Battle of Mount Qi

The Battle of Mount Qi refers to a military conflict which happened around Mount Qi between the states of Cao Wei and Shu Han in 231 AD during the Three Kingdoms period of Chinese history. It is also the most vigorous campaign of the five expeditions Shu launched against Wei, resulting in thousands of death on both sides. After this campaign ended with Wei as the victor, Shu regent, Zhuge Liang, spent 3 years to recuperate before he launched a final assault on Wei in 234 AD.

Background
In 217 AD, Liu Bei's strategist, Fa Zheng, proposed that Hanzhong could be used as an operational base to either attack the heartland of Cao Wei or ingest the far-left-hook of Wei's Liang and Yong Provinces. Since then, Fa Zheng's plan became a blueprint for Zhuge Liang's expedition against Wei. Zhuge Liang had attempted to invade the northwestern lands via Mount Qi in his first expedition but to no avail; he then changed target to Chenchang, a bridgehead fortress guarding the metropolis city of Chang'an. However, staunch defense of the fortress proved to be formidable, swinging Zhuge Liang back to the western attack route. In early 231, Zhuge assembled a force to conqure Longyou, setting Mount Qi as his immediate target. Before Zhuge Liang marched towards Mount Qi, he had envoys sent to rouse the Xianbei and Qiang people, urging them to create a disturbance in the Wei rear, and had invented and produced the "wooden ox", which was said to have had greatly improved the logistics.

Battle
Nevertheless, the goal of seizing Longyou was not an easy target, because Wei's defensive posture in the region was gestured for a probably Shu Han invasion - Mount Qi was garrisoned by Jia Ji and Wei Ping, forming an initial defense for Tianshui commandery, while Dai Ling (戴陵) and Fei Yao stationed their crack troops at the heartland of Tianshui. Despite the Xianbei leader, Kebineng, had arrived Fuping County to echo the Shu forces, the offensive began with a minor clash at Mount Qi, giving the Wei commander-in-chief, Cao Zhen, an impression that the attack was a diversion to mask a major offensive through the Qinling passes against the prosperous Chang'an. Therefore, the stricken Cao Zhen gathered the majority of the defense forces inside Chang'an before he was absolved and replaced by Sima Yi. The new commander then ordered Dai Ling and Fei Yao to protect Shanggui with 4,000 elite troops and set out with the rest of his men westward to relieve the mountainous battlefield. Zhang He, an veteran general whose military experience towered above that of Sima's, challenged the marshal by claiming the army should be split to also protect the districts of Yong and Mei, but Sima Yi disagreed, saying the vanguard alone could not resist the enemy.

On hearing of Sima Yi's advance, Zhuge Liang left part of his army besieging Mount Qi and set out with the remainder to seize Shanggui. Without good coordination, the eager vanguard of Wei defied Sima's simple order to defend–a detachment left the defensive position and stroke the newly arrived Zhuge Liang, but the squad was instead badly defeated. After ridding of the nuisance, Zhuge Liang foraged for the early spring wheat that was available in the vicinity. Sima Yi, after surveying the situation at Mount Qi and Guo Huai's defeat, decided to reinforce the loser and speedily marched to the wheat-field. The two armies met at the east of Shanggui, each held firmly a strategic location and refused to give battle sloppily. Originally, Wei emperor, Cao Rui, wanted to supply Sima's army with the wheat in Shanggui, and turned down the proposal to transport grain from Guanzhong; however, Zhuge Liang's movement was quicker than the young leader anticipated, and only a portion of the wheat produce was retained. To supply the defensive forces, Wei's Yong Province Governor, Guo Huai, asserted his influence upon local nomadic tribes and received plenty of food from them. Thus, the Wei army was able to supply itself without the aid from central government.

Upon completing the harvest the Shu forces retreated, but they were trailed and caught up by Sima Yi at Hanyang (漢陽), where the follower sent out his general, Niu Jin, to noose Shu forces into a trap the hunter meticulously prepared. However, after the Shu vanguard, Ma Dai, had briefly fought Niu Jin, Zhuge Liang signaled a general retreat toward the eastern end of Qishan ridges, sojourning Shu army at Lucheng (鹵城, Lu Fortress), an ideal site for a showdown. There, the Shu-Han Chancellor sent his generals to station on two mountains north and south to the lone fortress, and had soldiers pitched "covering camps" near the riverbanks to take complete rein of the water route. Generals under Sima Yi urged the latter to attack on numerous occasions, but the careworn marshal was hesitant to do so upon seeing his arch-rival's arrangement. Nevertheless, faced with intensive criticism and ridicule from both enemy and subordinates, a disgraced Sima Yi eventually relented. In May, Sima Yi sent an earnest Zhang He to attack Shu southern camp guarded by Wang Ping, while he personally led a frontal assault against Lucheng from the central avenue. Pressed by clouds of black-clad guards under the banners of Sima, Zhuge Liang ordered Wei Yan, Wu Ban, and Gao Xiang to resist the raven horde outside the city wall, where the dark knights suffered an unexpected and tremendous defeat: 3,000 elite soldiers were killed, and 5,000 suits of ebony armor and 3,100 sets of hornbeam-made crossbows were seized by Shu. Even the loss was heavy, Sima Yi still retained a sizable army, which he led back to its encampment.

After such a resplendent victory, however, Zhuge Liang could not capitalize on it with a major offensive due to dwindling food supply. Adverse weather prevented Shu's logistics from delivering matériel on schedule, and Li Yan, the Shu official responsible for maintaining ration supplies to the front, fabricated that the emperor Liu Shan had ordered a withdrawal. In the Book of Jin, it is claimed that Sima Yi again launched an attack on Shu garrisons at this juncture, succeeding in capturing Zhuge Liang's outer camps. The Prime Minister abandoned Lucheng and retreated under the cover of night, but was caught up by Sima Yi, who dealt Zhuge Liang a casualty of roughly 10,000.

There was a dramatic turn during Shu retreat, though. Sima Yi, letting go of his usual cautiousness after his prior success over Zhuge Liang, ordered Zhang He to further pursue the enemy in an attempt to capitalize on their momentum. Weilüe reports that Zhang He refused Sima Yi's order and argued with his superior that an army returning home should not be chased, in accordance with classical military doctrine. The Grand Marshal, however, refused to listen and forced the general to carry out his fiat. Indeed, Zhang He fell into a choreographed meat grinder laid at Mumen, where Zhuge Liang had ordered massed crossbowmen to hide at high grounds and fire at approaching enemies when the prey entered a narrow defile. Hemmed by heavy cross-fire, even Zhang He was hit by a fatal shaft on his right leg, ending the old general's long journey of military career and leaving Sima Yi being the single most valued military authority of Cao Wei.

Aftermath
When Zhuge Liang returned to Hanzhong, he received a letter from Li Yan informing him that the food supply was ready and questioning why he had retreated. At the same time, Li Yan sent Liu Shan a memo which says "the army feigned retreat in order to lure the enemy to do battle" in hope that Zhuge Liang would resume the war so his failure to transport ration would go unnoticed. However, Zhuge Liang decided to return to Chengdu and show Liu Shan the handwritten letters of Li Yan, so the latter could not deny the fault. At Shu capital, Zhuge Liang asked the emperor to strip Li Yan off all of his prestige titles and official posts and exile the guilty Li Yan to Zitong commandery.