Cao's army reached Pengcheng, Chen Gong told Lü Bu, "We should attack the enemy now, since our troops have rested well while the enemy is weary. We're sure to win." Lü Bu replied, "Why don't we wait for them to attack first? After that we'll destroy them in the Si River." When Cao Cao's attacks increased in intensity, Lü Bu went up the White Gate Tower (白門樓; the viewing platform above the main gate in the south of Xiapi) and told his men, "Cao Cao has no intention of finding trouble with you. I should surrender to the wise lord." Chen Gong said, "The treacherous Cao Cao is no wise lord! Surrendering to him is like hitting a rock with an egg! How can you expect to live (after you surrender)?" Lü Bu sent Xu Si (許汜) and Wang Kai (王楷) to request urgent aid from Yuan Shu. Yuan Shu said, "Lü Bu refused to send his daughter here, so it's expected that he'll meet his doom. Why does he seek help from me again?" Xu Si and Wang Kai replied, "If Your Highness doesn't save Lü Bu, you'll be courting your own doom. If Lü Bu is destroyed, Your Highness will be next." Yuan Shu then prepared his troops and claimed that he would be sending reinforcements to Lü Bu. In the meantime, Lü Bu thought that Yuan Shu was reluctant to help him because he did not send his daughter to Yuan Shu, so, one night, he tied his daughter to himself and attempted to break out of the siege. However, they encountered Cao Cao's soldiers, who fired arrows at them, so they had no choice but to return to Xiapi. Lü Bu led some 1,000 riders out of the city to engage the enemy, but lost the battle so he retreated back to Xiapi and did not dare to venture out. Lü Bu ordered Chen Gong and Gao Shun to defend Xiapi, while he personally led some horsemen to attack Cao Cao's supply routes. However, before he left, his wife told him, "General, I know you want to attack Cao Cao's supply lines, but Chen Gong and Gao Shun can't get along with each other. If you leave, they may not work well together in defending the city. If a mishap occurs, what will become of you, General? I hope you'll consider this carefully and not be