John of England
As part of the war, Arthur attempted to kidnap his own grandmother, Eleanor of Aquitaine, at Mirebeau, but was defeated and captured by John's forces. Arthur was imprisoned first at Falaise and then at Rouen. After this, Arthur's fate remains unknown, but it is believed that he was murdered by John. Assuming that he was murdered, Brittany, and later Normandy, rebelled against John. John also imprisoned his niece, Eleanor. Through deeds such as these, John acquired a reputation for ruthlessness.