After executing Cai Mao, Cao Cao summons Cai Zhong and Cai He of the same family and has them surrender falsely to Jiangdong. The two say their wives and children are all in Jing Province, so how could they be disloyal, and promise to bring back the heads of Zhou Yu and Zhuge Liang. They cross to the south bank in a few boats with five hundred men and weep that they want to avenge their elder brother. Zhou Yu is delighted and puts the two in the vanguard with Gan Ning.
Zhou Yu calls Gan Ning aside. Those two did not bring their families, so this is no true surrender. They are spies sent by Cao Cao. I mean to take his trick and turn it round, and let them carry news back. Treat them warmly on the surface and keep watch underneath. When Lu Su says the two men’s surrender must be false and they should not be accepted, Zhou Yu rebukes him, asking how he can welcome the scholars of the realm if he is so suspicious.
Lu Su withdraws without a word and goes to Kongming, who only smiles. When Lu Su asks why, Kongming says, I am smiling because you do not see Gongjin’s plan, Zijing. With the great river between, it is hard for spies to come and go. Cao Cao has sent Cai Zhong and Cai He, so Gongjin will turn them round and have them carry news. In war one does not shrink from deceit, and Gongjin’s plan is right. Only then does Lu Su understand.