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

In the autumn of the eleventh year of the Yongle reign, in Hami.

Shen Du stood on the city wall of Hamiwei, facing the boundless Gobi Desert. The setting sun dyed the sand and gravel a dark red, while the distant snow-capped peaks of the Tianshan Mountains gleamed with a cold golden light in the twilight. They had trekked across the Gobi for nearly two months from Jiayuguan to Hami. Half of the fresh water they had brought with them had been used up when they crossed Xingxingxia Gorge. Zhao Laoliu's lips were so cracked he could barely speak, so he used his eyes to direct the camel caravan to redistribute the water bags, rationing three bowls per person per day—one for drinking, one for cooking, and one for the camels carrying surveying equipment. Two camels collapsed while crossing a salt flat. Zhao Laoliu squatted beside them, his pipe in his mouth without lighting it, remaining silent for a long while before standing up and ordering the equipment from the camels to be distributed to the other animals. Then they continued on their way.

The walls of Hami Garrison were built during the Hongwu era using rammed earth. The walls were no more than 25 feet high, and the foundation was riddled with holes from wind and sand erosion. Half of the parapet on the east side had collapsed, and a crack ran from top to bottom above the gate on the west side. The garrison inside numbered less than 800 men, with only about 60 muskets still operational, and less than three months' worth of provisions. However, this garrison was strategically located at the easternmost point of the Western Regions, the first Ming Dynasty garrison west of Jiayuguan, and the eastern gateway to the entire Western Regions defense system.

Shen Du walked around the city wall, marking the damaged sections, garrison strength, food supplies, and water sources on the map with charcoal. He squatted down and touched the base of the rammed earth wall—the soil was loose and severely eroded by wind; if the outer wall wasn't reinforced with bricks, this section would collapse from the base in a few years. "The city wall must be reinforced with blue bricks," Shen Du said, standing up, tucking the charcoal pencil behind his ear, and turning to the clerk behind him. "Keep the rammed earth core, and build a layer of blue bricks on the outside, grouting the joints with glutinous rice mortar. Transporting bricks from Jiayuguan is too expensive; they have to be fired locally."

Old Zhao squatted at the foot of the city wall, grabbed a handful of sand from beside the foundation, rubbed it in his palm, and then smelled it. "The local soil is too alkaline; the bricks made from it will easily crumble. But there's a riverbank twenty miles to the east with better soil, more sticky enough. We can dig it up and build a kiln there. When firing the bricks, mix one-tenth of the soil with the fine sand from the riverbank, and the brick blanks won't crack easily." He scattered the sand on the ground, stood up, clapped his hands, and said, "Give me two hundred craftsmen and three thousand laborers, and within six months, cover the entire city wall of Hamiwei with bricks, and reinforce the corner towers at the four corners." His pipe bowl was dangling from his mouth, the smoke flickering in the evening breeze. From Beijing to Liaodong, from Liaodong to the coast, from the coast to the Western Regions, he had repaired countless city walls and watchtowers. Whenever he moved to a new place, the first thing he looked at wasn't blueprints, but the actual construction. He no longer needs blueprints to determine what kind of bricks to fire and what kind of walls to build.

Shen Du nodded and turned to look at Su Wanqing standing behind him. She was squatting beside an abandoned vegetable garden inside the city wall, pinching a clod of soil in her hand, smelling it, then dipping her finger in it and tasting it on her tongue before standing up and patting the soil off her hands. "This land is arable. The soil is sandy loam, which drains well. Although the alkalinity is a bit high, it will come down after two seasons of irrigation. There's an old canal outside Hami City where snowmelt flows down from the mountains. The canal is still there; after dredging, it can be used to irrigate the fields. Give me two thousand mu of farmland, and within three years, the Hami Garrison will be self-sufficient in military rations."

"The existing military households in Hamiwei are not enough. We need to recruit immigrants from within the Great Wall, or transfer a group of military households from Shaanxi and Gansu," Shen Du said.

"I've already had the Ministry of Revenue check. The population in the Shaanxi-Gansu area has grown rapidly due to tax reductions in recent years, resulting in a considerable surplus of labor. We can relocate two thousand households here, each receiving fifty mu of land, three shi of seeds, and a set of farming tools, with a three-year tax exemption. The first batch of immigrants will depart next spring and arrive by summer." Su Wanqing pulled a roll of paper from her sleeve and handed it over. On it, written in neat small characters, was the "Hami Garrison Irrigation and Land Reclamation Plan"—clearly outlining how to construct irrigation canals, how to divide the garrison land, how to resettle immigrants, and the routes for allocating seeds and farming tools. Even the supply plan for the post stations along the route from Shaanxi-Gansu to Hami was included. Shen Du read the plan from beginning to end, mentally calculated the time and manpower, and then looked up and said, "The construction of the city and the garrison land reclamation will proceed simultaneously. Zhao Laoliu will be in charge of the city walls and brick kilns, and you will be in charge of water conservancy and land reclamation. I will submit the surveying and troop deployment to Beijing after I complete them."

Turpan, the twelfth year of the Yongle reign.

Traveling west from Hami, the surveying team traversed hundreds of miles of Gobi Desert and oases to reach Turpan. This fiery land was even hotter than Hami; in the sweltering summer afternoons, it was hot enough to cook an egg on the ground. Zhao Laoliu placed an egg on a stone of the city wall, and the egg white solidified in less than the time it takes for an incense stick to burn. Turpan's city walls were older than Hami's—the rammed earth walls left from the Yuan Dynasty had been worn smooth by wind and sand, resembling a low, yellowish-brown embankment from afar. However, the irrigation system here was more advanced than in Hami. Karez wells stretched from the foot of the snow-capped mountains all the way to the depths of the oasis, the water in the underground channels cool and sweet; a handful washed on the face could wash away half the day's heat. The local chieftain of Turpan received them and led Shen Du and his group down into the underground culverts to see the structure of the karez wells. Zhao Laoliu squatted beside the well, used a long bamboo pole to probe the water level in the underground channel, and turned to Shen Du, saying, "This karez well is superior to the open channels in our inland areas—the water doesn't evaporate when it flows through the underground channel, and less than 20% of the water is lost from the snow-capped mountains to the oasis."

Shen Du squatted at the outlet of the karez well, cupped his hands, and drank the water. It was sweet. "Draw a diagram of the karez well's structure; it will be useful for water conservancy projects in Hami and other garrisons in the future." The clerk opened a blueprint and sketched a cross-section of the karez well on the paper with charcoal. Su Wanqing stood silently beside him until the drawing was finished, then spoke: "After we return, I will petition the Ministry of Revenue to send water conservancy craftsmen to the Western Regions to learn the karez well technology and bring it back to Shaanxi and Gansu."

Continuing west from Turpan, they arrived at Yilibali. This was the westernmost major city in the Western Regions; further west lay the sphere of influence of the Timurid Empire. Yilibali's city walls were made of stone, and the city was a bustling marketplace where Hui merchants, Mongol herdsmen, Han soldiers, and people speaking various languages ​​mingled. Standing atop the city walls of Yilibali, Shen Du looked westward. The setting sun was painting the distant snow-capped mountains and desert in gold; that was the edge of the Ming Dynasty's sphere of influence—beyond that, the Ming Dynasty's rule ended.

"The defense system of the Western Regions, from Hami to Turpan and then to Yilibali, is a line." Shen Du spread the last page of the general map of the Western Regions on the table. The firelight reflected the mountains, rivers, and garrison markings on the paper. "Each city along this line cannot fight alone. Hami is the eastern gateway, Turpan is the central hub, and Yilibali is the outpost. There must be regular patrols of cavalry and beacon fires between the three cities. If one city is alerted, the other two cities can send troops to support it within half a month. Hami's city walls, after being reinforced with bricks, can withstand the first wave of attacks. Turpan's karez wells and agricultural settlements can support a long-term garrison. Yilibali's stone walls can serve as a bridgehead. With these three cities linked together, the Western Regions are the Western Regions of the Ming Dynasty."

He put down his pen and looked up at Su Wanqing, Zhao Laoliu, Gu Zhang, and Huo Zhen sitting opposite him. These people had followed him from Beijing to the Western Regions for several years, wearing out dozens of pairs of boots, drawing countless maps, and building dozens of cities. "It's time to go back." Shen Du stood up and walked to the tent entrance, looking eastward, where the sky was already turning a pale white. "We've been out here for two years."

Spring of the thirteenth year of the Yongle reign, Beijing.

When Shen Du entered the Fengtian Hall, Zhu Di was reviewing memorials. The crabapple blossoms outside the hall were in full bloom, their petals falling onto the stone steps in the spring breeze, which several eunuchs were gently sweeping with bamboo brooms. Seven years had passed; Zhu Di's temples were mostly white, and the wrinkles around his eyes were much deeper than when he was in Nanjing. But his back remained ramrod straight, his wrists still strong, and his vermilion brushstrokes for reviewing memorials were still powerful and penetrating.

"Your subject, Li Jingzhong, has completed the surveying and mapping of the defenses of the Western Regions and coastal garrisons, as ordered by imperial decree." Shen Du knelt on one knee, presenting a thick stack of maps with both hands. The eunuch took the maps and placed them on the imperial desk. Zhu Di opened to the first page—the first page of the complete map of the Western Regions. From Jiayuguan westward to Yilibali, every city, river, oasis, and desert was clearly marked with extremely fine strokes. He turned page after page, reviewing the joint defense maps of Hami, Turpan, and Yilibali in the Western Regions. He then reviewed the general maps of the coastal garrisons of Shanhaiguan, Dengzhou, Zhoushan, and Quanzhou, finally turning to the last page of the "General Map of Northern Frontier Defenses."

That page depicted the complete Great Wall defense line from Juyong Pass to Jiayu Pass. North of the Great Wall, it marked the nomadic areas of the Tatars and Oirats, the distribution of water sources, and possible southward routes for their cavalry. South of the Great Wall, it marked the military settlements, granary locations, and garrison deployments. In the lower right corner was a line of small print: "The threat from the northern barbarians lies not within the walls, but outside. To defend within the walls, one must know what lies outside." Below this was the seal of Li Jingzhong.

Zhu Di stared at this page for a long time. Then he closed the drawing, looked up at Shen Du, and said, "You've spent two years in the Western Regions, a year along the coast, half a year in Liaodong, and three years in the Northern Frontier. From the first year of the Yongle reign until now, you've been traveling for almost ten years." He paused, a hint of something unspoken in his voice, "When I first met you at the Baigou River, you were just a greenhorn, newly promoted from a junior officer to a senior officer. Now your hair has turned white."

Shen Du remained silent. He found himself looking at the crabapple tree in the courtyard outside the palace. The petals were very white, almost translucent in the sunlight, falling with the slightest breeze, landing on the stone steps, in the damp mud swept by the broom. He suddenly remembered the reed marshes along the Baigou River, the young faces trampled into the mud by horses' hooves as they fled past him, Zhao Laoliu squatting on the ground tasting the soil in Hami, and Su Wanqing standing in the desolate wilderness of western Liaoning, reaching out her hand to a group of military families' families wrapped in headscarves.

Zhu Di stood up from behind his desk and walked to Shen Du. "I have seen every single map you have drawn over the years. I have approved every single one of your strategies. You said the northern frontier needed in-depth defense, so I established the Liaodong Regional Military Commission and the Datong Garrison. You said the coast needed patrols at sea, so I ordered the navy to sail regularly. You said the Western Regions needed a three-city joint defense, so I had the Hami Garrison, the Turpan Garrison, and the Yilibali Garrison support each other. But today I don't want any strategies. I only want to ask you one question."

He looked down at Shen Du. "You have traversed every border region of the Ming Dynasty. Tell me—can this vast land be defended?"

Shen Du raised his head to meet Zhu Di's gaze. The hall was quiet, save for the sound of crabapple blossoms falling in the wind outside. "Your Majesty," he said, his voice not loud, but each word as steady as when he uttered the military pledge at the Baigou River drill ground, "walls may age, bricks may crumble, and cannons may become obsolete. But people can remain. If the farming households don't leave, if the soldiers guarding the cities don't leave, if the mapmakers don't leave, then this land will be protected. In the northern frontier, I've seen children of military households learning to read under beacon towers; in Dengzhou, I've seen fishermen voluntarily taking the naval outposts; in Hami, I've seen immigrants harvesting their first wheat and delivering it to the garrisons. As long as these people are here, this land will remain."

Zhu Di remained silent for a long time. Then he placed his hand on Shen Du's shoulder. That hand was much older than when he had supported him at the foot of Jinan City years ago; the wrinkles on the back of the hand resembled a dried-up riverbed, but the palm was still warm and steady. "Go. Finish painting what you haven't finished. I want you to watch over this land for me."

When Shen Du emerged from the Fengtian Hall, Zhao Laoliu was squatting beside the stone lion outside the Meridian Gate, a pipe dangling from his mouth, a freshly baked sesame cake in his hand. Su Wanqing stood beside him, carrying a newly prepared box of ointment and a newly made cotton armor. She had just arrived at the Meridian Gate that morning from the Ministry of Revenue; the armor was hand-sewn, the stitches uneven, but made from the finest Songjiang cotton. Gu Zhang stood a little further away with several old comrades; his old left arm injury still ached on cloudy days, but he stood ramrod straight. Huo Zhen's son, Batu, waited even further away with the riders of the Duoyan Three Guards, leading their horses.

Shen Du took the sesame cake from Zhao Laoliu, stuffed the plaster Su Wanqing gave him into his pocket, draped his cotton armor over his arm, and mounted his horse. The horse was an Ili horse brought back from the Western Regions, taller than a Mongolian horse, its mane swaying slightly in the spring breeze. He glanced back at the glazed tile roof of the Fengtian Hall, then turned his horse and headed west. Zhao Laoliu followed behind on his donkey, a pipe dangling from his mouth, the donkey carrying surveying equipment and dry rations. Su Wanqing stood outside the Meridian Gate, watching his figure gradually shrink, tucked a stray strand of hair behind her ear, and turned to walk towards the Ministry of Revenue. She had to review the resettlement plans for the new batch of Western Region immigrants that afternoon.

From Baigou River to Nanjing, from Beijing to the coast, from the coast to the Western Regions—the road he had traveled was longer than any line on a map. But he knew the journey was not yet over.