Learning that gunpowder was developed around 850 AD make me think about all the things that it preceded such as the First Crusade and the battle of Hastings and I wonder why it seems that it took so long to become widespread in its use. Between the Silk Road and Mongol invasion it seems like it would have become immediately popular through the Middle East and Mediterranean for its obvious military applications in sieges and such. And why didn’t various gunpowder weapons such as fire lances and fire arrows travel far from China?