Li Shimin's expression grew steadily darker.
The Tang dynasty might enjoy a reputation for martial prowess, but to the west lay Tubo, and to the north the Turks—each like a festering parasite clinging to the bone.
Tubo could at least be excused somewhat. Climate shifts were beyond anyone's foresight, and its ruler was increasingly adept at concealment, while its chief minister harbored the heart of a jackal and a fox.
But the Eastern Turks—those were a disaster he had personally engineered.
Assassination attempts by the Turks had forced him into hesitation and retreat. Releasing them back to their old lands had not brought peace, but instead planted a calamity that would last a century.
From this, Li Jing easily sorted out the pattern of the northern frontier:
"Destroy the Turks, and Xueyantuo rises. Destroy Xueyantuo, and the Turks grow powerful again. The northern border has never truly known peace."
He could not help but sigh afterward.
"Pei Xingjian… what a difficult burden he bore."
Only now did they understand why the light curtain had earlier made a point of emphasizing logistical support.
Those three hundred thousand troops—most of them, it turned out, had been chasing Turkic cavalry on foot.
Infantry pursuing cavalry. The Turks naturally exploited their mobility, circling around to strike the baggage trains.
Uneven troop quality. Too few horses. Inadequate supplies. Supply lines under constant threat.
And yet, despite all this, they still achieved a great victory.
Seen in that light, Pei Xingjian's grasp of military strategy could only be described as breathtaking.
Anyone who truly understood warfare arrived at the same conclusion instantly. A smile crept onto Su Dingfang's lips. Li Shiji, on the other hand, felt a little uncertain.
Could it be… that I'm actually the weakest one here?
Setting aside his obsession with the Turks, Li Shimin offered a sincere compliment:
"These Tang beacon towers—there is real ingenuity in them."
To Li Shimin, innovation that belonged to Tang itself mattered immensely.
Studying the diagrams and explanations of the beacon towers on the light curtain, Li Jing nodded in approval as well:
"The placement of the smoke-and-fire point is superb—isolated terrain, stocked with dry rations and fresh water. When on duty, even if attacked, the soldiers can cut the rope ladder and hold the position."
"One thousand eight hundred beacon towers. Five men per tower. Not even ten thousand men total. Add ten thousand cavalry as mobile defenders, moving the moment smoke is sighted to hunt down the enemy."
"This Zhang Renyuan—his mind is exceptionally sharp."
By now, Du Ruhui had also grasped the underlying logic.
Raising three hundred thousand troops accomplished little—only forcing the Turks into submission one year, rebellion the next, raiding endlessly.
But a mere thousand-plus beacon towers could lock the Turks firmly north of the desert, unable to step south even once.
From the founding of Tang through the Zhenguan era, fierce generals had emerged in abundance, brilliant achievements piled atop one another.
Yet behind every dazzling military star stood the quiet, unseen labor of men like Zhang Wansui.
To those gathered in Ganlu Hall, Tang beacon towers were a source of pride.
After all, Tang was now the one doing the striking—not the one being struck.
But when the beacon towers evolved into signal towers, everyone was stunned yet again.
"This… was derived from beacon towers?"
Fang Xuanling asked instinctively, then answered himself:
"Indeed. Built every few li, passing signals from tower to tower."
"These wooden semaphore arms transmit messages decoded by a codebook—much like battlefield flag signals. Combined with beacon principles, they achieve such results."
"Only…" Fang Xuanling frowned at the twisting foreign script in the example diagrams on the light curtain.
"If it were Chinese characters, how would one convey them?"
Li Shimin had already risen to his feet, unconsciously imagining the spectacle—if messages could travel from Chang'an to the Western Regions in this way, what grandeur that would be.
Du Ruhui, meanwhile, seemed to glimpse a clear lineage: from Han beacon towers, to Tang beacon towers, and then to these later signal towers—continual refinement through technique and learning, each generation more effective than the last.
Was this not what later ages called "science"?
This invisible yet undeniable thread of progress reminded Du Ruhui of a line from the Book of Changes:
"When things reach an extreme, they change. Through change, they find continuity. Through continuity, they endure."
He then added his own thought:
"And when endurance reaches its limit, it again changes—changes, continues, endures, and once more reaches its limit."
"The only law that never changes is the law of change itself."
Yan Lide, ever practical, immediately focused on the mention of telescopes. After all, it was he who had approved the transparent glass supplied to the Imperial Academy.
Judging by the tube-like shape depicted, a clear research direction had already formed in his mind.
[Lightscreen]
[Another sign of Tang military decline under Gaozong lay in the lack of capable commanders.
Su Dingfang, Li Shiji, Liu Rengui, Pei Xingjian, Xue Rengui—nearly all of them can be counted as the political legacy of the Second Phoenix.
They were promoted by Li Zhi, but not discovered by him.
Yet when one looks at history, the martial examinations began during Li Zhi's reign. Which naturally raises a question:
Did the Tang martial examinations truly fail to produce talent?
Wei Yuanzhong—who had earlier advised lifting the horse ban—had cursed this as well. And he did not curse the martial examination alone, but the entire examination system.
Civil officials were selected solely on literary flourish, without testing governance or statecraft—producing nothing but eloquent windbags.
Military officials were selected solely on riding, archery, and brute strength, without testing strategy or command—producing nothing but big, strong fools.
Wei Yuanzhong was not wrong.
Look at the Tang martial examination subjects, for example:
If Lü Bu took it, he would certainly place first. If Zhuge Liang took it, his results would be mediocre.
The martial examination tested seven items: fixed-target archery, mounted archery, mounted spear, foot archery, physique and appearance, speech, and weightlifting. At least five had to score "upper grade" to pass.
Fixed-target archery involved three targets at different ranges, each scored by rings.
The rest were self-explanatory.
Military strategy? None.
For this reason, even the Song dynasty later felt free to mock Tang's martial examinations.
When Ouyang Xiu compiled the New Book of Tang, his evaluation was blunt: "Not worth mentioning."
Li Zhi surely understood these flaws. But for various reasons, he praised Wei Yuanzhong's proposals—then chose not to adopt them.
It was not until the Kaiyuan era that Emperor Xuanzong finally patched this hole and reformed the martial examinations.
From this, Tang at last produced a single towering military talent of its later years: Guo Ziyi.]
"Xuanzong truly deserves the title of 'a sage for half a lifetime,'" Fa Zheng remarked.
The later generations' judgment did seem fair. These measures did qualify as enlightened rule.
And yet, the more so, the more fractured the image became—how could such a brilliant man, in his later years, end up like that?
"Li Zhi really had it easy," Zhang Fei declared, feeling he had seen through it all.
"He spends his father's money, marries his father's wife, and leaves the mess for his descendants to clean up."
"Truly a comfortable life."
Liu Bei could only laugh helplessly. Something about that sounded wrong—but it also wasn't exactly wrong.
"All the same," he cautioned, "Third Brother, your words are a bit too crude."
Then Liu Bei smiled and asked:
"With Tang's martial examinations, would the Strategist place first?"
Zhuge Liang, teased by the light curtain and now by his lord as well, waved his feather fan without a hint of modesty.
"If crossbows were permitted," he said calmly, "Liang would certainly take first place."
Laughter immediately filled the Chengdu prefectural hall.
Drawing a bow required strength. Zhuge Liang, burdened with governance, trained regularly but could hardly match fierce generals in raw power.
Zhang Fei beamed.
"Then if it were me, wouldn't my name surely make the list?"
Fa Zheng counted on his fingers.
"Weightlifting, foot archery, mounted spear—these three, General Yide should score well."
Zhang Fei corrected him proudly. "Not just well—top marks!"
Fa Zheng nodded.
"Physique and appearance we'll skip."
"Fixed-target archery could be trained. Mounted archery is harder—it requires long practice."
Zhang Fei counted along. "That makes four. Only speech remains—so wouldn't that mean…"
Fa Zheng shook his head, smiling.
"For speech, General Yide need only say three sentences."
Zhang Fei nodded.
Fa Zheng's tone suddenly turned serious.
"Three sentences—and the examiner will fly into a rage and expel you."
Zhang Fei froze. The hall erupted in laughter.
[Lightscreen]
[Another often-overlooked factor in the rise and fall of Tang military power was the crossbow.
In the age of cold weapons, the crossbow carried several defining traits:
Easy to learn, powerful, hard to maintain, and expensive.
As such, it could only ever be controlled and manufactured by the state.
Even during the fubing era, crossbows were prohibited weapons for soldiers—ranked alongside armor. Only after armies assembled were the arsenals opened and equipment issued.
In Tang's foreign wars, enemy forces rarely carried shields or formed dense formations. Archers lacked conditions for massed volley fire.
Under direct fire, crossbows were more accurate and had longer range than bows, making them preferable.
This is why Li Jing stipulated that crossbowmen could fire at one hundred and fifty paces, while bowmen had to wait until the enemy closed to sixty steps. Tang armies did not rely on massed arc fire.
Under Gaozong, recruitment numbers kept rising, but troop quality varied wildly. These recruits lacked the lifelong archery training of fubing soldiers.
Logically, this was when crossbows should have been deployed in greater numbers to stabilize combat effectiveness.
But Gaozong being Gaozong… reducing expenses was already generosity. Increasing funding was unthinkable.
Thus, as soldier quality declined and no money was spent to compensate elsewhere, Tang military performance steadily worsened.
Once again, Xuanzong provides the contrast.
By his reign, the fubing system was nearing collapse, and the army consisted mainly of recruits. Under such conditions, Xuanzong spared no expense on crossbows.
Wang Zhongsi's great victory at Yubiaochuan relied on crossbows. Xiao Song's triumph at Qilian City depended on four thousand crossbowmen.
During the Kaiyuan era, Jiang–Huai crossbow units became elite troops renowned throughout the realm.
Whenever crossbows are mentioned, one inevitably arrives at the Song dynasty's Divine-Arm Crossbow.
But upon closer inspection, the limitation of crossbows was never power.
Tang military theorists already noted: in battle, one or two shots at most.
The true limitation was reload speed. Accordingly, crossbow evolution focused almost entirely on solving this flaw.
First came the belly-drawn crossbow, braced against the abdomen to span the string.
This evolved into belt hooks, using the waist to generate force.
Then came the foot-drawn crossbow, with a stirrup at the front—the Divine-Arm Crossbow belongs to this category.
Later, the West applied physics to the problem, inventing windlass crossbows and lever crossbows (the "goat's-foot" crossbow).
After steel crossbows appeared, further refinements led to self-spanning lever crossbows, giving rise to crossbow cavalry.
On the individual level, hand-cranked gear-driven steel crossbows emerged—absolute killing machines.
In summary, the Divine-Arm Crossbow was the pinnacle of classical Chinese crossbow design.
But constrained by scientific development, it was far from the true pinnacle of the crossbow.]