[2] The Fort du Sapey is the center of an ensemble of fortifications designed to protect Modane, the valley of the Arc and the terminus of the Fréjus Rail Tunnel to Italy, which was completed in 1871.

A special battery was built and excavated into the rock to directly cover the end of the Fréjus tunnel.

[3] The position received a disproportionate amount of resources, considering the limited possibilities for enemy attack through the tunnel or over the Mont Cenis pass.

Manned by 36 soldiers under 4 officers, it mounted ten de Bange 120 mm guns, six in the main fortification and four in an annex.

Entered from the west, the galleries connected to the old abris of the barracks, emerging at combat blocks under the walls for the redoubt on the east side.

[7] The 75mm guns of Sapey Fréjus battery fired on Italian troops in the vicinity La Roue on 20 June 1940.

Fréjus was joined by Battery Maurienne on the 22nd, firing on Italian forces in the vicinity of Bramans.

[14] Sapey had suffered little damage during the war, apart from the destruction of its aerial tram, and by the end of 1944 was partly repaired and placed into service.

Immediately after the war, the Maurienne region was regarded as an area of medium priority for restoration and reuse by the military.

However, by 1960, with France's acquisition of nuclear weapons, the cost and effectiveness of the Maginot system was called into question.