Meng Da’s rebellion and defeat is a failed attempt to turn Wei’s frontier commanders and territories against their ruler. It briefly appears to open a route for Shu toward Chang’an and even Luoyang, but Sima Yi’s rapid, independently chosen response overturns those hopes. The episode makes time, trust, and the position of a city’s gates decisive: Meng Da waits for allies who have already deceived him, while Sima Yi moves before he has been formally ordered to act and uses a false message to keep his opponent off guard.

A Rebellion and a Strategic Opening

At Qishan, Kong Ming receives news that Meng Da, who had surrendered to Wei, intends to change sides again. Meng Da plans to seize Jincheng, Xincheng, and Shangyong, then march on Luoyang. At the same time, Kong Ming is preparing to move toward Chang’an. The two developments seem capable of combining into a major advance: Shu might threaten both of Wei’s ancient capitals from different directions.

That prospect changes when Kong Ming learns that Sima Yi has been restored to command and given responsibility for Wei’s army. Kong Ming immediately recognizes the danger. In his assessment, Sima Yi is too formidable to leave Meng Da time to organize: if Sima Yi takes the field against him, Meng Da is likely to lose. Kong Ming sends a warning urging Meng Da to strengthen his defenses against a surprise attack. The warning is sound, but it arrives at a moment when Meng Da believes he can afford to wait.

A Race Against the Warning

Meng Da dismisses Kong Ming’s concern. He replies that Sima Yi is far away and that he has at least a month in which to repair the city’s defenses. Kong Ming predicts that this estimate will prove fatal. He invokes the principle of striking before an enemy is ready, reasoning that Sima Yi will not wait for permission and can reach Meng Da within ten days. The episode thus places strategic knowledge and its practical use in sharp contrast: Kong Ming accurately assesses the speed of Sima Yi’s response, but Meng Da does not act on the intelligence he receives.

Sima Yi in fact does not proceed to Chang’an as instructed. He sees that Meng Da’s rebellion can be neutralized by a swift march and sets out without waiting for orders. On the way, he joins forces with his former fighting companion Xu Huang. When Sima Yi learns that Kong Ming has warned Meng Da about a possible surprise attack, he acknowledges Kong Ming’s judgment and presses his men to move faster. The competing commanders understand the same danger, but Sima Yi converts that understanding into immediate action.

The False Message and the Collapse

Meng Da’s plans depend not only on his own troops but also on governors in Jincheng and Shangyong, whom he expects to join the revolt. They delay sending their forces, claiming they need more time to prepare. Their apparent hesitation helps preserve Meng Da’s expectation of support, even as it leaves him without the reinforcement he needs.

Sima Yi exploits that confidence with a false message. He writes to Meng Da as though Meng Da remains a loyal Wei commander, telling him to prepare to march to Chang’an. When Meng Da asks where Sima Yi is, he is told that Sima Yi is already on the road to Chang’an. Believing the route to be clear, Meng Da gives orders to advance on Luoyang. The report that follows reverses his confidence: a large army is approaching his city, and Xu Huang arrives at its gate demanding that it be opened.

Meng Da responds by firing an arrow that strikes Xu Huang in the head. Xu Huang dies later that night, a significant loss even as Sima Yi’s army closes around the city. The next day, Meng Da sees two columns of troops approaching and assumes they are the forces from Jincheng and Shangyong. They have instead betrayed him. When he rides out to meet them, the revolt collapses into defeat; Meng Da is killed, and Sima Yi enters the city as a victor.

Consequences and Narrative Significance

The rebellion’s defeat removes a potential ally and territorial opening for Shu at precisely the moment when Kong Ming is considering an advance toward Chang’an. Its failure follows from several linked misjudgments and reversals: Meng Da discounts a timely warning, overestimates how long Sima Yi will take to respond, and trusts neighboring governors whose delay conceals their change of allegiance. Sima Yi, by contrast, takes the initiative without waiting for formal permission and uses a carefully misleading communication to encourage Meng Da to act before he realizes the danger.

Sima Yi then proceeds to Chang’an and presents himself to Cao Rui. The Wei ruler apologizes for having listened to bad advice and demoted him, and commends him for eliminating Meng Da’s threat. The episode therefore restores Sima Yi’s standing as well as strengthening Wei’s position. Its final turn is toward the next campaign: Sima Yi asks that Zhang He serve as his vanguard commander, the request is approved, and the two depart to confront Kong Ming. Meng Da’s defeat is not an isolated settlement but the event that returns Sima Yi to the center of the struggle against Shu.