In 208, Cao Cao marched south with his army hoping to quickly unify the empire. Liu Biao's son Liu Cong surrendered Jing Province and Cao was able to capture a sizable fleet at Jiangling. Sun Quan, the successor to Sun Ce in the lower Yangtze, continued to resist. His advisor Lu Su secured an alliance with Liu Bei, himself a recent refugee from the north, and Zhou Yu was placed in command of Sun Quan's navy, along with a veteran general who served the Sun family, Cheng Pu. Their combined armies of 50,000 met Cao Cao's fleet and 200,000-strong force at Red Cliffs that winter. After an initial skirmish, an attack beginning with a plan to set fire to Cao Cao's fleet was set in motion to lead to the decisive defeat of Cao Cao, forcing him to retreat in disarray back to the north. The allied victory at Red Cliffs ensured the survival of Liu Bei and Sun Quan, and provided the basis for the states of Shu and Wu.