The site was surveyed by the Commission d'Organisation des Régions Fortifiées (CORF), the Maginot Line's design and construction agency, in early 1931.

Fermont was served by a 60 cm-gauge narrow-gauge railway, which enters at the munitions entrance and runs all the way out through the galleries to the combat blocks.

[17] A series of detached casemates and observation points surround Fermont, including the: None of these are connected to the ouvrage or to each other.

The Caserne Lamy provided peacetime above-ground barracks and support services to Fermont and other fortifications in the area.

On the 13th, Fermont provided covering fire for French forces retreating from Longwy, which was between the Maginot Line and the German border and was therefore regarded as indefensible against a determined attack.

In late May and early June the German attack was focused farther to the west, eventually breaking out behind the Line.

On June 17, German artillery of the 183rd Infantry Division opened fire on the rear of Block 4 with 88 mm guns.

By 1951 work was proceeding on renovation of many of the northeastern ouvrages, including Fermont, with the aim of restoring their combat capability to block a potential advance by the Warsaw Pact.

In 1975 the property was transferred from the Ministry of Defense to an association for the restoration and preservation of Fermont, and in 1977 it was opened to the public.