The Defensive Sector of the Rhône (Secteur Défensif du Rhône) was the French military organization that in 1940 controlled the section of the French border with Switzerland and Italy in the area of Geneva. The area was not regarded as a likely point of invasion, owing to the neutrality of Switzerland and the extremely difficult terrain along the Italian portion of the border. It was therefore lightly fortified. Its chief fortified position was the 19th-century Fort l'Écluse, manned by a small force, which held its strategic position against a Panzerkorps for a week in June 1940.