Alpine Line - Concept

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:

• Bourg-Saint-Maurice in the Tarentaise, facing the Little St Bernard Pass
• Modane in the Maurienne, facing the Mont Cenis pass
• Briançon, facing the Col de Montgenèvre
• Barcelonnette, facing the Col de Larche
• Approaches to Nice from the north, with defenses in the Tinée and Vesubie valleys, around Sospel and on the Authion massif
• Menton and Nice, guarding the coastal road and railway line

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.