The next morning,Sun Ch'uan called all his civil and army officials together and asked Chou Yu to make the decision for him.Chou Yu said,"From the military point of view,Ts'ao Ts'ao's expansion to the south will be limited by four problems:First, he doesn't have a stable home front.Second, people from north China are usually not good at naval battles.Third, it is winter time now,and their cavalry is short of fodder. Fourth,they are not used to the weather and living conditions in the south."