208, Sun Quan defeated and killed Liu Biao's vassal Huang Zu at the Battle of Jiangxia, seizing most of Huang's territory at Jiangxia (江夏; present-day Xinzhou District, Wuhan, Hubei). While Cao Cao was attacking the Yuan clan in northern China, Liu Bei fled south to join Liu Biao and became a vassal under the latter, who stationed him at the northern border in Xinye County to keep Cao Cao at bay. An initial Cao attack on Liu Bei was repelled during the Battle of Bowang (202). Red Cliffs campaign (208–209) Cao Cao's invasion of Jing Province (208) In 208, Cao Cao launched a southern campaign to conquer Liu Biao's Jing Province. Liu Biao was ill and dying when a succession struggle broke out between his sons Liu Qi and Liu Cong. After Huang Zu's defeat, Liu Qi was appointed by Liu Biao as Administrator of Jiangxia, which was previously governed by Huang. Liu Cong, who was favoured by Liu Biao's second wife Lady Cai (because he married her niece), remained in Jing Province's capital, Xiangyang. Liu Cong became the new Governor of Jing Province after his father's death. Fearing that he might be caught in a war on two fronts (Cao Cao in the north and Liu Qi in the southeast), Liu Cong surrendered to Cao Cao, and most of Jing Province came under Cao Cao's control. Liu Bei was unwilling to submit to Cao Cao and fled south. Along the way, one of Cao Cao's light cavalry units caught up with Liu Bei's retreating forces (which included civilians) and defeated them at the Battle of Changban. Liu Bei escaped with his life and fled to Dangyang (當陽; in present-day Yichang, Hubei). In Jiangdong, Sun Quan felt threatened by Cao Cao's approaching army and sent Lu Su to discuss forming an alliance with Liu Bei and Liu Qi against Cao Cao. Cao Cao wrote Sun Quan a letter, intended to intimidate the latter into submitting. Cao Cao's army was estimated to be 220,000 men strong, although Cao himself claimed that he had 800,000 troops. Sun Quan had 30,000 men, while Liu Bei and Liu Qi's combined forces totalled about 10,000. Many of Sun Quan's followers, including Zhang Zhao, strongly advocated surrender because of Cao Cao's overwhelming forces. However, Sun Quan refused as he agreed with Zhou Yu and Lu Su's view that Cao Cao might not let him off even