and he put Zhang in overall command of the operations, assisted by the official Sun Kui (). As Zhang was leaving, he privately stated to Emperor Zhaozong, "Let me first eliminate the external threat for Your Imperial Majesty, and then eliminate the internal threat." These words nevertheless became known to Yang, who became apprehensive of Zhang. Further, when Yang held a feast for Zhang to send him off, Zhang refused to drink when Yang offered wine. Yang sarcastically stated, "Lord Chancellor, you are holding the imperial sword. Why are you so hesitant?" Zhang responded, "Let me first destroy the bandits, and they you will see why I am hesitant." This aggravated Yang further, and he thereafter tried to hinder the campaign. Initially, the imperial government appeared to have the upper hand, as Zhang's imperial army was supplemented by armies sent by Zhenguo (鎮國, headquartered in modern Weinan, Shaanxi), Jingnan (靜難, headquartered in modern Xianyang, Shaanxi), Fengxiang (鳳翔, headquartered in modern Baojing, Shaanxi), Baoda (保大, headquartered in modern Yan'an, Shaanxi), and Dingnan (定難, headquartered in modern Yulin, Shaanxi) Circuits, including Zhenguo's military governor Han Jian. Zhu was also attacking Li Keyong's domain from the southeast, and Helian and Li Kuangwei from the northeast. Further, just as Zhang's army was launched, Li Keyong's brother Li Kegong () the military governor of Zhaoyi Circuit (昭義, headquartered in modern Changzhi, Shanxi), was assassinated by his own officer An Jushou (), who in turn was killed by another officer, Feng Ba (), who surrendered the circuit capital Lu Prefecture () to Zhu Quanzhong's officer Zhu Chongjie (). Hearing the news, Emperor Zhaozong and Zhang, not wanting Zhaoyi to fall into Zhu Quanzhong's hands, commissioned Sun as the military governor of Zhaoyi and ordered him to report to Zhaoyi immediately. As Sun was advancing to Lu Prefecture, however, he took few precautions against a surprise attack. Li Keyong's adoptive son Li Cunxiao made a surprise attack on Sun's procession, capturing him. (When Sun subsequently would not submit to Li Keyong, Li Keyong killed him.) This demoralized the imperial army, and subsequently, with Li Cunxiao putting Lu Prefecture under siege, the Xuanwu forces withdrew from Zhaoyi. Meanwhile, Li Keyong's other adoptive sons Li Cunxin and Li Siyuan defeated Li Kuangwei and Helian, forcing them to withdraw as well, leaving Zhang's forces alone against Li Keyong himself. The imperial forces engaged Li Keyong's at Fen Prefecture (汾州, in