Origins
The direct trigger of Lü Bu's Seizure of Yanzhou was one of Cao Cao's strategic overreaches. To avenge his father, he campaigned east against Xu Province and Tao Qian, committing his whole force and leaving his base province of Yanzhou empty of troops—precisely the breeding ground for rebellion [c:16162]. The deeper origin lay in the latent rift between Cao Cao and Yanzhou's local gentry and magnates: Zhang Miao had been Cao Cao's old friend, yet under Chen Gong's persuasion he defected. Chen Gong laid bare Zhang Miao's situation in a word—"with a host spanning a thousand li, yet controlled by another"—so why not, while Cao Cao was away on campaign, welcome the valiant Lü Bu, the foremost warrior of the age, and together take Yanzhou to pursue hegemony [c:16162]. These words struck precisely at the local power-holders' unwillingness to remain subordinate, and the rebellion was thereby ignited.
Forces Involved
The rebel side was a combination of "local magnates plus an exiled fierce general." The brothers Zhang Miao and Zhang Chao represented Yanzhou's native forces, providing the foundation and the legitimacy; Chen Gong was the chief strategist, responsible for the planning; and Lü Bu was the guest general who had just drifted in seeking refuge—the bravest of the age yet repeatedly marginalized—providing the military striking power [c:16161]. Under Lü Bu, his eight stalwart generals such as Zhang Liao and Zang Ba formed his core fighting strength [c:16164]. Cao Cao's side took the shape of "main force on campaign plus a caretaker team": Cao Cao led the main force in person abroad, while Xun Yu and Cheng Yu, as the caretaker advisors, held to the death the three cities of Juancheng, Dong'e, and Fan, becoming the last fulcrum that kept the whole board from being lost [c:16162]. Fierce generals such as Dian Wei and Xu Chu then played key roles in the subsequent counterattack.
Key Turning Points
The battle had three turning points. The first was Xun Yu and Cheng Yu holding the three cities—had these three strongpoints also fallen, Cao Cao would truly have been "homeless"; it was precisely this foothold that allowed him to bring his army back and counterattack [c:16162]. The second was the seesaw at Puyang: Cao Cao, defeated in the opening battle, withdrew, and on a night raid against the camp ran into an ambush and was trapped in the fire, nearly dying beneath Lü Bu's halberd, saved only when Dian Wei drove off the pursuers with flying halberds and fought desperately to rescue him [c:16166][c:16167]. The third was the intervention of natural disaster—in the first year of Xingping a great locust plague arose, grain prices soared, and there was cannibalism; both sides exhausted their provisions and were forced to withdraw to forage, and the war unexpectedly entered a "cooling period" [c:16168]. This calamity objectively gave Cao Cao time to catch his breath and regroup.
Suppression and Outcome
The following year, once Cao Cao's strength had recovered, Cheng Yu advised advancing to take Puyang; Cao Cao, with Xu Chu and Dian Wei as vanguard and the six generals Xiahou Dun, Xiahou Yuan, Li Dian, and Yue Jin closing in on Lü Bu, found Lü Bu unable to hold them off and beaten back to the foot of the walls [c:16170]. At this point, within Puyang, Lady Tian defected and refused to admit Lü Bu, becoming the last straw that broke the rebel army—Lü Bu had no choice but to lead his troops off to Dingtao, Chen Gong escorting his family out of the city, and Cao Cao thus regained Puyang [c:16171]. This rebellion, lasting over a year, was at last put down, but the cost was severe: Cao Cao had almost lost his entire base and narrowly escaped death, and Yanzhou too was gravely weakened by the fires of war and famine.
Historical Resonance
The Yanzhou rebellion taught Cao Cao an unforgettable lesson. After the rebellion was put down, when he again wished to attack Xu Province out of old grudge, Xun Yu forcefully remonstrated, citing how Gaozu held Guanzhong and Guangwu held Henei, stressing that Yanzhou was the foundational ground for "deep roots and a firm base" and must not be abandoned—trading the great for the small, forsaking the root in pursuit of the branch [c:16169]. These words led Cao Cao to thoroughly establish the strategic principle of "first secure the base, then plan expansion," turning instead to raid the Chen region eastward to forage and to crush the Yellow Turban remnants to feed his army [c:16169]. In this sense, though Lü Bu's rebellion was a crisis that nearly overturned Cao Cao, it also tempered the mature strategic thinking with which he afterward managed his base of operations. It reveals a law of the age of chaos: however strong one's offensive capability, without a firm rear to support it, all can vanish in a single defection.