On 8 January 756, An Lushan crossed the Yellow River, quickly capturing Chenliu (陳留, roughly modern Kaifeng, Henan) and Yingyang (滎陽, roughly modern Zhengzhou, Henan) Commanderies. He approached Luoyang, where he encountered an ill-prepared army commanded by Feng, defeating Feng quickly and forcing Feng to flee and concede Luoyang to him. Feng joined forces with Gao and urged a retreat to Tong Pass; Gao agreed, and they took up defensive positions there, and An did not proceed quickly, but remained at Luoyang, planning to declare himself emperor there. (Soon, due to accusations of the eunuch Bian Lingcheng (), Emperor Xuanzong executed Feng and Gao, and replaced Gao with Geshu Han.) Some Tang officials north of the Yellow River resisted An Lushan under the leadership of Yan Zhenqing, the governor of Pingyuan Commandery (平原, roughly modern Dezhou, Shandong).