Chen Gong : biography
Along the journey, they passed by the house of Lü Boshe, a sworn brother of Cao Cao’s father. There, they killed Lü Boshe’s family by mistake, while Cao Cao personally murdered Lü in cold blood later. (See the article on Lü Boshe for details.) Chen Gong was shocked by what he witnessed. That night, as Cao Cao slept, Chen Gong considered killing him, but thought it unrighteous to do so. He instead left Cao Cao and travelled to his own hometown of in Dong commandery (東郡; near present-day Puyang, Henan).
Battle of Puyang
Chen Gong’s most brilliant, albeit fictitious, maneuver came during the Battle of Puyang, in which Cao Cao’s force laid siege on Lü Bu in the city of Puyang (濮陽). The incident was described in Chapter 12. Chen Gong, who was then serving Lü Bu, plotted to lure Cao Cao into the city by having a local baron send a letter to Cao Cao feigning to collude with the latter. The delighted Cao Cao personally led a force deep into the city before realizing the trap. At a signal, fires were lit at all of the four city gates and Lü Bu troops cut off the evasion routes.
Separated from his men in the chaos, Cao Cao desperately sought an escape. Heading towards the north gate, he ran face-to-face into Lü Bu. Using a hand to cover his face, Cao Cao spurred his horse onward and past the enemy but Lü Bu spun around and caught up with him. Not able to recognize the warlord, Lü Bu knocked on Cao Cao’s helmet with his halberd and asked, "Where is Cao Cao?" Cao Cao pointed behind and said, "The one on the dun is him." Lü Bu then gave up his true target.
As Cao Cao galloped to the city gate his horse was hit by a falling beam on fire. While trying to push the beam off, Cao Cao scalded his arms and burnt much of his hair. However, he finally managed to escape with his life under the escort of Xiahou Yuan and Dian Wei. Much later in Chapter 60 of the story, when Zhang Song, an emissary from Liu Zhang, mocked the failures of Cao Cao, the Battle of Puyang was cited among other classic battles including the Battle of Wancheng and Battle of Red Cliffs.