As we all know, the nation-state of China has risen and fallen many times, often collapsing or getting invaded by the northern hordes but always reunifying.
How could we have a permanently shattered China? It could even happen if China was never unified under the Qin Dynasty, or perhaps China just falls and doesn’t reunify.
I’m aiming sometime around the Medieval period.
What would be the easiest possible way this could happen and what would be the implications on East Asia and the world as a whole?