(From "Romance of the Three Kingdoms")  

In 208 AD, the weakened Eastern Han dynasty was ruled by a puppet emperor, Xian.  The true power lay in the hands of Cao Cao, who declared himself prime minister of the kingdom.  In southern China, Liu Bei of Shu Han controlled the western region, while Sun Quan, King of Wu, ruled the eastern lands.  On the pretext of reuniting China, Cao Cao took an army of 800,000 soldiers to put down the "rebels".   Liu and Sun formed an uneasy alliance to repel the northerners.  Knowing they had less than one tenth of Cao Cao's manpower, they decided to use their naval superiority and their knowledge of their winter storms to outwit the Han army.  With the shrewd leadership of Zhou Yu, the viceroy of Wu, and the brilliant strategies of the cunning Zhuge Liang, Liu Bei's trusted advisor, the underdogs handed Cao Cao a decisive defeat at Red Cliffs.   Eastern Han fell not long after that, and China was plunged into decades of civil war, followed by shortlived dynasties for the next few centuries.  Not till the Tang dynasty in the seventh century was there finally peace and a unified China.