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

The locust trees at the Prince of Yan's residence had turned green again. A full year had passed since Shen Du returned from Qimei Mountain. Standing on the drill ground west of the Prince of Yan's residence, he watched the three thousand newly recruited infantrymen drill in formation. Half of these recruits were sons of military households drawn from various garrisons in Hebei, while the other half were young Mongolian horsemen who had volunteered from the grasslands of the Doyan Three Guards. They wore newly made cotton armor and carried long spears with extended shafts. On the drill ground, they changed formations at the command, their footsteps so synchronized that they sounded like a single person.

A year earlier, when the Yan army withdrew from Qimei Mountain to Beiping, it was almost decimated. Of the 60,000 elite troops who marched south, less than 30,000 returned capable of fighting. Their food supplies were exhausted, their gunpowder was depleted, and plague had claimed nearly 10% of their soldiers. But Zhu Di did not collapse. He converted all the iron smelters in Beiping into armories, organized the laborers into reserves, expanded the cavalry of the Doyan Three Guards from 3,000 to 8,000, and dismantled and studied all the muskets captured from Jiahe, Gaocheng, and Dezhou, replicating them to create a batch of new bronze muskets. More importantly, he did something he had never done before since the beginning of his rebellion—he promoted Li Jingzhong from a centurion to a commander-in-chief, appointing him as the commander-in-chief of the city-breaking camp with the rank of deputy commander of the guard, while also concurrently leading the newly formed mixed infantry and cavalry vanguard camp. Not a chiliarch, but a direct promotion from centurion to deputy commander of the guard. This appointment caused quite a stir within the Yan Army—a young man in his early twenties rising from infantryman to deputy commander in less than four years, skipping four ranks from general to centurion, deputy commander, and commander, was unimaginable in the Hongwu era. But no one dared to question it openly. From Baigou River to Qimei Mountain, every battle Li Jingzhong fought was recorded in the military merit book; the city gates he blew up and the defenses he breached were more convincing than any seniority.

Beside the drill ground, Zhao Laoliu squatted beside the wheel of a new-style battering ram, a pipe dangling from his mouth, tightening the iron clamp on the axle with a wrench. The graze on his left arm from the anesthetic crossbow bolt had long since healed, but his left hand was still not as dexterous as before; when tightening the wrench, his right hand exerted force while his left hand could only support him. He finished the last turn, put the wrench on the ground, stood up, dusted off the rust on his hands, and looked at the densely packed formation of new recruits on the drill ground. "Three thousand men," he said, pulling the pipe from his mouth and turning to Shen Du standing behind him. "Master Li, a year ago when we set off from Dezhou, the entire centurion's garrison had less than eighty men."

"Not enough." Shen Du stood on a high platform beside the drill ground, holding a newly completed map of the Yangtze River crossing operation. His old injury in his left leg still ached slightly on rainy days, but his posture no longer showed any limp. He unfolded the map, which depicted the hydrology of the lower Yangtze River, from Caishiji upstream of Nanjing to Zhenjiang downstream. The depth, current speed, width of the river, and terrain on the opposite bank of each crossing were clearly marked in fine pen. "Last year's southward advance failed. The biggest problem wasn't Qimei Mountain—Qimeishan was just the final result. The real problem was crossing the rivers—the Huai River and the Yangtze River. For each major river, we had to find boats and build pontoon bridges on the spot. This method works for smaller rivers, but not for the Yangtze River. The Yangtze is three times wider than the Huai River, the current is much faster, and there's a navy on the south bank."

He turned to the next page of the map, which depicted a newly designed ferry—a flat-bottomed, double-decker vessel with a removable iron baffle at the bow and a shipboard crossbow modified from captured Southern army crossbows at the stern. "We've accomplished three things this year. First, our gunpowder and muskets have doubled compared to last year. Second, our mixed infantry and cavalry formations are now well-established; the mounted archers of the Doyan Three Guards and the infantry of the City-Breaking Battalion can coordinate their attacks within thirty breaths. Third, there are the boats. We need to cross not only the Huai River but also the Yangtze. His Highness has ordered the secret construction of ferries in Beiping, disassembling them into parts and transporting them to the Huai River for reassembly. This southward journey will not repeat the predicament of the last—there will be no more times of having no boats available and being left to sigh at the river."

In February, spring arrived and the Grand Canal thawed. The Yan army marched south again. This time, Zhu Di did not take a detour, nor did he attack Cangzhou, Dezhou, or Jinan. He divided his 100,000-strong army into three routes. He personally led the central army south along the Grand Canal, Zhu Neng led the left wing to sweep through the southern army strongholds west of the canal, and Chen Mao led the right wing to cover the supply lines. The biggest difference from a year ago was the establishment of a faster communication system between the troops. The distance between the three armies was always kept within half a day's journey, allowing them to support each other at any time while still having enough space to deploy their respective marching formations. The southern army garrison commanders along the way discovered that this time the Yan army was no longer moving lightly and recklessly as before—they were not moving fast, but extremely steadily. Every section of the marching route had been surveyed in advance, every crossing had been bridged in advance, and every mountain pass where there might be an ambush had been searched in advance. From Beiping to the Huai River, no county dared to take the initiative to intercept them.

The Huai River ferry crossing. Shen Du stood at the same ferry crossing as last year, the surging Huai River before him. On the opposite bank, Mei Yin's Southern Navy had redeployed its defenses, with more ferries and warships than last year, and the shore fortifications were higher. Shen Du lowered his binoculars, a slight twitch at the corner of his mouth. A year ago, he had towed a boat from Weishan Lake to cross the river here, only to be cut off from supplies by Mei Yin's scorched-earth policy and suffer greatly at Qimei Mountain. This year, no one would tow boats from Weishan Lake anymore. The boats were behind him—not cargo boats, not fishing boats, but hundreds of flat-bottomed ferries secretly built in Beiping last year, disassembled into parts, transported to the Huai River by mules and horses, and reassembled in three days. Each boat could carry fifty people, and the bow was fitted with a detachable iron baffle capable of withstanding three volleys of crossbow bolts from the opposite bank.

More importantly, there was the gunpowder. Shen Du walked to the makeshift gunpowder shed beside the ferry, where Zhao Laoliu was leading his engineers to load bundles of new-style gunpowder canisters onto the ferry. These canisters were larger than those used last year when they blew up the west gate of Baojia Camp. Each earthenware canister was wrapped in a layer of hemp cloth soaked in tung oil, and the fuses were extended to fifteen feet. After Zhao Laoliu finished stacking the last bundle of gunpowder canisters, he patted the tung oil cloth off the canisters and said to Shen Du, "This is enough to blow up the shore defenses on the other side twice." Shen Du nodded and turned to Gu Zhang, who was standing to the side, "When we cross the river, you will lead the swordsmen and shieldmen in the first wave to set up a shield formation on the beach on the other side. Cover Zhao Laoliu as he pushes the gunpowder under the shore defenses. Huo Zhen's mounted archers will cross the river in the second wave. The crossbows will be set up at the bow of the boat to suppress the enemy first, and after the mounted archers land, they will spread out to the flanks. I will follow with the main force of the central army."

The crossing began at dawn.

The Yan army's cannons fired first. All the cannons captured from the Southern army at Jiahe and Gaocheng, along with newly cast bronze cannons from Beiping, were pushed onto the north bank of the Huai River. The gunners, shirtless, loaded powder and shells in the morning mist. This time, Zhu Di left no room for retreat—he concentrated all the cannons and bombarded Mei Yin's coastal defenses on the opposite bank for an entire day. Stones and gunpowder shells, trailing plumes of smoke, pounded against the earthen walls of the south bank, sending rubble and fragments of wooden fences flying into the air. Mei Yin's musketeers, crouching behind their fortifications, were pinned down by the barrage, while the crossbowmen were buried beneath the collapsed earthen walls.

Before the cannon fire had even ceased, the first batch of ferries to Shendu had already been launched. Zhao Laoliu squatted at the bow of the first ferry, one hand gripping the hemp rope on the deck, the other stuffing his pipe into his mouth and biting it tightly. The ship's crossbows fired continuously from both sides of the bow, the bolts embedding themselves in the sandbag bunkers on the opposite bank. Gu Zhang stood at the bow, holding his shield high above his head, arrows from the opposite bank striking the iron shield and sending sparks flying. When the ferry reached the shore, he was the first to jump off, his boots splashing up a spray of water as he stepped into the shallow water. Southern infantrymen on the south bank rushed out from behind the fortifications collapsed by the artillery fire, trying to push back the landing point before the Yan army could establish a firm foothold. Gu Zhang didn't give them that chance. He knelt heavily on the sandy beach, plunging his shield into the sand, his entire weight pressing down on the shield, the spearmen's spears thrusting outwards from above his shoulders. Several of the first Southern infantrymen who charged forward were knocked down by spears, leaving a crooked pile of corpses on the beach.

Zhao Laoliu jumped off the boat immediately afterward. He pushed the first bundle of gunpowder canisters under the wooden fence of the Southern Army's shore fortifications, pulled the fuse, and sparks hissed along the hemp thread towards the base of the fence. A dozen breaths later, a deafening explosion blew a gaping hole more than four zhang wide in the wooden fence. The second ferryboat followed closely behind, and Huo Zhen led his mounted archers to spread out from the beach to both sides. They fired arrows from horseback to suppress the Southern Army infantry charging from the flanks. The arrows, carried by the morning wind, pierced the soldiers' cotton armor, and screams rose and fell amidst the echoes of the explosions. Huo Zhen turned around on horseback and shouted in Mongolian to the ferryboats behind him. At the same time, the mounted archers behind him drew back their recurve bows, and a volley of arrows rained down on the direction where the Southern Army reserves were assembling, scattering the Southern Army captains who had just formed ranks. Mei Yin's central command was in complete disarray after a day of continuous artillery bombardment and landing assaults. The Southern army retreated from behind the fortifications, and the Yan army's follow-up ferries landed one after another.

After the beachhead on the south bank of the Huai River was captured, the Yan army immediately began constructing pontoon bridges. The engineering battalion used ferries as bridge piers, laying thick planks between the boats and securing them with ropes and chains. Within a day, two pontoon bridges were erected across the Huai River, allowing the entire army of 100,000 and its supply wagons to cross within two days and nights. As Shen Du crossed the pontoon bridge, he glanced back at the still-smoking ruins of the riverbank defenses on the south bank in the river breeze. A year ago, they had towed their wrecked boats across the river in the mud, only to be driven back by hunger and disease. A year later, the remaining stakes of the fortifications lay crookedly in the sand, the charred wood still bearing the marks of gunpowder. He didn't linger long.

Having crossed the Huai River, the Yan army did not repeat the mistakes of the previous year. Zhu Di bypassed Qimei Mountain, avoiding a protracted battle with He Fu in the mountainous region of Southern Zhili, and instead marched directly south from the plains, reaching the Yangtze River. After refilling the Yan army's supply lines with Southern army granaries captured along the way, their supply routes were never interrupted. By the end of June, the vanguard of the Yan army reached Guazhou Ferry, opposite Yangzhou. Zhu Neng, mounted on horseback, looked across the Yangtze River—the Southern army flags on the Zhenjiang city tower trembled in the river wind, and the surface of the Yangtze shimmered like golden scales in the afternoon sun. Before them was no longer a river like the Huai River, which could be dealt with locally, but a natural barrier stretching from north to south. But this time they brought boats. This time, there would be no turning back.