The Tang Dynasty’s Crisis of Authority

The mid-Tang Dynasty (618-907 CE) witnessed a dangerous shift in imperial power dynamics as eunuchs transformed from palace servants into kingmakers. Against the backdrop of the devastating An Lushan Rebellion (755-763) that shattered central authority, Emperor Daizong’s reign (762-779) became a battleground between scholar-officials, military governors, and ambitious eunuchs. Among these power brokers, Cheng Yuanzhen emerged as perhaps the most destructive figure—a master manipulator whose actions accelerated the Tang’s decline through calculated betrayals, military blunders, and systemic corruption.

From Obscurity to Power: Cheng’s Ascent

Born in Jingzhao Sanyuan, Cheng entered palace service as a castrated youth during Emperor Xuanzong’s late reign. His early career as Deputy Commander of the Flying Dragon Stables placed him under Li Fuguo—the first Tang eunuch to wield chancellor-level authority. Cheng’s rise began during the 762 succession crisis when he helped Li Fuguo eliminate Empress Zhang and Prince Li Xi.

Empress Zhang represented a recurring Tang phenomenon—ambitious imperial women inspired by Wu Zetian’s precedent. During the 756 An Lushan Rebellion, she demonstrated remarkable leadership, protecting then-Crown Prince Suzong during their perilous flight from Chang’an. However, her subsequent political maneuvers, including the wrongful execution of Prince Li Tan, made her enemies. When Emperor Suzong fell ill, she attempted a coup against Li Fuguo’s faction, only for Cheng and Li Fuguo to strike first—dragging her from the dying emperor’s bedside and installing Daizong as emperor.

The Puppetmaster’s Reign

After engineering Li Fuguo’s 762 assassination (reportedly via decapitation with his arm sent to Xuanzong’s tomb), Cheng monopolized power through ruthless tactics:

1. Neutralizing Military Heroes
Cheng systematically undermined An Lushan Rebellion heroes like Guo Ziyi, whom he had demoted to tomb-building duty. General Lai Tian—a celebrated commander nicknamed “Iron-Chewer”—was falsely accused of colluding with rebels and executed, causing widespread outrage among frontier generals.

2. Controlling Information Channels
The Zizhi Tongjian records how Cheng isolated Emperor Daizong: “All memorials must first pass through the Cavalry General [Cheng], not even the chancellors may decide matters.” This created fatal intelligence gaps when Tibetan forces invaded in 763.

3. Provoking Regional Defiance
Cheng’s persecution of officials like Chancellor Pei Mian (exiled for opposing Li Fuguo) eroded central authority. When Tibet attacked Chang’an, key generals like Li Guangbi refused mobilization, fearing Cheng’s treachery more than foreign invaders.

The Fall of Chang’an and Cheng’s Downfall

Cheng’s disastrous mishandling of the 763 Tibetan crisis marked his end. Ignoring invasion warnings, he left Chang’an defenseless until Tibetans occupied the capital for 15 days—the only time between 316-881 CE that nomadic forces captured China’s heartland.

The catastrophe triggered an unprecedented censure from scholar-official Liu Kang: “If Your Majesty wishes to preserve the empire, behead Cheng Yuanzhen and proclaim it to the world!” Temporarily exiled, Cheng attempted a clandestine return wearing women’s clothes—a final humiliation before his mysterious death en route to exile.

Legacy: The Eunuch Paradox

Cheng’s career exposed the Tang’s structural vulnerabilities:
– Militarization’s Cost: Reliance on regional commanders during the An Lushan Rebellion created centrifugal forces that eunuchs like Cheng exacerbated through mistrust.
– Information Autocracy: By monopolizing access to the emperor, eunuchs could paralyze governance—a flaw later dynasties addressed through elaborate memorial systems.
– Symbolic Subversion: Cheng’s induction into the Lingyan Gallery—traditionally honoring loyalist heroes—epitomized how eunuch power corrupted Tang political culture.

Though contemporaries celebrated Cheng’s removal as a triumph, they failed to recognize the systemic nature of eunuch power. Subsequent decades saw even more dominant eunuchs, culminating in the 835 Sweet Dew Incident’s bloody purge. The Tang never solved this institutional dilemma, leaving later dynasties to grapple with balancing imperial authority against bureaucratic and palace interests—a challenge that shaped Chinese governance for centuries.