[5] As of spring 882, Zheng Changtu was serving as Zhongshu Sheren (中書舍人), a mid-level official at the legislative bureau of government (中書省, Zhongshu Sheng), in the administration of Emperor Xizong, who had fled to Chengdu from the capital Chang'an in light of the attack that the major agrarian rebel Huang Chao launched on Chang'an late in 880.
[6] The people of Zhaoyi then asked the eunuch monitor Wu Quanxu (吳全勗) to act as military governor, but Meng rejected this (claiming that a eunuch should not be a governor) and put Wu under house arrest, instead claiming that he wanted the imperial government to send a replacement.
[7] In 885, by which time Huang Chao had been defeated and Emperor Xizong had returned to Chang'an, the powerful eunuch Tian Lingzi, who dominated Emperor Xizong's administration, offended the warlord Wang Chongrong the military governor of Hezhong Circuit (河中, headquartered in modern Yuncheng, Shanxi) and then tried to transfer Wang.
Wang resisted, and he and his ally Li Keyong the military governor of Hedong Circuit (河東, headquartered in modern Taiyuan, Shanxi) subsequently defeated the armies of Tian and Tian's allies Zhu Mei the military governor of Jingnan Circuit (靜難, headquartered in modern Xianyang, Shaanxi) and Li Changfu the military governor of Fengxiang Circuit (鳳翔, headquartered in modern Baoji, Shaanxi) and approached Chang'an.
When Xiao declined (claiming that his writing abilities had deteriorated), Zheng Changtu, who was then the deputy minister of defense (兵部侍郎, Bingbu Shilang) and the director of taxation, did so.
Subsequently, after the imperial officials escorted Li Yun back to Chang'an, claiming regent authorities, made Zheng chancellor de facto with the designation Tong Zhongshu Menxia Pingzhangshi (同中書門下平章事).
Further, he was enticed by the declaration issued by the eunuch Yang Fugong, who had succeeded Tian as the commander of the Shence Armies (神策軍) by this point, that anyone who killed Zhu would be given Jingnan Circuit.