洮河
Wang Jing, with virtually no military experience, had gravely underestimated the enemy and erroneously believed that the Shu army would be tired after the prolonged march, and it would be better not to provide them with any chance to rest and regroup, but to defeat them early in a pre-emptive strike. Wang Jing was confident that he would score a decisive victory because of his numerical superiority, and because unlike the Shu army whose supply line was overstretched, he had no such logistic problems. Therefore, Wang Jing ignored Chen Tai's order to remain in Didao, and instead led his force to Gu Pass (故關) on the upstream of the Tao River. Gu Pass is located to the north of present-day Lintao County, Gansu, and it is on the western bank of the Tao River. In October 255, both sides clashed on the western bank of the Tao River, and Wei suffered a disastrous defeat: the number of soldiers drowned in the Tao River in their attempts to escape alone totalled more than 10,000, and most of Wang Jing's troops were lost. Wang Jing was forced to lead his remaining 10,000 troops back to Didao in the south after crossing the Tao River, and regroup behind the safety of the city walls. The battle on the western bank of Tao River, known as the Battle of Gu Pass (also known as the Battle of Taoxi), was the greatest victory Jiang Wei had achieved in his northern expeditions, and it was also his last.