Fortified Sector of the Dauphiné

The Fortified Sector of the Dauphiné (Secteur Fortifié du Dauphiné) was the French military organization that in 1940 controlled the section of the Alpine Line portion of the Maginot Line facing Italy in the vicinity of Briançon. By comparison with the integrated defenses of the main Maginot Line, or even of the Fortified Sector of the Maritime Alps to the south, the Dauphiné sector consisted of a series of distinct territories that covered two main invasion routes into France: the route from Turin over the Col de Montgenèvre to Briançon and Grenoble, and the route from Coni over the Col de Larche to Barcelonette and Gap. The sector was the scene of probing attacks by Italian forces during the Italian invasion of France in 1940, in which the French defenses successfully resisted Italian advances until the June 1940 armistice that granted Italy access to southeastern France.

The sector was extensively subdivided into informal districts, sub-sectors and quarters or quartiers, reflecting the fragmented nature of the Alpine landscape in which each valley was a distinct defensive entity. Small units were employed to patrol the border and to man individual posts ranging from observation bunkers to excavated mountaintop artillery ouvrages.

The area around Briançon and the Ubaye Valley had already been extensively fortified by Vauban and Raymond Adolphe Séré de Rivières, culminating in the enormous Fort de Tournoux. The Italian Fort Chaberton presented a menace to the area with its heavy battery on a commanding 3,131-metre (10,272 ft) peak just across the border, 11.6 kilometres (7.2 mi) from Briançon. Measures were proposed in 1929 to counteract the threat by building four large ouvrages at Gondran, les Aittes, Janus and les Alberts. These major Alpine positions were to be built by the Commission pour l'Organisation des Régions Fortifiées (CORF), the primary organization dedicated to the planning and funding of the Maginot Line. Resources were soon diverted into fortifications for the SF Alpes-Maritimes to the south, and initial improvements were limited to a reconstruction of the old Fort du Janus.

...
Wikipedia