[Why] Early Western Jin overturned the Wei policy of keeping kinsmen out of power and broadly enfeoffed Sima clansmen with troops of their own. The accession of the cognitively limited Emperor Hui triggered violent harem power struggles. [What] Eight imperial kinsmen with troop commands, incited by Empress Jia Nanfeng, fought each other ferociously, reducing Luoyang and Chang'an to slaughterhouses. They repeatedly recruited northern nomadic forces as mercenaries to fight their own kin. [Who] Emperor Hui was an incompetent puppet of the throne; Jia Nanfeng was the venomous empress who sparked the strife. The eight princes, blind in their pursuit of power, destroyed the very foundation of the empire to win their thrones. [How] The war ravaged the imperial core of Western Jin and lost control of the frontier defenses entirely. It directly triggered northern nomadic invasions and the Southward Migration of Noble Clans, becoming a catastrophic civil war.
Why
The historic event of War of the Eight Princes represents a key developmental peak of the Huaxia dynastic system. A catastrophic civil conflict that reshaped ethnic distribution. By establishing this moral or administrative benchmark, it continues to shape the structural and philosophical fabric of ancient Chinese statecraft.