Fei Ying's backer is the forty-nine Mongolian flags. They don't belong to the Eight Banners Army system, but when the Qing emperor needs them, he can give them money to fight. At the same time, the Qing dynasty also needed to maintain good relations with Mongolia, because Mongolia was located on the border. If they want to launch a rebellion, or if someone launches a rebellion on the border, the Mongolian tribe will ignore it, which is a very headache for the Qing emperor.