How did the dispute over Gascony contribute to the Hundred Years’ War?

The dispute over Gascony was a fundamental cause of the Hundred Years’ War, rooted in the Treaty of Paris of 1259. This treaty established an awkward relationship where the kings of England held Gascony as vassals to the French crown, requiring them to pay homage to the French king.2

This arrangement created persistent friction for several reasons:

• French Intervention: French royal officials frequently intervened in the duchy’s affairs, encouraging local malcontents to appeal against their English duke to the Parlement of Paris.1
• Territorial Disputes: Both sides built fortified towns, known as bastides, which led to ongoing conflict. Additionally, there were frequent disputes over the restoration of lands and acts of piracy by English and French sailors.2
• Confiscation: Tensions escalated when French kings repeatedly declared the duchy forfeit, such as in 1294 and 1324, leading to military occupations.1

By 1337, Edward III sought to recover lost Gascon lands and resented French support for the Scots. When Philip VI declared Gascony confiscated in May 1337, it served as a primary catalyst for the outbreak of the war.32