The Collapse of Central Authority

In January 763 AD, the eight-year An Lushan Rebellion—the most devastating civil war in Tang Dynasty history—reached its bloody conclusion when rebel leader Shi Chaoyi committed suicide after being cornered by his own general Li Huaixian. This marked the formal end of a conflict that had begun in 755 AD with An Lushan’s revolt from Fanyang (modern Beijing), but the aftermath would prove more consequential than the rebellion itself.

Emperor Daizong, facing imminent Tibetan invasions that would soon sack Chang’an, made a fateful decision: he pardoned all former An Lushan commanders in exchange for their nominal submission. This created the “Hebei Four”—Li Huaixian (Youzhou), Li Baochen (Chengde), Tian Chengsi (Weibo), and Xue Song (Zhaoyi)—who became de facto warlords controlling northeast China. The Tang court, having exhausted its military resources fighting the rebellion, could only watch as these former rebels established hereditary military regimes that would plague the dynasty for centuries.

The Warlords of Hebei

The four warlords shared striking similarities—all were ethnic minorities from the northeastern frontier, all had served as An Lushan’s lieutenants, and all possessed the pragmatism of survivors:

1. Li Huaixian (Youzhou/Lulong) – A Khitan officer who changed allegiances five times during the rebellion, ultimately gaining control of the strategic northern frontier. His territory would evolve into the notoriously rebellious Lulong Circuit.

2. Li Baochen (Chengde) – Originally named Zhang Zhongzhi, this Xi tribesman had served as An Lushan’s bodyguard before controlling the critical Taihang Mountain passes. His domain became the cavalry powerhouse of the Hebei region.

3. Xue Song (Zhaoyi) – Grandson of legendary Tang general Xue Rengui, his brief control of the economically vital Yongji Canal region ended with his early death, allowing Tang forces to reclaim the area.

4. Tian Chengsi (Weibo) – The most ruthless of the four, he created the infamous “Yajun” (牙兵) system—a private army of 10,000 elite troops that became the model for later warlord regimes. His Weibo Circuit would remain a thorn in the Tang’s side for generations.

The Birth of the Yajun System

Tian Chengsi’s innovation changed Chinese military history. Fearing both Tang reprisals and local uprisings after years of rebel atrocities, he:

– Conscripted all able-bodied males into his army
– Left only the elderly and weak for farming
– Selected 10,000 elite “Yajun” (tooth soldiers) as his personal guard

These Yajun weren’t just soldiers—they became a hereditary military caste with vested interests in maintaining the warlord system. Their loyalty followed paychecks rather than ideals, creating what historian David Graff calls “the world’s first professional military corporation.”

The Unraveling of Tang Authority

The consequences were profound:

1. Economic Devastation – Hebei’s once-prosperous lands became militarized zones. Contemporary records describe villages where “the strong died by sword, the weak filled ditches.”

2. Cultural Divide – The northeast developed a distinct identity, with later Tang poets lamenting that “north of the Yellow River, customs turned barbaric.”

3. Political Fragmentation – The Tang never regained true control over the northeast. Subsequent emperors could only play warlords against each other through a system historian Denis Twitchett termed “containment through recognition.”

4. Military Precedent – The Yajun model spread nationwide. By the 9th century, even “loyal” Tang garrisons operated like independent entities, culminating in the Huang Chao Rebellion that toppled the dynasty.

Legacy: The Roots of Late Imperial China

The An Lushan aftermath shaped China’s trajectory for centuries:

– Five Dynasties Period – The Later Tang (923-936) emerged directly from the Hedong warlord system
– Song Dynasty Reforms – Song Taizu’s centralization policies were direct responses to Tang military decentralization
– Borderland Identity – The northeast’s separate identity persisted through the Liao, Jin, and Qing dynasties

As historian Wang Gungwu observed, “What began as a temporary expedient in 763 became the enduring pattern of Chinese politics—the center’s perpetual struggle to control armed peripheries.” The Yajun’s descendants would continue influencing Chinese history until the 20th century, proving that the true end of the An Lushan Rebellion came not in 763, but in 1911 with the fall of China’s last imperial dynasty.