In spring 384, Murong Chui openly declared the establishment of Later Yan, claiming the title of Prince of Yan. Fu Pi tried to persuade Murong Chui to end his rebellion, but Murong Chui refused and attacked Yecheng but was unable to capture it quickly. However, most cities north of the Yellow River and east of Taihang Mountains switched allegiance or were captured by Later Yan forces, leaving Yecheng isolated. (The Former Qin cities south of the Yellow River were largely captured by Jin.) With the heart of the empire itself under attacks by rebel regimes Later Qin and Western Yan, Fu Pi could have no expectation of receiving aid, and the situation soon grew desperate for him and his troops. In late 384, Murong Chui briefly lifted the siege of Yecheng to try to regroup, but at the same time, Jin forces attacked. Fu Pi sued for peace, but without his knowledge his assistant Yang Ying (楊膺) also promised on his behalf that he would surrender to Jin. With that promise, the Jin general Xie Xuan aided him with troops and food supplies, but eventually the temporary alliance broke up again. Meanwhile, Murong Chui returned and again put the city under siege after defeating Jin troops under Liu Laozhi (劉牢之). In 385, Fu Pi abandoned Yecheng and headed northwest to Jinyang (晉陽, in modern Taiyuan, Shanxi), where he received news that his father Fu Jiān had been killed by the Later Qin ruler Yao Chang. He then declared himself emperor.