Jiang Gan’s forged-letter incident reverses an attempt at persuasion into a strategic disaster for Cao Cao. Sent to use his old friendship with Zhou Yu to induce a defection, Jiang Gan discovers that he cannot change Zhou’s allegiance; instead, he steals a letter staged to look like proof that Cai Mao and Zhang Yun are secretly plotting against Cao Cao. Cao Cao accepts the apparent evidence, orders the two commanders executed, and recognizes the deception only after their deaths. The episode shows how Zhou turns an opponent’s mission into an instrument against him—and how suspicion, once given the appearance of documentary proof, can inflict damage that cannot be undone.

Background and Mission

At the time, Cao Cao is seeking a way to defeat Zhou Yu. Jiang Gan presents himself as a suitable emissary because he and Zhou were old school friends, and he believes friendship may help bring Zhou over to Cao Cao’s side. Cao Cao agrees to the attempt, and Jiang Gan goes to visit him.

The plan meets a carefully managed display of strength. Zhou Yu holds a large party attended by his military commanders, ensuring that Jiang Gan sees the scale of the southern forces and their preparations. Zhou also invites his visitor to stay the night. The visit is therefore not a private opening for reconciliation: Zhou uses hospitality and spectacle to make clear that Jiang Gan is unlikely to persuade him, while preparing to exploit the emissary’s presence for his own purposes.

The Staged Letter

As the evening proceeds, Zhou appears increasingly intoxicated and behaves as though he has lost command of himself. He invites Jiang Gan to sleep in his tent, then pretends to be deeply asleep. Jiang Gan has already concluded that he has no prospect of changing Zhou’s allegiance. While Zhou appears oblivious, Jiang explores the tent and finds a letter that purports to come from Cai Mao and Zhang Yun.

The letter presents the two commanders as men who were forced to serve Cao Cao but have since maneuvered into a position from which they can kill him and deliver his head to Zhou. Its allegations address a danger Cao Cao would have reason to take seriously: the supposed plot is not merely a claim of private disloyalty, but a threat against his life. Yet the passage identifies the letter as a deception, not genuine evidence of a conspiracy. Zhou’s apparent drunkenness and sleep have enabled Jiang to discover and take the planted document, while concealing its real purpose from him.

Theft and Report to Cao Cao

Jiang Gan steals the letter, calculating that even if he has failed to bring Zhou over, the document may win Cao Cao’s approval. He spends an anxious night afraid that Zhou will wake or notice the theft, then slips away early in the morning and makes his escape. The interval between finding the letter and presenting it gives the episode its tension: Jiang has secured what he thinks is valuable proof, but must get it out of Zhou’s camp without being discovered.

Back at Cao Cao’s camp, Jiang first admits that Zhou will not change sides. Cao Cao reacts angrily. Jiang then claims to have found something more important, but says he can disclose it only in private. Once the room has been cleared, he shows Cao Cao the apparent letter of betrayal. That presentation transforms a stolen, unverified document into a political and military accusation delivered directly to the commander with power to act on it.

Executions and Strategic Consequences

Cao Cao responds by ordering the immediate execution of Cai Mao and Zhang Yun. Only when their heads are brought in does he realize that he has been deceived. He nevertheless refuses to acknowledge the mistake, unable to bear the humiliation. His commanders are appalled: the decision has removed two men who understood marine warfare, and the loss is compounded by the fact that Cao Cao acts before establishing that the letter is authentic.

The consequences extend beyond the mistaken deaths. When the news reaches Zhou Yu, he smiles with relief because Cai Mao and Zhang Yun were the commanders who worried him most. The forged document has thus achieved for Zhou what Jiang Gan’s original mission was meant to prevent: it weakens Cao Cao’s position without bringing Zhou any closer to defection. Zhou’s relief also confirms the strategic value of the two dead commanders to the opposing side.

Narrative Function

The incident builds its reversal through a chain of mistaken readings. Jiang Gan reads a planted letter as an opportunity to recover his standing with Cao Cao; Cao Cao reads its allegations as grounds for immediate action; only after the order has been carried out does he recognize that the evidence was false. Zhou, by contrast, has arranged the encounter so that Jiang’s attempt to serve Cao Cao delivers an advantage to Zhou. The decisive weapon is not a battle formation but a document whose apparent authority outruns any verification.

The episode belongs to the novel’s larger portrayal of a political world shaped by betrayal, intrigue, and repeated battles. Its particular force comes from joining deception to an irreversible consequence: the commanders’ naval expertise is lost at the very moment Cao Cao needs military strength against Zhou. The incident is therefore both a successful act of counterintelligence by Zhou and a failure of judgment within Cao Cao’s camp, with the stolen letter serving as the hinge between them.