Before 1626, the Imperial Ming army had been very badly defeated by the Manchus. Part of the Imperial Ming army's new strategy of defense after defeat was to develop Ningyuan into a military stronghold. Yuan Chonghuan, with the support of Sun Chengzong, was seriously strengthening the defense of Ningyuan in anticipation of a Manchu attack. In 1626 Kundulun Khan Nurhaci, seeing all Ming forces leaving, decided to advance towards Ningyuan, personally leading a force of 100,000-130,000 (At least 60,000) (Nurhaci boasted an unrealistic 200,000).