Zhang Jue
The Jurchens, sensing Song weakness, used the Zhang Jue incident as a pretext to invade. In 1125, Jin forces defeated Guo Yaoshi at the Battle of the Bai River, on the upper reaches of the Chaobai River in modern Miyun County. Guo Yaoshi then surrendered Yanshan and then guided the Jin's rapid advance on the Song capital, Kaifeng, where the Song Emperor was captured in 1127, ending the Northern Song dynasty. Yanshan was renamed Yanjing.