Liu Biao
In 207, Cao Cao planned a campaign to conquer the Wuhuan in the north, but was apprehensive that Liu Biao might attack his base but he was assured by Guo Jia that Liu Biao would not do so for fear of Liu Bei being more powerful than he was. Cao Cao agreed and Guo Jia's point was proven later, when Liu Biao refused to attack Xu when Liu Bei advised him to do so. When Cao Cao returned from Liucheng. Liu Biao told to Liu Bei: "I didn't adopt your proposal and now I lost this great opportunity." Liu Bei answered: “Now the empire is in chaos and every days there are battles. What seem to be a good opportunity may present himself later. If you are able to respond to them accordingly then this isn't worth regret."