Beneath the walls of Jiangning, the atmosphere in the Song army's main camp had grown noticeably more relaxed.
Anyone with eyes could see that Southern Tang's only real advantage had been the natural barrier of the Yangtze River.
Yet General Cao had first feigned a river inspection before secretly crossing at Hukou. Then came successive victories at Chizhou, Tongling, Wuhu, Dangtu, and Caishiji. In the end he forced a full crossing of the Yangtze itself.
Once the river had been breached, that so called heavenly barrier ceased to exist.
Before the crossing, the two sides had struggled for months. After the crossing, it had taken less than a single month for Song troops to surround the Southern Tang capital.
Still, because the campaign had advanced so rapidly, even the final river crossing had relied on seizing the right timing. Under such circumstances, it had been impossible for the Song army to carry elaborate siege engines.
Thus, when faced with Jiangning's formidable defenses, the only viable strategy had been encirclement and reinforcement denial.
Even so, Cao Bin had repeatedly encouraged his officers, declaring that Jiangning would fall within the year.
The claim sounded outrageous.
Yet no one under his command doubted it.
Against such a fortress, as long as the defenders' morale held, holding out three to five months would be effortless. Even lasting a year or more would not be unusual.
Situations like the Three Kingdoms tale of Lü Meng crossing the river in white robes and receiving Mi Fang's surrender, causing a stronghold to fall in a single day, were the rare exceptions.
For that reason, when Cao Bin heard the newcomer boasting about a miracle weapon, he did not believe it in the slightest.
But curiosity still stirred.
"Where is this weapon? Take me to see it at once. If it does not match your claims…"
He trailed off.
Punishing the man would be difficult.
Though commanding troops in the field, Cao Bin exchanged letters with the Emperor every other day, so he knew a fair bit about court affairs.
Yet precisely because he knew, the current political situation baffled him more than anything.
When he had left for the campaign, His Majesty had showered the Prince of Jin with favor and affection. Rumors in the streets had even suggested that the Zhao dynasty might truly pass from brother to brother.
But after Cao Bin departed, events in Kaifeng changed so rapidly that he could barely keep up.
In the tenth month he had written to the Emperor announcing the successful crossing of the Yangtze and boasting that within a year he would deliver Li Yu bound in chains.
The Emperor's reply had lavishly praised the crossing at Caishiji. Then, almost as an afterthought at the end of the letter, came one simple line:
"The Prince of Jin suddenly suffered madness and attempted to assassinate me. Do not worry, Guohua. The war comes first."
One short sentence.
Cao Bin had read it more than ten times, still unable to believe that the Prince of Jin had fallen from favor so abruptly. The news felt unreal.
As the campaign progressed and victories piled up, by the time he had surrounded Jiangning in the first month of the year, he had finally managed to accept it.
Then came another letter.
The Emperor informed him that the Prince of Jin, filled with remorse after the failed assassination, had chosen to renounce his title, enter the monastery at Xiangguo Temple, and take the dharma name Kongjiong.
That revelation had shaken Cao Bin all over again.
And because of that, the order appointing Zhao Dezhao to oversee the Ministry of Works suddenly looked very significant in his eyes.
Everyone knew the Emperor's eldest son had died young. Though Zhao Dezhao was nominally the second son, he was in truth the eldest legitimate heir. Now that the Prince of Jin had become Monk Kongjiong, who else could possibly contend for succession?
Under normal circumstances, Cao Bin would have responded to this messenger with strict military authority, perhaps even setting a deadline and threatening punishment if Jiangning could not be taken in time.
But considering the man's identity as an envoy from the Ministry of Works, he hesitated.
Unexpectedly, the envoy seemed to read his thoughts and immediately thumped his chest in assurance.
"Before I departed, His Highness already declared that we would take thirty days as the deadline and submit a formal pledge!"
That only made Cao Bin laugh awkwardly, repeatedly insisting that Southern Tang's defeat was already certain and there was no need for such oaths.
While they exchanged courtesies, their steps never slowed.
When they reached the riverbank, Cao Bin finally saw the so called miracle weapon.
Its components were stacked neatly aboard several boats. Judging from the banners, Cao Bin guessed they had come straight from Kaifeng at full speed.
In truth, this was also why he felt so confident in the siege.
Since surrounding Jiangning, ships from Kaifeng had sailed through the Bian Canal into the Huai River, then through the Han Canal into the Yangtze, linking north and south without obstruction.
Grain and supplies from the capital could flow here endlessly by water.
With logistics secure, besieging a single isolated city was practically effortless.
After verifying the official seals, Cao Bin boarded the ship.
Unfortunately, he knew little about engineering. Staring at the parts only made his head ache.
"General, instead of wasting effort here, you should order the imperial troops to gather stone shot or fire clay projectiles."
The voice came suddenly.
Cao Bin turned to see a man whose face again resembled that of a weathered farmer.
"Are you Master Yu?"
He knew the chief craftsman accompanying the Ministry envoy was named Yu Hao.
Yu Hao waved his hand impatiently, clearly uninterested in formalities.
"The principle of this device is simple. But if you wish to rely on it to break a city, you must prepare heavy counterweights and plenty of ammunition. Stone or clay balls will both do."
"If the General wants to understand how it works, just wait until the projectiles are ready and the engines fire together. The answer will be obvious."
"The sooner the ammunition is ready, the sooner Jiangning falls. And the sooner the General earns his merit."
Seeing Yu Hao speak with such seriousness, Cao Bin's last doubts vanished.
He had always been decisive by nature. Once he made up his mind, he quickly questioned Yu Hao about the required size and weight of counterweights and projectiles, then hurried off to issue orders.
If given the choice between returning to the capital in a month with victory or spending a year starving Jiangning into submission, the decision was obvious.
Outside the walls, the Song army remained calm.
Inside the walls, the Southern Tang troops had long since lost any desire to fight.
Sortie was impossible. They could not win in the field, and the Song army could not break in. All they could do was rely on Jiangning's towering walls.
Still, over the past two days, the defenders noticed unusual activity in the Song camp.
Sharp eyed soldiers could see several large pits being dug, as if furnaces were being built to fire something. A conscientious guard reported it to his superior, only to receive a dismissive reply:
"The Song have no siege ladders and no siege towers. How do they expect to attack?"
Two more days passed.
Now several structures resembling traction catapults rose in the Song camp. Another soldier reported again. This time he finally persuaded his officer to climb the wall and look.
The officer, said to descend from a prestigious family dating back to the Jin dynasty, glanced once and snorted.
"What use are catapults? Jiangning's walls are high. Even if a few stones reach us…"
He never finished the sentence.
The wall beneath their feet trembled.
Soldiers along the parapet saw it clearly. Several projectiles the size of millstones arced into the sky from the Song camp and slammed heavily into the city wall with deep, thunderous impacts.
The noble-born officer fell silent at once.
Then he spun and ran down the wall, screaming in a shrill voice,
"Hold the walls! Any who flee will be executed! I go to summon reinforcements!"
Below, Cao Bin saw everything clearly.
One of the stones flew slightly higher than the rest and smashed a gap into the battlements.
He burst into laughter.
"Send orders to the rear ranks. Fire more clay shot. Make plenty with sharp edges!"
"Capturing Li Yu alive may not even take a month!"