How did Philip IV take control of Gascony from Edward I?

Philip IV of France took control of Gascony from Edward I by leveraging his position as suzerain to intervene in the duchy's affairs and exploiting maritime conflicts.1

The crisis began in 1293 following a series of skirmishes between English and Bayonne ships and a Norman fleet. Philip IV demanded compensation and, when the dispute remained unresolved, announced the confiscation of the duchy of Guyenne (which included Gascony) on May 19, 1294.12

Following this declaration, Philip IV’s forces—led by his brother, Charles of Valois, and his cousin, Robert II of Artois—launched successful military campaigns in the region. By 1296, Philip had become the effective master of almost the entire duchy. While Edward I attempted to retaliate by forming an alliance with Guy of Dampierre, the count of Flanders, the conflict eventually concluded with a truce in 1297, later confirmed through the arbitration of Pope Boniface VIII.1