During the Khitan invasion of 696-697, Yao Chong was serving at the ministry of defense, when there was much emergency paperwork due to the Khitan invasion. Yao conducted the official business with efficiency and gave much useful comments when he processed the paperwork. This impressed Emperor Gaozong's wife Wu Zetian, then "emperor" (the only woman with that title in Chinese history) of her Zhou Dynasty, and she gave him an unusually steep promotion to be the deputy minister of defense (夏官侍郎, "Xiaguan Shilang").