When the Romans were deep into empire building rampaging through Europe and subjugating the Gauls, the Goths, the Pritons (the original name for the Britons) and others the Chinese had discovered gunpowder and were having great fun at festivals.
Had gunpowder travelled to Europe the Romans would have been stropped in their tracks.
History is made by war, we are told but actually countries are made by wars. History is made by what we don’t know.