Fort de Guentrange The Fort de Guentrange dominates Thionville in the Moselle department of France . It was built by Germany in next to the town of the same name the late 19th century after the annexation of the Moselle following the Franco - Prussian War . The Fort de Guentrange 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 1899 and 1906 . The fortification system incorporated new principles of defensive construction to deal with advances in artillery . Later forts , such as Guentrange , embodied innovative design concepts such as dispersal and concealment . The later forts were designed to support offensive operations , as an anchor for a pivoting move by German forces into France . The Feste Ober - Gentringen , as Fort de Guentrange was called by the Germans , with the Fort de Koenigsmacker and Fort d ' Illange , assured the protection of Thionville against French attack . Positioned to the rear of the principal lines of combat in the First World War , the fort never saw combat in World War I . It is the largest of the three Thionville " festen " . The site overlooks the Moselle valley and its western approaches , as well as the railway lines to the west of Thionville . Description . The Fort de Guentrange is located about to the northwest of Thionville on a hilltop overlooking the town and the northern railway line . It was defended by a garrison of 2000 men . Like the Fort de Plappeville on the heights of Metz , Fort Ober - Gentringen features two dispersed armored batteries , each armed with four short 100mm guns in single turrets . It possesses a separate four - level barracks and about of underground galleries . The austere simplicity of the fort ' s façade is characteristic of the forts of the era . The dispersed , un - walled nature of the later " Moselstellung " was a significant innovation . Compared to the French Séré de Rivières system forts of the same era , later German fortifications such as Guentrange were scattered over a large area and enclosed chiefly by barbed wire . While certain individual elements presented imposing walls to an attacker , these walls were not continuous . The dispersed nature is evidenced by the official French name : the " Groupe Fortifié de Guentrange " ( Fortified Group of Guentrange ) . These arrangements were studied and improved upon by the French in the construction of the Maginot Line . The fort includes three separate fortified barracks along a north - south line , the central barracks being the largest . Each barracks was built into a hillside so that the rear are shielded by earth , while the top and front are protected by three of four meters of concrete , and are surmounted by a parapet . The two batteries are similarly constructed and linked to the barracks by underground tunnels . The four 100mm guns in each battery were protected by Schumann turrets and controlled by an armored observation cupola on top of each battery . 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 . Further counterscarp casemates were built after 1912 when the defensive perimeter was expanded . The interior of the position was equipped with trenches for infantry . The barracks and batteries were further armored with reinforced concrete and armored windows . A variety of blockhouses and infantry shelters were also built in the intervals between forts . The fort featured central heating in the barracks and the armored batteries , as well as a central generating plant for electricity with eight diesel generators . Operational concept . From 1899 , the Germans viewed Metz as a secure position that could provide an anchor for a pivoting movement into France from the Low Countries . This strategy , which would become known as the Schlieffen Plan , required that the " Moselstellung " deter an advance by French forces into Lorraine while the German forces mobilized . History . During World War I , Thionville was located well to the rear of German lines and never came under attack . With the Compiègne armistice of 1918 , Lorraine was returned to France and the fort became French property . The three Thionville forts became known as the Fortified Group of Thionville . The Fort de Guetrange was integrated into the Fortified Sector of Thionville of the Maginot Line in the 1930s , backing up the newer Maginot " ouvrages " that were built about halfway between Thionville and the border with Luxembourg . The short 105mm guns were replaced by 105mm long guns removed from the German fortifications of Metz . The artillery range was thus increased from to . During the Battle of France the Thionville area was bypassed and encircled by German forces , with the Maginot and earlier fortifications seeing little action . After the 25 June 1940 armistice the German occupiers used the fort as a supply depot until Thionville was liberated by the Americans . The Fort de Guentrange was captured without resistance by elements of the U . S . 90th Infantry Division on 12 September 1944 , after the German forces withdrew to Metz . After the war , the French Army used the fort as a munitions depot until 1971 . Manning . Under the Germans , the Feste Ober - Gentringen was occupied in 1909 - 10 by the 8th " Fussenartillerie " ( Foot Artillery ) Regiment . From 1913 , the garrison was provided by the 16th " Fussenartillerie " . The French garrison of the Fort de Guentrange in 1939 - 40 was provided by detachments of the 168th Fortress Infantry Regiment and the 151st Position Artillery Regiment . Present status . The fort is presently the property of the city of Thionville and is maintained by the " Amicale du Groupe Fortifié de Guentrange " , which conducts guided visits .