Battle of the Fei River

Fu Jian had unified northern China out of a patchwork of conquered kingdoms and in 383 marched south to finish the job, with an army his chroniclers said could dam a river by throwing in their whips. The two forces met across the Fei, and the southern commanders asked the northerners to pull back a little so a battle could be fought on open ground. Fu Jian agreed, intending to strike as they crossed. The withdrawal did not stop: his army was a coalition of recently conquered peoples with no reason to die for him, someone at the back shouted that the battle was lost, and the retreat turned into a rout that destroyed the army without much fighting at all. Fu Jian's empire came apart within two years and China stayed divided for another two centuries.

The sources are the Book of Jin and the Zizhi Tongjian, compiled centuries after the event and shaped into a moral fable about a ruler destroyed by overconfidence, which is a reason to treat the famous details sceptically rather than a reason to discard them. Almost no modern historian accepts the 800,000 figure, and the more interesting scholarly argument is about the mechanism: whether the fatal withdrawal was a genuine tactical agreement, a southern trick, or a later rationalisation of an army that simply came apart. The battle carries enormous weight in Chinese historiography as the moment the southern dynasties survived and a distinct southern Chinese polity became durable. Even the site is unsettled, since the Fei of the sources cannot be matched confidently to any single modern watercourse.