Zhuge Liang's Northern Expeditions - Fourth Expedition

Fourth Expedition

Zhuge Liang's fourth Northern Expedition was launched in early 231. Envoys were sent out to rouse the Xianbei and Qiang people, urging them to create a disturbance within Wei's domain. In early summer Cao Zhen took ill and was replaced by Sima Yi, who at once ordered Dai Ling and Fei Yao to protect Shanggui with 4,000 troops, and set out with the main army at Chang'an to relieve Mount Qi. In response to Sima Yi's advance, Zhuge Liang left part of his army besieging Mount Qi and rushed to Shanggui before his nemesis could arrive.

Without a coordinated strategic effort, Zhuge's opponents played into his hands. Guo Huai had been ordered to join Sima Yi at Mount Qi but he took the initiative and together with Fei Yao, tried to catch Zhuge Liang in a front-rear pincer attack. Having left the defensive position, they were routed by the Shu forces. The Shu regent then went about harvesting the early spring wheat in the vicinity. Receiving the news Guo Huai was defeated, Sima Yi altered his destination and went to reinforce the loser. The Wei marshal occupied the hills east of Shanggui, but restrained from attacking. Zhuge Liang withdrew upon completion of harvest, but was caught up by Sima Yi at Hanyang, where the latter challenged Shu forces. After the vanguards briefly engaged, however, Zhuge Liang ordered a general retreat to Lucheng (鹵城), where he could set up a better defense. The Prime Minister sent his generals to station atop two mountains both north and south to his fortress, and set up "covering camps" near the riverbanks. Generals under Sima Yi requested the marshal for a showdown, which Sima was hesitant to do so. Faced with intensive criticism and incessant ridicule, the careful marshal eventually relented. In May, Sima Yi sent Zhang He to attack the southern mountain guarded by Wang Ping, while the Wei marshal marched Lucheng from the main road. Zhuge Liang ordered Wei Yan, Wu Ban, and Gao Xiang to stop Sima Yi outside the city wall, where the two forces clashed. Sima Yi suffered a heavy defeat and Zhang He could make no progress. Nevertheless, Sima Yi still possessed of a sizable army after such a defeat, and he would continue the war.

After the victory, Zhuge Liang did not capitalize with a major offensive due to a lack of food supply, while Sima Yi, having good rejuvenation, again mounted attacks on Shu, and conquered Zhuge Liang's outer camps. Losing the camps, Zhuge Liang retreated under the cover of night, but was caught up and dealt a serious blow. Around this time, Li Yan, who was responsible for maintaining ration supplies to the front, realizing rain had caused the breakdown of transport, lied to Zhuge Liang that Liu Shan had ordered a withdrawal.

Sima Yi, letting go of his usual cautiousness after his prior success, ordered Zhang He's cavalry to further pursue the enemy in an attempt to capitalize on their recent victory. Zhang He argued with his superior that additional risks should not be taken when they had already won, but Sima threw out his title on Zhang and forced the latter to carry out his will. Indeed, Zhang He was ambushed at Mumen, where Zhuge Liang ordered massed crossbowmen to hide at high grounds and fire at the approaching enemies when they entered a narrow defile. Zhang He was hit by a stray arrow on his right leg and died, and Sima Yi became the single most valued military authority of Cao Wei.