-bladed iron wheels, and the torchlight cast a dark red glow on the water. He had his pipe in his mouth, the embers flickering in the night wind. He pushed the ram to the west gate, the iron hinges gleaming dimly in the torchlight. He stuffed two bundles of new-style gunpowder canisters into the gap between the hinges and the rammed earth wall, extending the fuse to twelve feet—he'd used a two-foot fuse when bombing Baojiaying in Dezhou, and almost couldn't escape afterward; this time he'd learned his lesson.

"ignition!"

The fuse hissed as it drilled into the crack in the wall. A few breaths later, a muffled thud rang out, and the hinges of the west gate snapped, causing the entire gate to tilt outwards. Before the door had even fully hit the ground, Gu Zhang had already led his swordsmen and shield-bearers through the opening. His left arm bandage had been torn open by splinters of wood from the door frame during the charge, reopening an old scar, but he felt no pain. His sword felled the first Southern Army centurion charging up from the inside of the opening, his shield slammed into the second spearman, and the spearmen behind him filed in, their spear tips gleaming coldly in the firelight. They advanced along the base of the city wall to the north and south, firmly wedging their well-practiced rampage formation onto the west gate tower.

When the explosion at the west gate reached the city center, Zhuang De was on the north gate tower. He froze for a moment when he heard the sound—it wasn't the north gate, it was the west gate. From the direction of the small river. He had deployed all his main forces to the north, leaving only two hundred men at the west gate. He immediately sent a messenger to the south gate, ordering the reserves to block the west gate, but the messenger was intercepted by Huo Zhen's mounted archers less than an incense stick's time after riding out of the south gate. A second group of messengers took a side path to the east, but were similarly intercepted by the Duoyan Three Guards who had been positioned along the canal. Zhuang De stood on the city tower for half an hour, but instead of reinforcements, he heard increasingly loud shouts of battle from the west gate and saw flames rising from the direction of the granary.

"The granary is on fire!" the sentry on the city wall shouted hoarsely.

When Zhuang De saw the flames rising from the direction of the granary in the city center, his lips tightened into a thin line. The granary contained over 30,000 shi of military rations, the entirety of his supplies allocated to him by Sheng Yong from Jinan. If the granary fell, even if he repelled the Yan army, the garrison wouldn't last more than three days. He slowly removed his helmet and held it in his hand, turning to his adjutant behind him and saying, "Pass down the order—open the north gate."

Nanpi surrendered. Zhuang De, holding his sword, walked out of the north gate and knelt on one knee before Zhu Di's horse. His face was ashen, but his back was ramrod straight. "This guilty general, Zhuang De, is willing to lead his troops to surrender."

Zhu Di sat on his horse, looking down at the garrison commander. He didn't humiliate him, nor did he say anything superfluous; he simply nodded: "You are a good commander. Rise." Then he dismounted and said to the messenger behind him, "Issue the order to the entire army—Nanpi has surrendered. All Southern soldiers within the city must be treated with courtesy. No killing of surrendered soldiers is permitted, and no looting is allowed. Anyone who disobeys will be executed."

Shen Du stood beside the ruins of the West Gate, watching Zhuang De being helped up by Zhu Di. Behind him, Zhao Laoliu squatted on the shattered remains of a gate, half a dry biscuit dangling from his mouth as he chewed and observed the still-smoking city tower. Gu Zhang sat at the foot of the city wall, having the military doctor re-stitch his left arm wound. His lips were white with pain, but he didn't utter a sound.

After the capture of Nanpi, Dezhou was the last obstacle for the Yan army on the Hebei Plain. Sheng Yong had just suffered a defeat at Jiahe, Zhuang De had surrendered, and Wu Jie was still gathering his remaining troops after his defeat at Zhending. Shen Du leaned against the rammed earth wall of the West Gate, closing his eyes for a moment. The rubble on the inner side of the city wall was digging into his injured left leg, but he didn't move. The shouts of battle had stopped, the fire in the granary had been extinguished, and the sounds of commands to gather surrendered soldiers and the clanging of metal came from the center of the city—Yan soldiers were piling up the weapons surrendered by the surrendered soldiers. The footsteps were mixed with Zhao Laoliu's hoarse shouts; he was leading the breaching team to drag the battering ram down from the ruins of the West Gate, cursing as he dragged it, saying that the axle had crushed the shards of the door. Shen Du didn't open his eyes again, wanting only to rest against the wall for a little while.