Coming to power after the death of his brother, John soon became embroiled in a series of border wars with the French, gaining and losing land along the French coastline. When several English barons rebelled against John in 1215 over his refusal to accept the Magna Carta, a document that had been crafted to limit John's powers, they joined the French and instigated the First Baron's War.
Backed by members of the Templar Order, and even by the independent Assassin William of Cassingham, John attempted to keep the French in check. The rebellious barons, including the majority of the English Assassins and their leader Robert Fitzwalter, managed to push John's forces from the French mainland and even capture several castles on the English island. Over the next year, a stalemate would develop, with neither side gaining any significant advantage.