The First Barons' War (1215–1217) was a civil war in the Kingdom of England in which a group of rebellious major landowners led by Robert Fitzwalter waged war against King John. 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 by Magna Carta, which John had sealed on 15 June 1215.