Northern Expeditions

The Fourth Northern Expedition

Zhuge Liang's fourth Northern Expedition was launched in early 231 with the same immediate goals as the third, that is, capture of the Wudu-Yinping region to serve as a forward base. Envoys were sent out to rouse the Xianbei and Qiang, urging them to create a disturbance in the Wei rear. Furthermore, supply was improved with the introduction of the 'wooden ox', an instrument invented by Zhuge that was able to successfully prevent the Wei soliders from stealing their supplies as the Wei soliders couldn't make these oxes move. Nevertheless, the goal of seizing Longyou was perhaps overly optimistic since Wei's defensive posture in the region was indeed formidable. Qishan was garrisoned, forming an initial defense for Tianshui, which was itself occupied by the battle-tested forces of Guo Huai and Dai Ling. The Shu offensive began with a minor clash at Qishan which the commander-in-chief Cao Zhen feared was a diversion to mask a major offensive through the Qinling passes against Chang'an itself. In the early summer Cao Zhen took ill and was replaced by Sima Yi, who at once set out with the main army at Chang'an to relieve Qishan. On hearing of Sima's advance, Zhuge left part of his 30,000-man army besieging Qishan and set out with the remainder to seize the various Wei garrisons dispersed around Tianshui.

Without the benefit of strategic control, his opponents played into his hands. Guo Huai had been ordered to join Sima Yi at Qishan but he took the initiative and together with Fei Yao, garrison commander of Shanggui tried to catch Zhuge Liang in a front-rear pincer attack. Having left the defensive position, they were routed by the Shu forces, leaving the approaches to Longyou open. Zhuge, however, did not move to take Tianshui, perhaps fearing the breakdown of the supply line should the Shu army overextend itself. Instead he went about harvesting the early spring wheat that was available in the vicinity under the scrutiny of the enemy. Sima Yi, after surveying the situation at Qishan and Gou Huai's defeat, occupied the hills east of Shanggui, blocking any further Shu advance. Upon completing the harvest the Shu forces marched south and halted, preparing for battle; but Sima Yi declined the challenge. Faced with intensive criticism and ridicule, he relented and the ensueing frontal assault by the Wei forces was ruinously defeated. The Wei forces were forced to retreat in disorder and accounts of the battle note that the Shu forces captured 3000 sets of armour, 5000 swords, and 3100 crossbows.

After such a victory, Zhuge Liang, perplexingly, did not capitalise on it with a major offensive. Instead the Wei-Shu armies settled down to a stalemate at Shanggui of which the resource-poor Shu would surely be the loser. At this juncture, Li Yan, who was responsible for maintaining ration supplies to the front, realising rain had caused the breakdown of transport, informed Zhuge that the Shu emperor had ordered a withdrawal. How disappointing it must have been for his plans to be frustrated once again. There was, however, some consolation in the retreat. Sima Yi, letting go of his usual cautiousness, ordered Zhang He's cavalry to pursue. At Mumen, Zhang was ambushed by massed crossbowmen as his army entered a narrow defile and killed.

The Fifth Northern Expedition

In the following two years both sides developed agriculture and prepared for another inevitable campaign in Longyou. Sima Yi, for his part rehabilitated the Zheng Guo canal of 234 BC, increasing the potential to withstand a protracted war in Longyou.

Sun Quan's armies in the Huai region, however, was defeated and his offensive broke down due to the spread of endemic disease. The frustration of this last hope to break the stalemate no doubt increased the rapid deterioration of Zhuge Liang's health and depressed mental condition. By late summer, he started giving instructions to his close subordinate officers on the future of Shu. In the early autumn of 234, Zhuge Liang died at the age of 54. News of his death was withheld until the army had reached the safety of the Baoye valley to return to Hanzhong. Sima Yi, fearful that the announcement was false and merely another opportunity for Zhuge to demonstrate his talent for ambuscade, hesitated to pursue. Only after his inspection of the empty Shu encampment did he resolve that pursuit was appropriate, but after reaching Baoye and deciding the advance could not be supported with supplies, the Wei army returned to the Wei River. The death of Zhuge Liang ended a huge strategic threat to Wei and the Wei court soon began development of ambitious public works.