The gros ouvrage[nb 1] was intended to receive a second 75mm gun turret in a second phase of construction, never pursued.

[4] Four-à-Chaux is a position of medium importance on the Line, covering an area of 26 hectares, 4.5 km of subterranean galleries and six combat blocks.

In contrast to most gros ouvrages in northeastern France, Four-à-Chaux's internal railway system was not electrified.

[13] The nearby Casernement de Lembach provided peacetime above-ground barracks and support services to Four-à-Chaux and other positions in the area.

In 1951, Lembach, Four-à-Chaux, Hochwald and Schoenenbourg were designated the Môle de Haguenau, a point of resistance against a potential invasion by forces of the Warsaw Pact.

[19] By the late 1950s interest in fixed fortifications was waning after France developed a nuclear deterrent.

[20] Today, Four-à-Chaux is open to the public under the guidance of the SILE (Syndicat d'Initiative de Lembach et Environs) association.

The guided visit includes Block 2, the barracks, principal gallery, usine and the museum.