Treaty: Le Goulet, 1200

The Capetians and the Plantagenets were in an almost constant state of war during the time of the Angevin Empire of 1154-1214, and of course the issue was land.  While the Plantagenet kings held dominion over almost half of what makes up modern day France, they were in theory under the Capets as their overlords.  Try telling that to Henry II, Richard I or John, who didn't believe they were beholden to anybody.  The various English and French kings involved during this period made several treaties, and just as soon broke them.  The treaty between John and Phillip II Augustus of France in 1200 was just another piece of paper.

The treaty's name comes from Gueleton Island in the Seine River near Vernon, Normandy.  It called on Phillip to recognize John as King of England, even though John's teenage nephew, Arthur Duke of Brittany had the more senior claim as the son of Geoffrey, the brother between John and Richard in birth order.  John had to recognize Phillip as his overlord for all the Plantagenet holdings on the Continent including most of Normandy, and recognize that Phillip, not John, was the overlord of the Counts of Boulogne and Flanders.  John also agreed not to support any rebellion undertaken by the two counts aforementioned.  Phillip demanded 20,000 marks of silver to allow John to keep suzerainty of Brittany, and thus Arthur, and to keep the Plantagenet family's home province of Anjou under his own domain. 

Because Eleanor of Aquitaine was still alive and neither King wanted to cross her up, Aquitaine and Poitou were left out of the equation.  John's niece Blanche of Castile, from his sister Eleanor, was married to Phillip's son Louis to seal the treaty.  Despite the marriage, the treaty blew up within two years.  In 1202, John refused to answer a summons to appear before Phillip to answer charges that John was once again intriguing with some of Phillip's vassals for rebellion.  Phillip declared John dispossessed of his ancestral lands and invaded Normandy.  John rallied an army to deal with the threat, the first of many costly endeavors which would see England lose Normandy, Anjou, Maine and Touraine by 1214.  So much for treaties.