Yang Fugong had been instrumental in having Emperor Zhaozong made emperor, but by 889 conflicts had begun between the emperor and the chief eunuch, leading to a public argument between Yang and the chancellors Kong Wei on one occasion over Kong's accusation that Yang was disrespecting the emperor.

Nothing further had come of the dispute publicly at this point, however.

Nevertheless, at the suggestion of Kong's colleague Zhang Jun, who advocates that a strong imperial army directly under the emperor is essential for the restoration of imperial power to counteract the warlords and the eunuch-commanded Shence Armies, Emperor Zhaozong begins recruiting an imperial army that eventually numbers one hundred thousand by spring 890.

At this point, Kong and Zhang believe that it is time to test this army, to show its strengths in the struggle against Yang at court.

Zhang therefore advocates a campaign against the warlord Li Keyong the military governor of Hedong Circuit (headquartered in modern Taiyuan, Shanxi)—one of the most powerful warlords of the realm and archrival to the also powerful Zhu Quanzhong—as both Zhu and Li Kuangwei the military governor of Lulong are at this time also requesting an imperial campaign against the expanding Li Keyong.

Emperor Zhaozong, despite his reservations, approves the campaign, which gets under way in summer 890, with Zhu's army attacking Zhaoyi Circuit (headquartered in modern Changzhi, Shanxi), then also under Li Keyong's control, from the southeast; Li Kuangwei and Helian Duo the military governor of Datong Circuit (headquartered in modern Datong, Shanxi) attacking from the northeast; and the main imperial army, under Zhang's command and supplemented by the armies of various circuits around Chang'an, attacking from the southwest.

Zhu's army was able to seize Zhaoyi quickly, due to the assassination of Zhaoyi's military governor Li Kegong (Li Keyong's brother) by his officer An Jushou, but the imperial official sent to take over Zhaoyi, Sun Kui, is intercepted and captured by Li Keyong's adoptive son Li Cunxiao (and subsequently executed when he will not submit to Li Keyong), badly affecting the imperial army's morale.

Li Cunxiao subsequently puts Zhaoyi's capital Lu Prefecture under siege, forcing Zhu's army to withdraw.

Li Kuangwei and Helian's armies are also repelled by Li Keyong's adoptive sons Li Cunxin and Li Siyuan, leaving Zhang's imperial army to face Li Keyong himself.

By late 890, the imperial army is suffering repeated defeats at the hands of Li Keyong's Hedong army, and the supplemental troops from Jingnan (headquartered in modern Xianyang, Shaanxi) and Fengxiang (headquartered in modern Baoji, Shaanxi) Circuits abandon the imperial army and withdraw by themselves, eventually leading to a total collapse of the imperial army, with Zhang and his deputy, Han Jian the military governor of Zhenguo Circuit (headquartered in modern Weinan, Shaanxi) escaping with just a small contingent; the rest of the imperial army is effectively lost.

With Li Keyong subsequently threatening an invasion, Emperor Zhaozong is forced to restore Li Keyong to his titles and positions and exile Zhang and Kong, ending the campaign against Li Keyong in disaster.