In 199 AD, after suppressing unrest in Henei, Cao Cao stationed his troops at Aocang. Why did he choose to garrison his forces at Aocang near Luoyang instead of returning directly to Xudu?
The Conspiracy Unfolds in the Court
While Cao Cao was away on military campaigns, a rebellion led by Dong Cheng, General of Chariots and Cavalry, was quietly unfolding within the imperial court. Cao Cao shrewdly detected the issue and, among numerous potential threats, identified Dong Cheng as the most imminent danger.
Since relocating the emperor to Xuxian, Cao Cao had effectively consolidated control over the imperial court. Over time, this naturally bred resentment among others. Dong Cheng, General of Chariots and Cavalry, claimed to possess a secret edict from Emperor Xian and attempted to recruit Liu Bei to join him in opposing Cao Cao. However, Liu Bei did not take immediate action.
Xuande admitted at last, “I had to test you.” Dong Cheng then produced the secret edict. Dismay and indignation welled up in Xuande as he read the Emperor’s sacred words.
Next, Dong Cheng handed him the loyalists’ pledge bearing six signatures: Dong Cheng, general of Cavalry and Chariots; Wang Zifu, an official in the Ministry of Works; Chong Ji, commandant of the Changshui command; Wu Shi, court counselor; Wu Zilan, General of Manifest Trust; and Ma Teng, governor of Xiliang. “Since the Emperor has charged you with the task of punishing the traitor,” Xuande said, “I commit myself to the cause and offer my fullest devotion.”
— Romance of the Three Kingdoms, Chapter 21
After failing to sway Liu Bei, Dong Cheng turned to Wang Zifu, Partial General, stating, “Guo Si repelled Li Jue’s tens of thousands of troops with just a few hundred men. Thus, success depends on whether you and I are of one mind.” Upon hearing Dong Cheng’s rebellious plan, Wang Zifu was terrified, fearing insufficient military strength, and repeatedly declined. Dong Cheng then revealed his trusted allies, including Zhong Ji and Wu Shuo, ultimately persuading Wang Zifu to join the conspiracy.
Cao Cao’s Garrison at Aocang
Now, returning to the initial question: Why did Cao Cao garrison troops at Aocang? How does this relate to the coup brewing in the court?
Cao Cao’s decision to station troops at Aocang while confronting Dong Cheng likely had multiple reasons. However, the most crucial was to sever the passage between the Central Plains and the northwest. As a general from the northwest, Dong Cheng posed a risk of fleeing with Emperor Xian back to Guanzhong. Cao Cao also needed to prevent Dong Cheng from colluding with northwestern warlords like Ma Teng. By confining Dong Cheng to the Central Plains, Cao Cao effectively isolated him.
With Aocang under his control, Cao Cao cut off Dong Cheng and Emperor Xian’s escape route.
Cao Cao’s Patience and Strategy
In fact, Cao Cao had likely long been aware of Dong Cheng and Emperor Xian’s scheming. However, he waited for the right opportunity and a justifiable pretext to move against his opponents. Without solid reasoning, Cao Cao could not act against Dong Cheng. Thus, he chose to wait—a reminder that rushing often fails to resolve issues, while seizing the right moment can solve everything at once. This opportunity was ultimately provided by Liu Bei.
The Turning Point: Liu Bei’s Betrayal
Earlier, to prevent Yuan Shu from advancing northward to join Yuan Tan in Qingzhou, Cao Cao wanted someone to block him. Cao Cao had sent Liu Bei to attack Yuan Shu in his way to join Yuan Tang and Yuan Shao. However Liu Bei seized the opportunity to break free from Cao Cao’s control. After defeating Yuan Shu, Liu Bei suddenly turned back and seized Xuzhou, declaring independence. Upon learning that Liu Bei had taken Xuzhou, Dong Cheng believed he had gained another powerful ally and grew increasingly reckless. As Dong Cheng reveled in his perceived advantage, Cao Cao suddenly issued an imperial edict in the emperor’s name, accusing Dong Cheng of colluding with Liu Bei to overthrow the court. This branded both Dong Cheng and Liu Bei as traitors. Cao Cao subsequently crushed Dong Cheng and his faction in Xuchang, and Dong Cheng’s daughter, Consort Dong, was also executed. As a grave threat to Cao Cao, Dong Cheng had to be eliminated root and stem.
The Rationale Behind Cao Cao’s Deliberate Approach
A closer examination of this history reveals that Cao Cao could have easily killed Dong Cheng without much effort. Yet, he deployed tens of thousands of troops to garrison Aocang and patiently waited for the right moment. Cao Cao knew that killing Dong Cheng outright would be seen as settling a personal grudge, openly positioning himself against Emperor Xian.
Sometimes, when the opportunity has not yet arrived, one must prepare and wait patiently. Cao Cao quietly observed Dong Cheng’s actions from behind the scenes. He waited for half a year until the opportunity finally came, then eradicated his formidable adversary in one stroke. Once again, Cao Cao emerged as the savior of the Han dynasty.
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