Fu Jian was a capable ruler who promoted ethnic harmony and recruited talented advisors like Wang Meng.
By 376 AD, he had unified northern China, ending the chaos of the Sixteen Kingdoms period in that region.
In 383 AD, despite warnings from his generals, he launched a massive invasion of 870,000 troops against the Eastern Jin dynasty.
His overconfidence led to a catastrophic defeat at the Fei River, causing his empire to rapidly collapse shortly after.