Defensive Sector of the Rhône

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.

The SD Rhône was largely ignored until 1939, when a belated program was initiated to deal with a potential invasion through Swiss territory.

A 1938 revision scaled the proposal back, replacing ouvrage Crêt Mourex with a fortified position at the bottom of the Col de la Faucille, along with five blockhouses at Crêt Mourex, Riamont, Le Pailly, Petit-Montrond and Montets, and a demountable turret at Arbère.

[4] The Chablais sub-sector covered the territory around Lac Léman with a series of blockhouses defending strategic routes.

In early June the 230th DBAF (a demi-brigade of five battalions) was placed to block the German advance along a front between Frangy and Annecy.

The Fort l'Écluse blocked the German advance toward Albertville, manned by a company of the 179th Alpine Fortress Battalion along with personnel from several miscellaneous units of artillery and regional reserve forces.

The standoff continued until 30 June, when General Charles Huntziger, in charge of post-surrender French forces, ordered the unit to permit passage to the Germans, and to surrender.

[5] The Fort l'Écluse was purchased by a syndicate of nineteen communities of the Pays de Gex and is operated as a museum.