His mission was to lead 30,000 troops to block the Shu general Jiang Wei at a bridge in Yinping (陰平) and stop him from reinforcing Yang'an Pass (陽安關).
When Jiang Wei heard about it, he pretended to launch an attack on Yong Province via Konghan Valley (孔函谷).
Zhuge Xu fell for the ruse, thought that Jiang Wei wanted to attack his base, so he ordered his troops to retreat from Yinping by 30 li.
Later, the Wei general Zhong Hui advanced south from Yang'an Pass and reached Baishui (白水).
At Baishui, Zhong Hui accused Zhuge Xu of cowardice, seized command of his troops and sent him as a prisoner back to Yong Province.