Chapter 447: High Peaks on the Liupan Mountains

"The mountains are high and long, stretching north to the desert, south to the Jing and Wei rivers. Of the four fortresses guarding the Guanzhong plain, this is the western barrier."

This was Diwu Lun's assessment after gazing up at the mountain range from the eastern foothills.

He said attacking the Long Slope was an "uphill assault" — and he meant that literally, because the terrain around Chencang is flat and low, but as you travel northwest it rises steadily, and when you reach the foot of the Long Slope, the mountain range before you suddenly soars upward!

"The slope twists back on itself nine times; none can tell how high it is. Those who wish to ascend require seven days just to cross."

The meaning is: all anyone knows is that it is so precipitous that merely crossing to the far foothills takes seven days — as for how high it is, only Heaven knows.

But today, when Diwu Lun arrived here with the army, he was determined to measure this height that "none can tell."

Du Shi, the Commandant of Waters and Forests, who had a keen sensitivity for numbers and instruments, had been transferred to the western front. Together with Ren Guang in Chang'an, one in the west and one in the east, they coordinated waterborne transport and supply matters. When Diwu Lun asked him whether there was a way to measure the height of Mount Long, Du Shi replied, "Your servant can only use the method of the tilted set-square to gaze at heights and make a rough calculation."

Diwu Lun had him demonstrate on the spot. Du Shi's tilted set-square method relied purely on experience, and the answer he produced was certainly far from the actual figure — one could only say, "Perhaps around eight hundred paces or so."

Diwu Lun was still not satisfied. He merely smiled and said, "I, on the other hand, have two methods that can measure the height of the Long Slope!"

One method used repeated measurements carried forward step by step, making it possible to measure the distances and height differences between each point, yielding a conclusion of one thousand and ninety paces.

The second method: Diwu Lun ordered the Forge Battalion to bring over the "sighting instrument" used on the great yellow crossbows for measuring the distance and height of targets.

This so-called sighting instrument was actually three horizontal lines and three vertical lines set within a frame. A scaled-down version was mounted on the sighting bar of the great yellow crossbow, allowing the shooter to use the cross-shaped grid to aim at targets up, down, left, and right. This device could also employ similar triangles to measure the height of a mountain. After repeated calculations using the mathematicians' method of the base and the perpendicular, it likewise yielded over a thousand paces.

Du Shi was deeply shaken. He spent a long time pointing the sighting instrument at flagpoles and other objects, comparing and gesturing — the accuracy was indeed very high. With the Privy Treasury in full-scale production, turning every one of Emperor Wude's ideas into reality, the small instruments and devices in the army had grown more and more numerous lately — though most, once made and tested, proved to be of little use.

This measurement was certainly more precise than guessing from experience. One thousand paces — that was the height difference between their camp at the foot of the mountain, where Diwu Lun and the others were, and the Long Slope pass in the distance.

To rise from the plains to a height of a thousand meters within a mere few dozen li — in the age of cold steel, how terrifying was that?

Diwu Lun also recalled that "Song of the Long Headwaters": "No wonder the corvée laborers from Guanzhong, conscripted to serve in Longyou, wept as they walked this mountain — only to be mocked by the men of Longyou in turn."

If it is like this in ordinary times, how much harder in times of war, when a military force from Guanzhong seeks to charge upward? The enormous gradient and the treacherous road not only test the stamina of men and horses to the utmost, but supply transport is also a formidable problem.

Could one take a detour, then? Regrettably, difficult as the Long Pass road is, it is still the "smooth path" for crossing the Long Pass.

What is more troublesome is that in the historical record, very few powers have left accounts of warfare here. When the Qin people crossed Mount Long eastward, they met little obstruction from the Rong tribes. And in the early Han, after the Han army secretly crossed Chencang, they reached Longyou with great ease — at that time Longyou was ruled by Zhang Han, and the Qin people loathed this man who had caused two hundred thousand of their sons and brothers to be massacred by the Chu army. They were, on the contrary, quite welcoming toward the Han army with its "three-article covenant," so the region essentially submitted as soon as the proclamation arrived.

Thus Diwu Lun had no battle precedents to consult. He could only let his officers and commanders feel their way forward step by step.

"For the main army to attack the Long Slope, we should use the Guanshan grasslands halfway up the mountain as our forward camp."

This proposal came from Wan Xiu. The Guanshan grasslands lie in the middle section of Mount Long's eastern foothills. It is said that this was where Feizi, the ancestor of the Qin people, pastured horses for the Zhou king. There are broad stretches of level ground where one can pitch camp and station over ten thousand men. In the height of summer, the grasslands are lush, which can also ease the pressure of foraging for the livestock.

But advancing further upward would not be so easy. The Long Pass road becomes extremely narrow and winding, forcing one to inch upward along switchback mountain paths. And at the end of the mountain road lies the precipitous Long Slope, where the Long army is already waiting at ease to strike hard at any Wei army attempting an uphill assault on the pass.

The vanguard spent three days just on the march. On the fourth day they launched a probing attack, and the result was deeply disheartening: even the ever-fierce Imperial Guard Division was driven off the mountain.

Merely watching the battle from the Guanshan grasslands, Diwu Lun could feel the grueling difficulty of the fight. He could only sigh and say, "Now I understand what Wang Chang of the Greenwood felt when he faced the Tong Plateau."

The Long Slope is even more treacherous than the Tong Plateau. No matter whether the Wei army has thirty thousand, fifty thousand, or even a hundred thousand men east of Mount Long, on the narrow, elongated Long road, the advantage of numbers is nullified. Large-scale siege engines absolutely cannot be hauled up, and there is no place on Guanshan even to set up small catapults.

By the third day of the sustained offensive, even though Diwu Lun had set a heavy bounty in gold for the first to ascend, yet another brigade was defeated and driven back by a counterattack from the sons of good families and the bonded retainers of Longyou.

Dragging this out in a prolonged standoff would have no end, because the western foothills of Mount Long are gentler, making support and resupply more convenient for the Long army than for the Wei army.

This was also why Diwu Lun had to divide his forces in this campaign: rather than cramming over a hundred thousand men at the foot of the mountain and worsening the supply burden, it was better to let the brothers go up the mountain and each strive on his own!

With the fighting having reached this point, Diwu Lun was now clear on just how hard it was to break through the Long Pass by brute frontal assault. He began ordering the troops to withdraw in stages back to the foot of the mountain, leaving a few thousand men on the Guanshan grasslands to make a show of force and maintain pressure.

So now they could only wait for good news from Young Geng and Wu Han's combined operation on the Xiao Pass road? But it was hardly that easy. Wu Han had been maneuvered by Diwu Lun — using a brevet general's title and a marquisate, old Wu had been lured from Youzhou to Guanzhong, while the Youzhou shock cavalry under his command was taken over by Jing Dan. In this way, the newly joined "Youzhou faction" was placed firmly in the hands of Diwu Lun's own trusted confidants — he would have to be mad to transfer the utterly undisciplined Yuyang shock cavalry to Guanzhong to wreak havoc on the countryside.

So although Wu Han's "Independent Division" kept its unit designation, its men had been completely replaced. It was currently at the stage where the general did not know his soldiers and the soldiers did not know their general. Striking west from Beidi, the road was still full of hardship and peril, and the cities had to be taken one by one.

As for Geng Bozhao's Bingzhou shock cavalry, originally counted on to deliver a swift, fierce blow to the back of Longyou, the Xiongnu had suddenly increased their tribal presence along the Helan Mountains, forcing them to leave men behind to guard Fuping and preventing them from all moving south. Their progress would likely be delayed as well.

"Fighting in Longyou is a matter of wearing down one's temperament — there's no rushing it."

Though he said this, Diwu Lun had no wish to wait idly. He thought to himself, "It seems this 'lower-route army line' must be set in motion after all!"

…

"This route through the Wei River defile was not in my original plans. It was entirely Lord Junyou's idea, and Lord Junyou has said several times that preparations are complete and several thousand troops can be sent west at any time."

When Diwu Lun returned from the Guanshan grasslands to Chencang, he discussed it again with Wan Xiu: "But when I asked around in Chencang, everyone said the defile is no path for men."

At the southern end of Mount Long, the Wei River has forcibly carved out a long, narrow, deep trench. By all logic, in most places, following a river valley always allows one to open up a road — such as the Baoye Road through the Qinling Mountains, which relies entirely on the Bao and Ye rivers. But the Wei River happens to be an exception. In many places there are high mountains and sheer cliffs. To follow the Wei River through Mount Long, apart from building plank roads, there is virtually no other way. Yet no previous dynasty ever undertook such a project, and the swift, turbulent current also means that rowing upstream is impossible.

"Though the Wei River defile is treacherous, it is not impassable to men."

"The reason I dare say this is because I personally led troops, disguised as woodcutters, and scouted westward along the Wei River."

Wan Xiu had not been idle during his year and a half guarding the Right Fufeng. Although his health had declined as he entered middle age, he still often went to the front lines in person.

He pointed out on the map for Diwu Lun this route, which had cost no small number of lives to reconnoiter: "This road goes west from Chencang, crosses a ford, and follows a treacherous path carved through mountain gorges. It weaves back and forth several times among the ridges and rivers, passes Maiji Mountain, and after a journey of several hundred li, ultimately reaches Shanggui in Longxi — present-day Qinzhou District in Tianshui!"

Wan Xiu strongly advocated this plan: "Although it is mainly suited for local villagers coming and going, and unfavorable for large formations of troops marching through, there is no shortage of water sources. One can also dispatch a surprise force, carrying parched flour as dry rations."

He began to volunteer: "Let Your Majesty hold the line at Chencang. Your servant is willing to personally lead a flanking force to strike! In no more than half a month, we can stab into the heart of Longyou!"

Diwu Lun found this remarkable: "If Geng Bozhao, Wu Han, or even Wenyuan had made such a proposal, I would not find it strange."

"But Lord Junyou has always presented himself as a Confucian knight and gentleman, and his use of troops is as steady as Jingsun's. Why such keen aggressiveness this time?"

Wan Xiu replied, somewhat sheepishly, "Though I took to book-reading in my later years, in my youth, I too was a knight-errant of the Five Tombs, living by swift pleasures and swift vengeance!"

"Now that the Long Slope proves so hard to cross, how could I begrudge my own humble body and shrink from marching into the army's hardship and peril?"

"A fine general!" Diwu Lun still hesitated somewhat. The reason he had been holding this line of advance in check was that the Wei River defile, like the Ziwu Valley, seemed a "cunning stratagem" but was in fact far from a foolproof plan.

He then said, "Longyou will certainly seek aid from Gongsun Shu. I have left Cen Peng to guard Weinan and the Ziwu Valley. If the Shu army dares to risk the danger, I shall ensure they come but do not return."

"The Wei River defile is the same. Do you think Longyou lacks men of good judgment? If someone with insight advises them and they send troops to intercept and ambush you in the remote fastnesses of Maiji Mountain, you will be isolated and without support, unable to advance or retreat. Not only will five thousand men be lost, but our army's morale will be gravely wounded."

Wan Xiu, however, was unwilling to remain forever in the role of a rearguard anchor. He again petitioned, "Given the situation in Longyou, if a surprise force can penetrate into its heartland, the powerful families of Longxi will surely be thrown into great alarm and will grow alienated and disloyal. By that time, I will no longer be fighting alone!"

Wan Xiu believed that the interior of Longyou was in fact not stable. Wei Ao had taken command in the wake of defeat, and his prestige was not enough to silence the other dozen or so powerful clans — not to mention the existence of a pro-Han restoration faction centered around the child Ying.

In Wan Xiu's view, if they could fight their way into Longxi, where the Wei family could not make its word law, the powerful clans of Longyou would be profoundly shaken. They might well exercise the great clans' traditional skill: push Wei Ao forward to bear all the blame for resisting the imperial army, and sell him for a good price!

"The world says I am timid in the use of troops. This time I can justly take a slight risk, striking beyond all expectation. I shall win through the unexpected, while Your Majesty engages them with the orthodox! The Long army can be utterly routed."

Wan Xiu petitioned again and again. As the days slipped into the sixth month with no progress on either the Long Pass or Xiao Pass roads, Diwu Lun simply gazed up at the high peaks of the Liupan Mountains, where the sky was high and the clouds pale.

The climate in this region is relatively arid, and there had been no unbroken torrential rains. But if they waited much longer, that might not hold — this was indeed the most suitable opportunity to take the Wei River defile.

"Junyou." Diwu Lun finally relented. "You are not only my strong bow. When we were in the New Qin Heartland, you shot down the south-flying wild goose for me to use as a betrothal gift — that is why I regard you as family."

Diwu Lun had a Palace Gentleman bring a battle-axe specifically used for conferring the rank of general. He held the axe-head himself and handed the haft to Wan Xiu — a mark of the utmost trust, for if the general harbored treachery, he could take it and even cut down the Emperor.

"General, you too shall be my sharp axe."

Diwu Lun granted Wan Xiu's request for battle, speaking with emotion — and in the process, without realizing it, he stole yet another idiom that rightfully belonged to Xiu'er.

"And for me, hew through brambles and thorns!"