Battle of Xincheng - The Rebellion

The Rebellion

There are two accounts of Meng Da's motive for rebelling, both of which are generally similar but there are some slight differences. The first account is from an annotation from the Weilue added to the biography of the Wei emperor Cao Rui in Records of the Three Kingdoms; the second account is from Sima Yi's biography in the Book of Jin.

The Weilue account mentioned that Zhuge Liang planned to induce Meng Da to defect to Shu when he heard that Meng was feeling uneasy in Xincheng. Zhuge Liang wrote several letters to Meng Da and the latter replied. Shen Yi (申儀), the Administrator of Weixing (魏興; around present-day Shiquan County in Shaanxi and Yunxi County in Hubei), who had a feud with Meng Da, secretly reported to the Wei imperial court that Meng was having dealings with Shu, but the Wei emperor Cao Rui refused to believe. Sima Yi, who was stationed at Wan at that time, sent an adviser Liang Ji (梁幾) to investigate and also urged him to travel to the capital Luoyang. Meng Da became suspicious and feared for his life, so he rebelled.

The Book of Jin account confirmed that Meng Da did have disagreements with Shen Yi. Zhuge Liang planned to make use of this incident to lure Meng Da to defect to Shu, so he sent Guo Mo (郭模) to meet Meng. However, the plot was discovered by Shen Yi. When Meng Da heard that the plot had been leaked out, he immediately made plans for a rebellion. Sima Yi, who was at Wan at that time, became worried that Meng Da would proceed with the revolt quickly, so he wrote a letter to Meng to calm him down. Meng Da was pleased when he received Sima Yi's letter, and he entered a dilemma on whether to rebel or not. During this time, Sima Yi secretly led his forces from Wan towards Xincheng. Sima Yi's subordinates suggested that they observe Meng Da's actions first before advancing, but Sima replied, "(Meng) Da is not a trustworthy person. Now that he is hesitating due to suspicions, we should seize this opportunity to get rid of him." Sima Yi's army then advanced quickly and reached Xincheng after eight days.

Shu Han and Eastern Wu also sent their forces to support Meng Da, which arrived at An Bridge (安橋) at Xicheng (西城) and Mulan Fort (木闌塞) respectively. Sima Yi despatched his subordinates to deal with Meng Da's reinforcements.

Before the battle, Meng Da wrote a letter to Zhuge Liang, agreeing to help Shu and predicting that Sima Yi would not come. However, eight days later when Sima Yi's army had arrived, Meng Da wrote to Zhuge Liang again, expressing shock and disbelief that Sima had reached Xincheng in just eight days. Meng Da was based in Shangyong (上庸), a city in Xincheng which was surrounded on three sides by water, so he set up wooden barriers to defend himself. Sima Yi's forces crossed the waters, destroyed the barriers, and arrived just outside Shangyong. Sima Yi then split up his army to attack Meng Da from eight directions. Sima Yi tempted Meng Da's nephew Deng Xian (鄧賢) and subordinate Li Fu (李輔) into surrendering, which they did so by opening Shangyong's gates after sixteen days of siege. Meng Da was captured and executed, and his head was sent to the Wei capital Luoyang.