 As Zhili troops launched a surprise attack on May 4, the 16th Division of the Fengtian army (composed of ex-Zhili troops commanded by Feng Guozhang) defected to Wu Peifu.The Temporarily Organized 1st Division of the Fengtian army was forced to retreat from Fengtai, and its defense collapsed on the western front.It was only when the 1st Division of the Fengtian army was deployed in a counterattack that the Zhili advance was checked and Changxindian (长辛店) was retaken.