Fortress Saint - Maurice Fortress Saint - Maurice is one of the three main fortification complexes comprising the Swiss National Redoubt . The westernmost of the three , Fortress Saint - Maurice complements Fortress Saint Gotthard and Fortress Sargans to secure the central alpine region of Switzerland against an invading force . The National Redoubt was first conceived in the 1880s as an easily defensible area to secure the survival of the Swiss Confederation . In the late 1930s and 1940s when neutral Switzerland was threatened with invasion from Germany , the National Redoubt and its components were modernized and expanded on a massive scale . The fortification system was maintained and upgraded during the Cold War . With the collapse of the Soviet Union , the possibility of a Warsaw Pact invasion disappeared , and by 1995 many positions were abandoned by the military . Fortress Saint - Maurice encompasses the area around Saint - Maurice in the western , French - speaking portion of Switzerland . The Rhône river leaves the central Alpine region at Saint - Maurice through a narrow defile , between 4000m mountains to the south and 3000m mountains to the north . The only comparatively easy access to the upper Rhône valley , and thus to the western National Redoubt , is through Saint - Maurice . Fortress Saint - Maurice is a series of fortifications set into the mountains on either side of the valley , dominating the region as far as Lac Léman with their artillery . The principal fortification is the enormous Fort de Dailly , supported by forts Savartan , Scex and Cindey , as well as lesser positions . The extent of the area designated as Fortress Saint - Maurice is not clearly defined , but according to the Association Fort de Litroz , the Saint - Maurice sector comprises the Rhône narrows from just north of Saint - Maurice to Martigny , excluding Chillon and Champillon , as well as the fortifications of the lateral valleys . Concept and organization . Fortress Saint - Maurice is not a single , connected fortified position , but rather a series of mutually supporting self - sufficient fortifications that dominate the Rhône valley between Saint - Maurice and Martigny . The Rhône in this area runs through a deep valley with the classic U - shaped glacial profile . These steep cliff walls , framing a flat valley floor averaging about wide , create a natural gauntlet . The individual forts are mined as galleries running in the valley walls overlooking the valley and each other . The higher - level forts are accessed by aerial cableway s or by inclined funicular s mined within the mountains . Fortress Saint - Maurice bars an enemy moving from France into the central Alps , and to a lesser extent , prevents an enemy crossing the Great Saint Bernard Pass or the Simplon Pass from moving against Lausanne . The Saint - Maurice fortifications were supported by additional positions in advance of the main strongpoint , with major forts at Chillon and Champillon , as well as additional fortifications in side valleys and lesser thoroughfares . While the Saint - Maurice area has been fortified since medieval times , work on the National Redoubt began in the 1880s with Forts Dailly , Savatan and Scex . World War II and the prospect of invasion by Germany and possibly Italy gave new impetus to the fortification program , causing existing fortifications to be updated and new fortifications to be constructed . In particular , Fort de Dailly became one of the largest and most heavily armed fortifications in Switzerland . Virtually every constriction , bridge , tunnel or other defensible position in the valley was fortified with blockhouses , anti - tank barriers , permanent minefields or pre - surveyed artillery coverage . Industrial facilities , such as the Vezey hydroelectric plant , incorporated fortifications into their construction . All construction was carefully camouflaged using light shells to simulate rock formations , or with a house - shaped superstructure . The fortifications were maintained and progressively upgraded through the close of the Cold War . By 1995 , many were deactivated . The Saint - Maurice fortifications are considered potential historic monuments and have remained in relatively good repair . Principal fortifications . The Saint - Maurice fortifications are disposed in mutually supporting groups , often with pairs of forts that provide mutual support by direct fire as well as supporting more distant parts of the ensemble by means of indirect fire . From north to south , the principal components are as follows : North of Saint - Maurice . Fort de Toveyeres is an infantry fort built to cover the eastern end of the Lavey anti - tank barrier . The barrier , made up of dragon ' s teeth and a deep ditch , spans the Rhône valley north of Saint - Maurice . The Courset stream runs in the ditch . The tailwater stream from the Lavey hydroelectric station affords an additional barrier , while the power station is itself fortified , with covering fire from the Fort de Cindey . Fort du Petit - Mont is just to the north of Toveyres , providing more cover to the Lavey barrier . Galerie du Scex and Cindey . The Scex and Cindey fortifications are built into the dramatic Scex escarpment overlooking Saint - Maurice . These two forts , opposite the earlier Savatan and Dailly forts , completed the major portion of the Fortress Saint - Maurice ensemble in the early 20th century . Scex is primarily an artillery fort , which Cindey is a mixed artillery and infantry position . The forts , together with the Grotte aux Fées natural cave , are open to public tours . Fort du Scex ( A166 ) comprises part of a fortress complex encased in rock high above the strategic Saint Maurice valley . Scex is connected to Cindey by the natural caves of the Grotte aux Fées . The fort was planned to provide supporting fire to the larger and earlier forts Savatan and Dailly on the right bank of the Rhône . The Galerie du Scex was initially armed with four 75mm guns in 1911 . From 1915 it was expanded . The connection to the Grotte aux Fées was built in 1935 - 36 . The Ermitage battery of four 75mm guns was constructed in 1938 - 39 , with further improvements to habitation during and after World War II . The artillery was deactivated in 1984 , when the position was converted to use as a command post . By 1995 the fort was entirely deactivated . Routine access to the fort for supplies was provided by an aerial cableway . Fort de Cindey ( A155 ) was built between 1941 and 1946 and expanded between 1948 and 1952 . Located in rock galleries in a northern continuation of the Scex cliff , the fort controlled the narrow defile of the Rhône river . The fort was initially armed with two 105mm guns , with four 90mm anti - tank guns and three machine guns added in the 1950s , part of the program begun at Dailly . The fort served until 1995 , when it was taken out of service . Power and communications were supplied by Fort de Scex . Supplies were provided by an aerial ropeway similar to that of Scex . Savatan - Dailly . The forts at Savatan and Dailly were completed in 1894 and became the central elements of Fortress Saint - Maurice . They were progressively expanded and upgraded through the twentieth century . Fort de Dailly ( A250 ) is one of the largest and most heavily armed forts in Switzerland , and the central position in Fortress Saint - Maurice . The artillery fort is located on the end of the Dailly massif at a higher level than Savatan . Work began at Dailly in 1892 . The entrance to the underground fort lies at at the end of 29 switchbacks . The fort initially was armed with six 120mm gun turrets with additional open artillery positions . Two 75mm guns were mounted in casemates , while portable 53mm gun turrets occupied prepared surface positions . Dailly was upgraded with 105mm artillery during the 1940s , with as many as ten 105mm guns in casemate positions . Dailly was the scene of an ammunition explosion on 28 May 1946 , when about 5500 105mm shells , amounting to 449 tons , exploded in three separate magazines successively . The blast threw four 105mm guns from their emplacements and damaged six more . Six construction workers were killed , part of a crew working on a funicular shaft linking Dailly to the upper part of Savatan . The explosion was attributed to decomposition of nitrocellulose propellant . Two similar explosions happened at Grisons in June 1946 and at Blausee - Mitholz in 1947 , without loss of life . The damage to Dailly resulted in a comprehensive modernization of the fort , with additions of 81mm and 120mm mortars , removal of obsolete weapons and the installation of two modern 155mm gun turrets . An underground caserne for 650 men was built at this time , with NBC protection . The four 105mm guns of the northern casemates and the two 105mm guns of the central casemate were repaired and upgraded , but the four guns of the south battery were never replaced . The new 155mm gun turrets were mounted on barbettes deep , with an individual rate of fire of 30 rounds per minute in bursts , or 15 rounds per minute sustained . Design began in 1949 , with the first test firings in 1960 . Dailly was deactivated in 1995 and decommissioned in 2003 . With the other Saint - Maurice fortifications , it has been designated as a candidate for preservation , but is not open to the public . Fort de Savatan ( A200 ) occupies a shelf on the northwest side of the Dailly massif on the eastern side of the Rhône valley , overlooking Saint - Maurice to the northwest . With up to 1600 troops , the artillery fort mounted five turrets for 120mm guns , a number of 53mm gun turrets and four 84mm guns in caponiers for close defense . Savatan was upgraded at the same time as Dailly , adding an NBC - protected 350 - man underground caserne . South of Saint - Maurice . Fort d ' Evionnaz ( A80 ) is an infantry fort in rock - cut galleries , designed to support the anti - tank line between Evionnaz and Collognes . The position was garrisoned by an infantry company and extends over four levels . The fort flanks the west side of the " dragon ' s teeth " anti - tank line that spans the flat floor of the valley . As constructed in 1939 , Evionnaz was armed with 47mm anti - tank guns and machine guns . These were upgraded in the 1970s to 90mm guns and improved machine guns . The anti - tank line was planned principally to block an advance from the south toward Lac Léman , rather than the other way around , as most of the area ' s fortifications were planned . Martigny area . Fort Follatères ( A66 ) is located near Martigny on the north side of the Rhône , and a point where the river bend at a right angle and joins the Drance . Follatères was armed with four 75mm guns covering Martigny and two 105mm guns aimed in the direction of the Great Saint Bernard Pass . Fort de Vernayaz ( A68 / 69 ) complements Follatères on the south side of the Rhône at Vernayaz . The fort occupies a unique location at the mouth of the Trient Gorges overlooking the rail line and Verayaz . The fort is accessed by walkways on the cliffside above the torrent , with footbridges connecting tunnel portals over the water . Materials were delivered by a ropeway . There are three levels of galleries , which are no longer military property . Plans are underway to open the complex to visits by the public . Present status . Many of the Saint - Maurice fortifications have been deactivated and are considered potential historic monuments . The Forts de Scex and Cindey are open for tours , and plans are being developed to open the Fort de Vernayaz to the public .