Yuan Chonghuan
In November 1629, the Manchu army under Hong Taiji invaded China, bypassing the heavily defended Ming fortress at Ningyuan north of the Great Wall, where Hong Taiji's father Nurhaci had been defeated three years earlier at the Battle of Ningyuan. Slipping through friendly Mongol territory, the Manchus attacked to the west through Xifengkou Pass in Hebei province, aiming towards the capital at Beijing. Yuan Chonghuan, commander of the Ningyuan garrison, sent 20,000 troops under Zu Dashou to relieve Beijing. Zu crossed the Great Wall through Shanhai Pass and marched to Beijing, defeating the Manchus outside the city walls.