First Barons' War
The First Barons' War (1215–1217) was a civil war in the Kingdom of England in which a group of rebellious major landowners (commonly referred to as barons) led by Robert Fitzwalter waged war against King John of England. The conflict resulted from King John's disastrous wars against King Philip II of France, which led to the collapse of the Angevin Empire, and John's subsequent refusal to accept and abide the "Magna Carta", which he had sealed on 15 June 1215.