Ma Su
In response to the Shu invasion, Cao Rui moved from Luoyang to Chang'an to oversee the defences and provide backup. He ordered Zhang He to attack Zhuge Liang at Mount Qi, and Cao Zhen to attack Zhao Yun and Deng Zhi at Ji Valley. Zhao Yun and Deng Zhi lost the Battle of Ji Valley because their decoy force, composed of the weaker soldiers in the Shu army, were no match for Cao Zhen and his well-trained troops. (Zhuge Liang had reserved the better troops for the attack on Mount Qi.) In the meantime, Zhuge Liang sent Ma Su to lead the vanguard force to engage Zhang He at Jieting (街亭; located east of present-day Qin'an County, Gansu). Ma Su not only disobeyed Zhuge Liang's orders, but also made the wrong moves, resulting in the Shu vanguard suffering a disastrous defeat. After his victory at the Battle of Jieting, Zhang He seized the opportunity to attack and recapture the three commanderies.