Editing Arthur I, Duke of Brittany (section)

==Battle against John of England==
[[File:Falaise chateau guillaume conquerant 2.jpg|thumb|upright=1.37|The [[Château de Falaise]] in [[Normandy]],  where Arthur was imprisoned by his uncle [[John I of England|King John]]]]
{{Further|French invasion of Normandy (1202–1204)}}
After the signing of the Treaty of Le Goulet, and feeling offended by Philip, Arthur fled to John, his uncle, and was treated kindly, at least initially. However, he later became suspicious of John and fled back to [[Angers]]. Some unidentified source said that in April 1202, Arthur was again betrothed, this time to [[Marie of France, Duchess of Brabant|Marie of France]], a daughter of Philip II and [[Agnes of Andechs-Merania]].{{sfn|McDougall|2017|p=226}}

After his return to France, and with the support of Philip II, Arthur embarked on a campaign in Normandy against John in 1202. Poitou revolted in support of Arthur. The Duke of Brittany besieged his grandmother, [[Eleanor of Aquitaine]], John's mother, in the Château de Mirebeau. John marched on [[Mirebeau]], taking Arthur by surprise on 31 July 1202.{{sfn|Seel|2012|p=47}} Arthur was captured by John's barons on 1 August, and imprisoned in the [[Château de Falaise]] in [[Falaise, Calvados|Falaise]], Normandy.