How a single tactical blunder turned a massive military victory into a strategic defeat
In 255, Shu general Jiang Wei launched a massive invasion of Cao Wei, achieving his greatest victory at the Battle of Gu Pass. Yet, by choosing to besiege the city of Didao instead of pressing his advantage, he allowed the Wei forces to regroup, ultimately forcing a humiliating retreat.
The 255 campaign was one of the largest expeditions ever assembled by Shu general Jiang Wei, involving at least 30,000 men. Jiang Wei aimed to exploit the power vacuum following the death of the Wei regent Sima Shi. His initial success was overwhelming; at the Battle of Gu Pass, he crushed the forces of the Wei Inspector of Yong Province, Wang Jing. The defeat was catastrophic for Wei, with over 10,000 soldiers drowning in the Tao River alone as they attempted to flee the carnage.
Despite this triumph, the campaign faltered due to a critical error in judgment. Against the advice of his commander Zhang Yi, who recognized the fragility of their overstretched supply lines, Jiang Wei insisted on besieging Didao. This decision provided the Wei military, led by the strategic Chen Tai, the time needed to organize a relief effort. Chen Tai correctly identified that the Shu army lacked the logistics for a prolonged siege and that the city’s defenders would fight with desperate resolve.
While other Wei commanders, including Deng Ai, initially advocated for a cautious approach, Chen Tai pushed to bypass Jiang Wei’s position and occupy the high ground southeast of Didao. By establishing a link with the besieged city through smoke and drums, Chen Tai boosted the morale of the defenders and effectively neutralized the Shu threat. Faced with dwindling supplies and a reinforced enemy, Jiang Wei was forced to abandon the siege and retreat. The battle concluded as a Wei victory, though the human cost was so severe that the emperor Cao Mao later ordered a massive effort to recover and bury the thousands of soldiers still lying in the Tao River months after the fighting ended.
Source: Battle of Didao
