Alpine Line The Alpine Line ( ) or Little Maginot Line ( French : " Petite Ligne Maginot " ) was the component of the Maginot Line that defended the southeastern portion of France . In contrast to the main line in the northeastern portion of France , the Alpine Line traversed a mountainous region of the Maritime Alps , the Cottian Alps and the Graian Alps , with relatively few passes suitable for invading armies . Access was difficult for construction and for the Alpine Line garrisons . Consequently , fortifications were smaller in scale than the fortifications of the main Line . The Alpine Line mounted few anti - tank weapons , since the terrain was mostly unsuitable for the use of tanks . Ouvrage Rimplas was the first Maginot fortification to be completed on any portion of the Maginot Line , in 1928 . The Alpine Line was unsuccessfully attacked by Italian forces during the Italian invasion of France in 1940 . Following World War II , some of the larger positions of the Alpine Line were retained in use through the Cold War . Concept . As France studied measures to protect its northeastern frontier with Germany , a parallel effort was made to examine the improvement of France ' s defenses against Italy in the southeast . France ' s Italian border was a relic of the 1860 Treaty of Turin in which the Duchy of Savoy and the County of Nice were incorporated into France . The treaty boundary roughly followed the crest of the Maritime Alps inland through the Cottian Alps to Switzerland . The precise line of demarcation left the upper reaches of many westward - draining valleys in Italian hands , thus giving Italy positions on high points overlooking French territory , most notably Fort Chaberton on Mont Chaberton , which threatened Briançon . The region had been extensively fortified in the seventeenth , eighteenth and nineteenth centuries , most notably by Vauban , whose fortifications of Briançon have been designated a UNESCO World Heritage Site , and by Raymond Adolphe Séré de Rivières in the late nineteenth century , who expanded the Fort de Tournoux and other fortifications in the area as part of the Séré de Rivières system of fortifications . Passage through the Alps was possible only at a series of comparatively low passes , and movement toward the major cities of southeastern France such as Lyon , Grenoble or Nice was possible only along a series of deep river valleys . Defenses therefore tended to concentrate in consistent locations : In 1925 General Charles Nollet , the Minister of War , directed General Jean Degoutte to survey the southeastern frontier and to make recommendations for their defense . Degoutte ' s proposal used principles of defense in depth to economize on manpower and funds , which were needed for the main Maginot defenses in northeastern France . The still - ambitious plan proposed in 1927 envisioned a series of fortified positions right on the frontier divides at every potential crossing , backed by thirty - six centers of resistance , each with fourteen infantry casemates and twelve infantry shelters , a total of about one thousand blockhouses . Costs were estimated at 250 million francs . The proposed plan was criticized for placing the fortifications too far forward by the " Commission de Defense " , but the overall organization was approved by Minister of War ( and former Prime Minister ) Paul Painlevé , with a strategy of fortifying Menton , Sospel and the valleys of the Vésubie and Tinée . Revisions in late 1927 proposed about 400 positions at a cost of between 400 million and 500 million francs . The plan was altered in 1928 by General Fillonneau , who proposed to concentrate fortifications along potential invasion axes , rather than along a continuous line . The geographic emphasis remained on Menton and Sospel , but the concept of frontal confrontation was replaced by a strategy of attack from the flanks of a potential advance . Fillonneau was assisted by the new management organization for the Maginot fortifications , the " Commission d ' Organisation des Régions Fortifiés " , or CORF . The proposal was estimated to cost 700 million francs to build 103 " ouvrages " and to reconstruct 28 old fortifications . An initial phase , designed to protect Nice , was estimated to cost 205 million francs Unlike the relatively thin , linear defenses of the northeast , the revised Alpine fortifications extended some distance back from the frontier , with forward defenses supported by rearward defenses , compartmentalized by the terrain into distinct sectors . A final proposal in 1930 established a scaled - back , prioritized programme of 362 million francs to be executed in two phases , with the second phase to cost an additional 62 million francs . Description . As with the main Maginot Line of the northeast , positions took the form of concrete - encased strongpoints linked by underground tunnels , which housed living quarters , magazines and utilities for the " ouvrage " . Larger " ouvrages " were provided with 60 cm - gauge rail lines to move materials and munitions , although unlike the northeastern positions , none were electrified . Because of the mountainous terrain and the vertical character of the sites chosen for fortification , individual blocks typically emerged from rock faces in a steep hillside or cliff with mined galleries within under rock cover . By comparison , most northeastern " ouvrages " were semi - submerged into the gently rolling soil with galleries deeply buried beneath earth cover . Many of the high - altitude " petits ouvrages " could only be built during the brief Alpine summer , leading to extended construction schedules , and causing many of these high outposts to be uncompleted at the outbreak of war in 1940 . In addition to the linked complexes of blockhouses that formed the grand and petit ouvrages , the country around and between each position was provided with isolated blockhouses , observation points , shelters ( or " abris " ) , outposts ( " avants postes " ) and batteries , using much the same vocabulary of rounded concrete forms as the primary line of fortifications . These positions allowed the use of mobile supporting artillery , and provided rallying and control points for the necessary infantry support in the country between strongpoints , as the security of the border did not and could not depend on subterranean fortifications alone . The disposition of forward outposts , backed by heavier fortifications some kilometers to the rear , provided a defense in depth that was , in the case of the Alpine fortifications , supported by the difficult terrain . Organization . The Alpine Line was divided into three major sectors . From north to south , they were : In addition , the area to the north of the principal fortifications was organized as the Defensive Sector of the Rhône , with virtually no fixed fortifications , since it faced neutral Switzerland . The Alpine region was under the overall command of the Army of the Alps , General René Olry in command at Valence . Its chief units were the 14th Army Corps in the SF Savoy and SF Dauphiné , and the 15th Corps in the SF Maritime Alps . Construction . Work had already begun on Ouvrage Rimplas , which was in fact the first Maginot " ouvrage " to be built in either the northeast or southeast . The construction contract was signed 7 September 1928 with incomplete plans . Rimplas was a prototype project , not representative of other alpine or Maginot positions . CORF took over responsibility for construction in 1931 , standardizing design practices , although each project was closely adapted to local circumstances . Construction was made difficult by poor access , high altitude and a short construction season . In 1931 work commenced at twenty - two sites . In 1932 Ouvrage Cap Martin was sufficiently complete that it could be used in an emergency . Work continued through 1936 , even though CORF had been disestablished at the end of 1935 . While most of the larger positions were complete , a number of the smaller , higher - altitude positions were never completed in time for war in 1940 . From 1937 , the " main d ' oeuvre Militaire " ( MOM ) built a number of light positions and blockhouses , usually in locations close to the frontier . Many of the MOM positions were incomplete in 1940 . Compared with the northeastern Maginot positions , the Alpine fortifications made comparatively little use of retracting turrets , using instead concreted casemates in mountainsides surveying prepared fields of fire . The Alpine Line featured relatively few artillery " ouvrages " , tending instead to use mixed - arms positions that combined artillery casemates and infantry positions . The main fortifications were supported by infantry shelters , or " abris " , of both the " passive " , lightly armed type , and " active " " abris " with heavier armament . Some of the mountaintop " gros ouvrages " used aerial tramways for their primary means of access . Military roads were often constructed in the absence of existing access . All of the large positions were provided with subterranean barracks and central utility plants . Nearly all fortifications were excavated from solid rock . Coverage could therefore be reduced compared to the " ouvrages " of the northeast , which were at depths of up to in deep soil to resist heavy siege artillery . Independent means of power generation were a necessity in the absence of a utility distribution system . Likewise , telephone communication was problematic , with many positions using line - of - sight optical semaphores for communication . June 1940 . Like the main Maginot Line did with the Germans , the Alpine Line achieved the goal of preventing the Italians from advancing through the protected areas . And , as the Italians had no alternative but to directly confront the fortifications the south of France , was completely protected from the Italian advance . An advance along the main coastal road was delayed by stiff resistance at the Casemate du Pont Saint Louis on the border at Menton , which was manned by seven men led by a non - commissioned officer and was supported by main - line fortifications at Ouvrage Cap Martin . A direct assault on Cap Saint Martin was suppressed by the " ouvrage " itself , supported by artillery fire from Ouvrage Mont Agel Two more attacks were mounted , in the areas of Briançon and the Little St Bernard Pass , with little effect due to weather and the difficult terrain . Positions in the high Alps were shelled by Italian forces but were not directly attacked . Ouvrage Barbonnet traded fire with Italian positions prior to the armistice of 25 June 1940 . " Vallo Alpino " . The Italian counterpart to the Alpine Line was Italy ' s Alpine Wall ( " Vallo Alpino " ) , the western portions of which faced the Alpine Line across the Alpine Valleys .