Guo Huai then ordered Chen Tai, Xu Zhi and Deng Ai to lead Wei forces to attack the fortresses at Qushan and cut off their food and water supplies. Ju An and Li Xin led their men to taunt Deng Ai to attack them, but Deng Ai ignored them. As time passed, the two fortresses gradually ran out of supplies. Jiang Wei led his troops from Mount Niutou (牛頭山; west of present-day Zhaohua District, Guangyuan, Sichuan) to reinforce the fortresses. They encountered Chen Tai and his troops along the way. Chen Tai said: ""The Art of War" says that the best way to win a battle is to win without fighting. If we manage to occupy Mount Niutou, Jiang Wei's return route will be sealed off and he can be easily captured by us." He then ordered his troops to build forts to resist Jiang Wei's forces but refrain from engaging the enemy. At the same time, he also wrote to Guo Huai and requested his help in attacking Mount Niutou. Guo Huai did so and led his troops across the Tao River in preparation for attacking Mount Niutou.