Robin Hood Prince of Thieves

Historical Setting: 1194 AD

• In the movie the Sheriff of Nottingham hires Celtic mercenaries to help him defeat Robin Hood and his men. Historically, the Romans defeated and assimilated all of the Celts, except for those in Ireland. But the Irish of 1194 and the Celts of the pre-Roman times barely resembled each other. By 1194 Britain and Ireland had already had contact, and the "cannibal" myths of old had probably been retired as Ireland was a mostly Christian country by this time. In 1177 Prince John, Richard the Lionheart's brother, was named Lord of Ireland, and he made his first visit to the country in 1185. So in 1194 there would be no Celtic mercenaries for the Sheriff to call, only Irish subjects. 
• In the movie, though the word gunpowder is never mentioned, it is clear that is what the magic black powder used by Robin Hood's men is supposed to be. Historically, gunpowder first appeared in China, and was used in fireworks by the 10th century. The Arabic people discovered it next by the 1300s. It was only in the 1500s that it first made an appearance in European weapons, so there is no way Robin Hood or his men could have used gunpowder in 1194 Britain.

Sources

Encyclopedia Britannica.

   Micropaedia. Volume II, pg 64.

Foster, R.F. The Oxford Illustrated History of Ireland. New York: Oxford University Press, 1989.