The Prince of Dai was gravely ill, and the divine physician prescribed a remedy.

The making of horseshoes was a simple task, and so within a few days, the entire batch was completed. Li Jing summoned Li Zhi once again to instruct everyone on how to attach the horseshoes. To their surprise, installing the horseshoes was exceedingly simple. One only needed to adjust the arc of the horseshoe slightly to fit the shape of the horse’s hoof, and then nail it onto the hoof with iron nails. Such work required no specialist; even the soldiers themselves could easily manage it.

Soon, all the warhorses that had not been injured were fitted with horseshoes. As for the injured horses, once their hooves regrew their keratin layer, they too would be able to wear them. In fact, the area where the horseshoe is attached is much like a human fingernail—a keratinous layer—so the horse feels no pain during the process. With the protection of the horseshoes, the horses’ hooves no longer needed to fear wear and tear. Over time, it would even become necessary to trim their hooves, lest the keratin grow too long.

After several days of observation, Li Jing finally confirmed the effectiveness of this method. He immediately reported his findings to Emperor Taizong. Upon hearing Li Jing’s account, Emperor Taizong was delighted. “It can be done so simply? Will it truly preserve our warhorses?” he asked.

Li Jing replied, “Your old minister has carefully observed the results—this method is indeed remarkably effective.”

Emperor Taizong laughed heartily, “Excellent! Since this method works, notify the entire army to implement it at once.” Then, turning to Li Jing, he praised, “My loyal minister, you manage affairs of state and oversee the new army, and yet you still devise such a clever solution. You are truly the pillar of my reign!”

Li Jing, slightly embarrassed, replied, “Your Majesty, you give me too much credit. This method was the idea of the Prince of Jin; I can claim no credit for it.”

Emperor Taizong exclaimed in surprise, “Zhinü again? He has had little contact with warhorses; how did he devise such a plan?”

Li Jing explained, “Your Majesty, the Prince of Jin reasoned that warhorses, like people, should wear shoes for better running.”

Emperor Taizong was briefly taken aback, but soon grasped the logic. He laughed, “So that’s it! Pity that none of us, who deal with warhorses daily, ever thought of such a thing.”

Li Jing bowed, “This old minister is ashamed.”

Emperor Taizong waved a hand, “There’s no need to blame yourself. It seems we all fell victim to tunnel vision.”

Li Jing said, “The Prince of Jin’s thinking is indeed original; I am not his equal.”

Just as Emperor Taizong was about to inquire further about the Dragon Cavalry, a commotion suddenly arose outside the Hall of Supreme Harmony. Emperor Taizong frowned, about to rebuke the disturbance, when Zhang Anan, the attendant at the door, had already gone to investigate. Moments later, Zhang Anan returned, visibly flustered. “Your Majesty,” he announced, “the Prince of Dai is critically ill; the imperial physicians are at a loss.”

Emperor Taizong’s expression changed at once. He hurriedly rose and strode outside, anxiously issuing orders as he went, “Quickly, summon the Divine Physician Sun to examine him!”

Zhang Anan rushed off to carry out the command, while Emperor Taizong strode swiftly toward the inner palace.

In a side room of the Hall of Gentle Harmony, a boy of about two years old lay quietly in bed. His face was flushed with an unhealthy red, his breathing rapid and shallow, interrupted by frequent, urgent coughs. If one listened closely, a rattling sound could be heard in his breath. This child was Li Jian, recently granted the title Prince of Dai. At his bedside, a simply dressed beauty wept softly—his mother, Consort Lin. Also present were an imperial physician and two palace maids. The physician frowned in deep thought, trying to devise a prescription to ease the boy’s condition, while the maids stood by nervously.

At that moment, Emperor Taizong entered with Empress Zhangsun at his side. The Empress hurried to comfort Consort Lin in hushed tones. The Emperor stepped to the bedside and asked the physician, “How fares the Prince of Dai? Do you have a cure?”

The physician, fearful, knelt and replied, “Forgive your humble servant, Your Majesty. I am powerless; I have not yet found an effective remedy.”

Emperor Taizong frowned and motioned him aside, then quickly approached Li Jian’s bed. The child had already fallen into a troubled sleep, his face contorted in pain, his small body shivering with chills. Seeing the Emperor draw close, Consort Lin cried out, “Your Majesty, please protect your health and do not come nearer. Jian’er’s illness is highly contagious.”

Emperor Taizong waved her off, “Do not worry, beloved consort. I have already sent for Divine Physician Sun.”

“Thank you, Your Majesty,” Consort Lin replied, her voice trembling.

Emperor Taizong reached out to feel Li Jian’s forehead, asking, “How many days has he been ill? How did it become so severe?”

Consort Lin answered, “He fell ill quite suddenly two days ago. The illness is fierce and caught me completely unprepared.”

Empress Zhangsun interjected, “Has he taken any medicine these past two days?”

Consort Lin, still weeping, replied, “The physicians have prescribed remedies, but none have been effective.”

While they spoke, Zhang Anan hurried in with Sun Simiao. Zhang Anan was about to announce their arrival, but Emperor Taizong spoke first. “Divine Physician Sun, please examine the child at once.”

Sun Simiao agreed and quickly approached the bedside. He took Li Jian’s pulse, then carefully observed his tongue and eyelids. Only then did he turn to Emperor Taizong, frowning slightly. “The Prince of Dai is suffering from a cold-induced lung ailment, and it has become quite severe.”

Emperor Taizong asked anxiously, “Is there a remedy, Divine Physician?”

Sun Simiao replied, “Had it been earlier, I might have been uncertain. But thanks to the Prince of Jin’s methods, I have recently made breakthroughs in my medical understanding.”

Emperor Taizong was amazed. “Zhinü possesses such abilities?”

Sun Simiao explained, “The Prince of Jin invented the microscope, giving myself and the scholars of the Imperial Medical Academy the opportunity to observe bacteria directly. He also boldly proposed methods of analysis, allowing us to gain a deeper understanding of medicinal herbs.”

Emperor Taizong, intrigued, ventured, “Are you referring to chemistry?”

Sun Simiao nodded. “Indeed. This approach, combined with physics, has benefited us greatly.”

Overjoyed, Emperor Taizong exclaimed “Excellent!” several times, then quickly urged, “Please, Divine Physician, administer the medicine at once, so my son need not suffer longer.”

Sun Simiao at once wrote a prescription and instructed a palace maid to fetch the ingredients.

At that moment, the imperial physician who had been standing aside suddenly spoke. “Divine Physician Sun, may I see your prescription? I wish to learn from your expertise.”

He was intensely curious, for Sun Simiao’s diagnosis matched his own, yet the treatments he had tried had been to no avail, while Sun Simiao seemed untroubled by the case. He could not fathom the reason. After all, this illness had become widespread, and every physician had mastered the standard treatments. Yet with those methods proving ineffective, Sun Simiao was still able to prescribe with confidence—how could one not be curious?