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 " . Concept and organization . 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 peak just across the border , 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 . Other funds were provided to create border posts ( " avants - postes " ) close to the frontier . These projects were administered by the Military Works Administration ( " Main d ' Ouevre Militaire ( MOM ) " ) , which built more economical but less secure and less strongly - armed versions of the CORF works . MOM " avants - postes " superficially resembled CORF " ouvrages " , with underground gallery systems linking individual combat blocks , but lacked heavy armament and thick concrete shielding , as well as independent ( or any ) electric power supplies and underground troop accommodations . A number of the later CORF - proposed " ouvrages " were carried out by MOM , many of which were incomplete in 1940 . These MOM - built positions covered secondary passes and mountain basins . The Col de Larche corridor was defended by the CORF - built " gros ouvrage " Roche - la - Croix , its upper battery and the Forts Tournoux and Viraysse , as well as a variety of CORF positions around Saint - Ours . The Montgenèvre corridor was covered by the extensive network of forts around Briançon , centering on the renovated and expanded fortifications at Janus . The Col de la Bonette received attention as well , despite its altitude , with the " gros ouvrage " Restefond and three subsidiary " petits ouvrages " . Troop units for these fortifications were extensively customized to deal with the fragmented nature of the military positions . Typical , somewhat confusingly - named units included : These formations were supplemented by Position Artillery Regiments ( " Régiments d ' Artillerie de Position " ) ( RAP ) ) , which provided mobile artillery support . A demi - brigade was similar to a large regiment , with three demi - brigades equivalent to four regiments . Command . The Dauphiné sector was under the overall command of the French Army of the Alps , headquartered at Valence , under the command of General René Olry . Subordinate to the Army of the Alps was the 14th Army Corps under General Beynet . The SF Dauphiné itself was commanded by General Cyvoct at Gap and La - Roche - de - Rame . The interval troops , the army formation that was to provide the mobile defense for the sector , to support and be supported by the fixed defenses , was the 64th Infantry Division . Artillery support for the sector was provided by the 154th and 162nd Position Artillery Regiments ( " Régiment d ' Artillerie de Position ( RAP ) " ) , which controlled both fixed and mobile artillery , commanded by Lt . Colonel Maury and Chef d ' Escadron Jarrix , respectively . The 64th ID was made up of Class B reservists , not suited for sustained combat , under General de Saint - Vincent at Embrun . Description . The sector includes , in order from west to east , the following major fortified positions , together with the most significant casemates and infantry shelters in each sub - sector : Briançonnais district . The direct command of the Briançon valley remained with General Cyvoct , with a command post at La Roche - du - Rame , and a forward command post at the Fort du Randouillet . Sub - sector Haute - Clarée - Guisane . 82nd Alpine Fortress Battalion ( " 82 Bataillon Alpin de Forteresse ( BAF ) " ) , Lt . Colonel Perdreau , command post at the Bois du Villar Quartier Chardonnet . Command post at Chardonnet , elements of the 24th BIL Quartier Bufère - Granon . Command post at the Col de Cristol , elements of the 82nd BAF Quartier Peyrolles . Command post at the Bois du Villar , 95th Alpine Cavalry Battalion ( " 95 Bataillon des Chasseurs Alpins ( BCA ) " ) Sub - sector Haute Durance - Cerveyrette . 72nd Alpine Fortress Bataliion ( " 72 Bataillon Alpin de Forteresse ( BAF ) " ) , Lt . Colonel Brasset , in charge of the defense of Briançon , command post at Randouillet . Quartier Vachette - Janus . Command post at La Lame , 91st Alpine Cavalry Battalion ( " 91 Bataillon des Chasseurs Alpins ( BCA ) " ) Ouvrage la Vachette was started 20 March 1940 , no substantial progress made before war broke out . A stop line of about 25 smaller fortifications was constructed in the area . These fortifications have been cleaned up and may be visited . Quartier Gondran - Aittes . Command post at La Seyte , elements of the 72nd BAF Barracks for peacetime : A number of concrete emplacements were built by the " Main d ' Oeuvre Militaire ( MOM ) " in the quarter . Vallée du Queyras region . The Queyras valley was commanded by Lt . Colonel Bonnet of the 45th DBCA , with a command post at Guillestre , and a forward command post at Villargaudin . Sub - sector Guil . 45th Alpine Cavalry Demi - Brigade ( " 45e Demi - Brigade des Chasseurs Alpins ( DBCA ) " ) , Lt . Colonel Martin , command post at the Villargaudin . Quartier Péas . No fixed positions , 107th Alpine Cavalry Battalion ( " 107 Bataillon des Chasseurs Alpins ( BCA ) " ) , command post at Fort Queyras . Quartier Queyras . No fixed positions , 87th Alpine Cavalry Battalion ( " 87 Bataillon des Chasseurs Alpins ( BCA ) " ) and elements of the 92nd BAF , command post at La Motte Tremblante . Quartier Sommet - Bucher . Five small " avants postes " , manned by the 1st and 3rd companies of the 92nd BAF and a company of the 87th BCA . , command post at Sommet - Bucher . Quartier Ceillac . 102nd Alpine Fortress Battalion ( " 102 Bataillon Alpin de Forterresse ( BAF ) " ) , command post at the Col de Bramousse . A number of concrete emplacements were built by the MOM in the quarter . Vallée de l ' Ubaye district . Colonel Dessaux , command post at either Jausiers or Batterie XII at Tournoux . Sub - sector / Ubaye - Ubayette . 83rd Alpine Fortress Battalion ( " 83 Bataillon Alpin de Forterresse ( BAF ) " ) , command post at the Fort Moyen at Tournoux . Quartier Saint - Paul . Command post at Grande = Serrenne Sub - sector Jausiers . 157th Alpine Fortress Demi - Brigade ( " 157e Demi - Brigade Alpin de Forteresse ( DBAF ) " ) and 73rd BAF Quartier Sagnes . First company of the 73rd BAF . Ouvrage des Sagnes was proposed but not built . Quartier Restefond . Second company of the 73rd BAF . Quartier Rougna . Additionally , 36 concrete shelters were built by MOM in 1939 in the area . History . When Italy declared war on France on 10 June 1940 , the French forces along the Alpine Line amounted to two corps constituting the Army of the Alps . They faced two poorly equipped Italian armies , the 1st and 4th . The northern portion of the SF Dauphiné around Briançon was held by elements of the French XVI Corps , while the southern , Ubaye district was held by XIV Corps . These formations faced the Italian Fourth Army . Italian invasion of France . Actions in the Briançon area were focused on the threat posed by the mountaintop batteries at the Italian Fort Chaberton , armed with eight 149mm guns in turrets . On 17 June 1940 , Chaberton opened fire on the Fort de l ' Olive , with little effect . The next day , infantry pressure was applied around the Cleyda blockhouse , and fire was exchanged between Italian batteries and " ouvrage " Janus . By the 20th , Italian forces of the " Assietta " Division were infiltrating around Montgenèvre and Chaberton was firing on Janus , Gondran , les Aittes and Infernet , cutting electricity to Janus . Janus operated on local power while a battery of 280mm mortars of the 154th Position Artillery Regiment ( " 154 Régiment d ' Artillerie de Position " ) was set up in two locations near Gondran and Infernet . Several columns of Italian infantry made probing attacks in the vicinity of Cerveyrette . On the 21st , Chaberton fired on Janus and Gondran , firing about 900 shells at Janus alone , causing moderate damage to the surface installations . However , the French mortar batteries were by this time in place . Fire from the heavy mortars damaged five of the eight Italian guns of Chaberton . The next day was relatively quiet , apart from some infantry infiltration by the Italian " Sforzesca " Division near the base of the Janus massif . Skirmishing took place on the 23rd , when the Italians captured the " avant - poste " Est du Chenaillet . Chaberton began firing again , receiving counter - battery fire from the French batteries in reply . The exchange continued the next day , and stopped only when the armistice took effect on the 25th , with six of eight Italian gun positions destroyed . Farther south in the Queyras , the Italian " Julia " Division mounted weak probes without much success . In the Ubaye , the Italian 2nd Army Corps ( " 2 Corpo d ' Armata " ) under General Bertini sought to move across the Col de Larche in Operation M ( named for the Italian name of the pass , " Colle della Maddalena " ) . The corps was composed of five divisions : the 2nd Alpine Group ( " Raggrupamento Varaita - Po " ) , and the " Cuneense " , " Forli " , " Pusteria " and " Livorno " Divisions . The principal activity took place , as expected , in the vicinity of the Col de Larche , starting on 17 June with infantry patrols that were engaged by the artillery of Roche - la - Croix , producing heavy Italian casualties . On the 20th the Observatoire de Viraysse was heavily bombarded , prompting retaliatory fire from Roche - la - Croix against Italian observation positions . The next day a strong column of Italians of the " Acqui " Division moving across the Col de Sautron and the Col des Monges to the Fort de Viraysse were turned back by field artillery fire . On the 22nd Italian artillery again concentrated on the Observatoire de Viraysse and the " avant - post " de Larche , again answered by Roche - la - Croix ' s 75mm gun turret . Other batteries took on a new advance over the Col des Monges . The Fort de Viraysse was encircled . Snow fell on the 23rd , but late that day the Italians launched an unsuccessful assault on the Fort de Viraysse . The bad weather continued on the 24th , but a sharp engagement on the Col Rémi and around Tête - Dure resulted in heavy Italian casualties and a number of prisoners . The area around the Col de Restefond was subject to heavy snow , and had been unoccupied from October 1939 to mid - May 1940 , when enough snow had cleared to allow the positions to be used and occupied . Apart from some skirmishing and artillery barrages , more decisive action was hampered by bad weather . Action in all areas stopped when the armistice took effect on 25 June . The Italians had failed to accomplish any significant penetration of the frontier , but German forces had come down the valley of the Rhône and were operating to the rear of the Alpine Line . Under the terms of the armistice , the frontier became a demilitarized zone , at least as far as French forces were concerned , deep . It was nominally occupied by Italian forces , but the French forces had surrendered to the Germans . Units . The 72nd Alpine Fortress Battalion was , on mobilization in 1939 , the source of the 82nd , 92nd and 102nd BAFs , as the battalion ' s four companies grew in size . The battalion was stationed at Briançon at the Fort du Randouillet and the Fort de Queyras . After mobilization the reorganized battalion held the Gondran - Aittes quarter , occupying " ouvrages " Janus , Gondran and Les Aittes . Interval troops held the crest of the Gondran massif and the road at Clôt Enjaime . In May 1940 the battalion took up its positions as soon as high - altitude snows permitted . The battalion saw action on 23 June against the Italian 30th Infantry Regiment at the " avant - poste " Chenaillet , losing 19 captured in foggy conditions . After the June 25 armistice the 72nd returned to Briançon , then moved on to the southeast of Gap , where it was dissolved on 31 July . Active - duty personnel were incorporated into the Vichy French " bataillon départmental des Hautes - Alpes at Gap and a guard unit at Briançon . 1944 . During the Occupation , the completed " ouvrages " had been provided with caretakers and were kept in good condition . With the Normandy landings , the French Resistance was instructed to impede German reinforcements from reaching northwest France by sabotaging the choke points through the Alps . The Petit Saint - Bernard , the Mont - Cenis and the Col de Larche were to be blocked . On 15 August 1944 , the Operation Dragoon landings were accomplished by the Allies against light opposition . Briançon , which had been occupied by the German 5th " Gebirgsjäger " Division , was evacuated on 24 August and occupied by Resistance forces . However , the Germans remained in the surrounding fortresses , and the 90th Panzergrenadier Division mounted an unsuccessful counterattack against American patrols and French forces , operating from the Fort du Randouillet . The newly arrived 4th RTM and 3rd Moroccan under Colonel Molle mounted an offensive to drive the Germans over the Col du Montgenèvre starting on 4 September , and taking Gondran , Infernet , Croix - de - Bretagne , Chenaillet and Janus the same day . Randouillet and the Fort des Têtes were captiured on the 6th , but German forces on the crest of the Col du Montgenèvre continued to fire into Briançon . The area around Les Fourches and Restfond was captured by French and American forces in late September , but was evacuated for the winter in October . The reactivated Fort Chaberton continued to fire on Briançon until it was captured in April 1945 . Roche - la - Croix was captured by a new offensive on 22 April 1945 . The next day Saint - Ours Haut and Bas were captured . Post - War . As part of the Paris Peace Treaties of 1947 , the Franco - Italian border was adjusted to place Mont Chaberton and the upper reaches of the Col du Larche in France . Nevertheless , the major Alpine positions remained operational , preserved until the 1970s when interest in expensive fixed fortifications had declined . Present status . Both Saint - Ours Haut and Saint - Ours Bas have been preserved and are available for tours by the public . Ouvrage Janus is owned by the Commune of Montgenèvre , and is being considered for public access . Many of the high - altitude positions are open to the elements . The Vauban and Séré de Rivières - era fortifications around Briançon have been preserved , or remain military installations . The Vauban fortifications of Briançon have been designated Unesco World Heritage Site s .