Isabella's husband Edward, as the Duke of Aquitaine, owed homage to the King of France for his lands in Gascony. Isabella's three brothers each had only short reigns, and Edward had successfully avoided paying homage to Louis X, and had paid homage to Philip V only under great pressure. Once Charles IV took up the throne, Edward had attempted to avoid doing so again, increasing tensions between the two. One of the elements in the disputes was the border province of Agenais, part of Gascony and in turn part of Aquitaine. Tensions had risen in November 1323 after the construction of a bastide, a type of fortified town, in Saint-Sardos, part of the Agenais, by a French vassal. Gascon forces destroyed the bastide, and in turn Charles attacked the English-held Montpezat: the assault was unsuccessful, but in the subsequent War of Saint-Sardos Isabella's uncle, Charles of Valois, successfully wrested Aquitaine from English control; by 1324, Charles had declared Edward's lands forfeit and had occupied the whole of Aquitaine apart from the coastal areas.