The Fort d'Illange was part of the Moselstellung, a group of eleven fortresses surrounding Thionville and Metz to guard against the possibility of a French attack aimed at regaining Alsace and Lorraine, with construction taking place between 1905 and 1911.

Like the Fort de Koenigsmacker, Illange features an armoured battery, originally armed with four short 100 mm guns in single turrets.

Compared to the French Séré de Rivières system forts of the same era, later German fortifications such as Illange were scattered over a large area and enclosed chiefly by barbed wire.

[2] Illange's fairly compact arrangement includes four dispersed fortified barracks built into a hillside so that their rears are shielded by earth, while the tops and fronts are protected by three of four metres of concrete, and are surmounted by parapets.

The four 100 mm guns in the battery were protected by Schumann turrets and controlled by two armored observation cupolas on top of the north and south barracks.

The whole was surrounded by deep networks of barbed wire, which were swept by fire from small perimeter blockhouses, also linked via the tunnel system.

During the Battle of France the Thionville area was bypassed and encircled by German forces, with the Maginot and earlier fortifications seeing little action.

An American soldier appeared under a white flag to request terms for evacuating the fort, but was told that the Germans would be required to surrender immediately.