Inside a warm pavilion in Bianjing, Zhao Pu sat deep in thought.
Having once served as sole chancellor for ten years, Zhao Pu knew the state of the realm exceedingly well.
Since the mid to late Tang, the fact that the empire's finances and grain depended entirely on the southeast was no longer an empty phrase, but an objective reality.
And it was also a fact that Chang'an had fallen out of favor.
After the fall of Tang, Liang, Tang, Jin, Han, and Zhou, along with Min, Shu, Chu, Yue, and others, not a single regime established its capital in Chang'an.
Only the Shatuo tribe, descendants of the Western Turks, adopted the name Tang and set their capital in Luoyang.
Yet in Zhao Pu's view, this Shatuo Tang did not necessarily like Luoyang all that much. It was more about legitimacy.
After all, the imperial clan had no blood relation whatsoever to the Li Tang. They were naturalized Hu. If they took the Tang name yet set their capital elsewhere, it would have been hard to justify.
Even so, the Shatuo Tang emperors, just like the Li Tang emperors before them, had worried endlessly about food.
Prefectures rushing grain deliveries, immediately supplying the capital, the commissioners of taxation waiting outside the Shangdong Gate, calculating allocations as they arrived. This was no secret.
And as far as Zhao Pu knew, Li Cunxu had even considered going to Bianliang to beg for food.
But in the end, he feared that doing so would expose Luoyang's shortage of resources and trigger instability, so he accepted his ministers' advice to live frugally instead.
Thinking it over like this, Zhao Pu felt that the light screen's judgment on the decline of Chang'an and Luoyang did make a certain amount of sense.
Li Tang set its capital in Chang'an and went to Luoyang to eat.
Shatuo Tang set its capital in Luoyang and went to Bianliang to eat.
Now Song had set its capital in Bianliang, seemingly monopolizing the advantages of canal transport. Yet the final line on the light screen made Zhao Pu instantly alert.
The Jin dynasty swept straight in.
A dynasty named Jin. Zhao Pu searched his memory and found nothing. He flipped the paper in his hands, where he had hastily written down the dynastic names seen on the light screen.
Looking again at the division of Song into north and south, and then its eventual replacement by Yuan, Zhao Pu found himself completely unable to make sense of it all.
Subconsciously, he turned his gaze toward Zhao Kuangyin.
Care to explain, Your Majesty?
Zhao Kuangyin's mind was in chaos. He only waved his hand reluctantly, unwilling to discuss it for now, intending to think it through carefully on his own.
In truth, the idea of relocating the capital had been fermenting in his mind for some time.
When later generations discussed the various reasons for setting the capital, Zhao Kuangyin had initially treated it with a smile.
Relocating the capital is a matter of state. What do you know?
But watching the later generations lay out facts, analyze causes, and describe future consequences, Zhao Kuangyin began to sweat.
Relocating the capital is a matter of state. What do I know?
Then, glancing at his younger brother sitting opposite him with head lowered and face obscured, Zhao Kuangyin grew even more unsettled.
Yet he did not show it. Instead, he nodded kindly at Zhao Pu.
"If Zeping has doubts, stay behind later and talk it through with me."
...
"Two pillars…"
Du Ruhui murmured the blunt yet perfectly apt phrase used by later generations.
"The center of military, governance, and finance…"
Fang Xuanling likewise savored the concise terminology and description.
The two senior ministers exchanged a glance, each arriving at a deeper understanding.
"The An Lushan disaster stemmed from relocating Hu populations, placing Hebei under constraint. Once the rebels seized that region, they controlled half of Tang, and disaster was born."
"If our dynasty were to lose Hebei…" Du Ruhui stopped there, for the rest was all too easy to infer.
Rebels would demand reinforcements. Reinforcements would require higher taxes. With Hebei gone, everything would depend on the southeast.
Doubling corvée and taxation would breed resentment in the southeast, which would eventually erupt into chaos.
What was that term the later generations used again?
"A death spiral."
Wei Zheng inhaled sharply, recalling the simple yet thunderous words of the ancients.
"Within, there are no legalist ministers or loyal officials. Without, there are no powerful external enemies."
Li Shimin calmly provided the annotation.
"A state always perishes from within."
The later generation's account showed him the causes of Tang's fall from a remarkably clear angle.
Overcultivation of Guanzhong caused Yellow River siltation and obstructed canal transport.
The inward migration of Hu peoples destabilized Hebei, costing Tang half its realm.
When the people had nothing to eat, prosperity became a castle in the air, collapsing at the slightest touch.
Even so, Li Shimin still asked himself a question.
"How could Bianzhou serve as a capital?"
He was not unfamiliar with the place. As later generations said, it was a vital hub of southeastern canal transport.
During the Northern and Southern Dynasties, Chenliu had been divided into Liangzhou and Kaifeng Commandery. Later, Liangzhou was renamed Bianzhou. In early Sui, Bianzhou was abolished and merged into Xingyang, Yingchuan, and other commanderies.
But after the founding of Tang, Bianzhou was reestablished. Combined with the later generation's explanations, Li Shimin understood its location very clearly.
His first instinct was doubt. Chang'an lacked natural defenses only because Guanzhong had already been broken.
Guanzhong had Mount Long to the left and Tong Pass to the right. Luoyang had Chenggao to the left and Yao and Han Passes to the right.
But Bianzhou? To the north, there was not a single layer of natural defense.
Li Shimin felt that if he personally led cavalry, marching from Zhuo Commandery to Bianzhou would take at most five days.
And recalling the later verified Jingkang Disaster, Li Shimin shook his head repeatedly.
He did not know whether to admire the courage of the Song emperor or mock him for being book addled.
Virtue over terrain?
Without terrain, what virtue is there to speak of?
[Lightscreen]
[Climate's influence runs through the entire history of human civilization, spanning both Eastern and Western worlds, and extending even to the present day.
Just as canal transport was the lifeline of feudal empires, for ancient Rome, the Mediterranean held the same importance.
The difference was that the Mediterranean was shaped by nature itself, and thus reacted even more violently to climatic change.
This blessed bathtub allowed ancient Rome to forge its golden age, yet ultimately sounded its death knell as well.
Just as Emperors Huan and Ling witnessed the decline of the Han Empire, Marcus Aurelius, living in the same era, witnessed the elegy of ancient Rome.
During this period, Rome's population reached an unprecedented seventy five million, but soon afterward conditions began to deteriorate sharply.
The Antonine Plague and the Cyprian Plague we mentioned earlier were only part of it. The primary cause was climate change.
Roughly at the same time that Chancellor Zhuge passed away at Wuzhang Plains in the autumn wind, Rome's warm period also officially ended. A cold backlash began its counteroffensive.
The warm, humid, and stable climate of Rome's golden age vanished, replaced by cold, arid, and highly volatile conditions.
As with ancient China, the most direct impact was a drastic decline in grain production.
Do you remember Cyprian, the bishop of Carthage who gave his name to the Cyprian Plague? His surviving manuscripts recorded climatic changes in North Africa as well:
"Rainfall has become exceedingly scarce. The land grows increasingly barren, and crops grow far more slowly than before."
If Tang's prosperity relied on Hebei and Jianghuai, then Rome's prosperity was built on Egypt, a heaven bestowed granary.
But as the climate changed, the Nile's flow was cut nearly in half, sharply reducing Egypt's grain output.
The drastic fall in agricultural production left Rome stretched thin. The Cyprian Plague left it reeling. The internal turmoil that followed delivered the final blow.
In 251, Sima Yi died, and the Roman emperor Decius was slain by the Goths at the Danube.
The following year, Ardashir's son, Shapur, emperor of the Sassanian Persian Empire, successfully counterattacked Rome, seized Syria, and ravaged Asia Minor.
At the same time, the northern Goths were far from idle. They swept into the Aegean and Black Sea regions, looting extensively.
Seven years later, the commander of Rome's Gallic legions proclaimed himself emperor and seceded from the Roman Empire. This emperor likely would have found much common ground with Zhao Da.
Constrained by threats from the Franks and Alemanni to the north, Rome begrudgingly recognized the independence of the Gallic Empire and even allied with it.
Yet Rome still suffered repeated defeats at the hands of the Franks.
Fairly speaking, when faced with the end of its golden age, some Roman emperors did attempt to prolong the life of this vast empire. But with agriculture fundamentally crippled by climate, these reforms were more or less ineffective and triggered unpredictable consequences.
In 293, to cope with the endless external threats of a massive empire, Emperor Diocletian instituted the Tetrarchy, dividing Rome into eastern and western halves, each ruled by two emperors who checked one another. This system collapsed rapidly after Diocletian's death, giving rise to Eastern and Western Rome.
Over the next two hundred years, Roman and Chinese emperors faced similar problems: declining agricultural output, rampant rebellions, massive conscription, and ever worsening agriculture.
The difference was that Rome's emperors, confronted with boiling resentment and natural disasters, ultimately issued the decree to abolish all other faiths and establish Christianity as orthodox, binding empire and church tightly together.
Not until the sixth century did this prolonged cold period finally end, ushering ancient China into the brilliant Sui and Tang era.
Rome followed a similar path. Emperor Justinian swore to restore Roman glory and launched a sweeping reconquest.
But a sudden massive volcanic eruption shattered Justinian's dream. Mediterranean climate plunged back into chaos, widespread plague returned, and the dream of restoring Roman glory was extinguished. The power of the church flourished.
The abruptly worsening climate also forced the Arabs out of their barren deserts, igniting the sweeping Islamic conquests and completely crushing Rome's hope of revival.]
"Seventy five million people…"
Liu Bei was the first to be stunned by the sheer scale of that population, followed immediately by a feeling of envy.
"Could the Mediterranean truly be more bountiful than land and rivers?"
He said so, yet he knew it was a meaningless question.
From the Spring and Autumn period onward, canals had been dug endlessly. Then there were the massive canals of Sui and Tang. Fundamentally, was this not dissatisfaction with the inconvenience of river transport?
Still, Liu Bei remembered that in his childhood in Zhuo Commandery, he often heard tales of the eastern sea's fickle climate swallowing people whole. Many commoners were instinctively wary of the ocean, and he was no exception.
But now it seemed that the Mediterranean was not the same as the eastern sea he had feared as a child.
"That region is vast, relying on the advantages of the Mediterranean while neglecting land based defenses. It is thus unsurprising that external threats arose repeatedly."
Kongming stared at the map, deep in thought.
Maps from later generations were often highly simplified, yet they omitted no crucial information. From them, the general terrain of ancient Rome was immediately apparent.
Mountainous and hilly along the coasts, broad plains to the north. These so called Goths and Franks. How were they any different from the Hu faced by the Han people?