[Why] At the end of the Eastern Han, the Yellow Turban Rebellion had collapsed central authority and the realm dissolved into warlord territories. After pacifying the north, Cao Cao led hundreds of thousands of land and naval forces southward to swallow the south in one unifying campaign. [What] Facing Cao Cao's overwhelming advantage, Sun Quan and Liu Bei formed a geopolitical alliance to resist. The allied commanders Zhou Yu and Huang Gai executed a brilliant fire attack at Red Cliffs that incinerated Cao's fleet and forced him to retreat north in defeat. [Who] Zhou Yu was the composed and commanding Jiangnan general who led with feathered fan in hand. Zhuge Liang was the brilliant diplomat-strategist of the alliance, while Cao Cao suffered his life's worst defeat through tactical complacency and plague among his troops. [How] Red Cliffs preserved the independence of Jiangnan and Bashu and shattered Cao Cao's grand plan of rapid national unification. It became the watershed event that fractured the unified Han empire into the tripartite Three Kingdoms.
Why
The historic event of Battle of Red Cliffs represents a key developmental peak of the Huaxia dynastic system. Fragmenting the unified Han empire into the Three Kingdoms. By establishing this moral or administrative benchmark, it continues to shape the structural and philosophical fabric of ancient Chinese statecraft.