Battle of Zhuolu
Legend has it that during Emperor Yan"s reign, the leaders of all tribes and clans fought against one another to plunder fortunes, which caused great misery to the common people. Among them, Chiyou was the most atrocious. The Yellow Emperor summoned other clans to launch a fierce battle with Chiyou at Zhuolu (present Zhuolu County of Hebei Province). This is the earliest "war" that has ever been recorded in Chinese history.
The battle ended up with the victory of the Yellow Emperor, who thereby occupied the vast Central Plains area which was suitable for husbandry and crop cultivation. Moreover, the Yellow Emperor was then supported by many other tribes, which laid a foundation for him to become the chief of the tribe league.