Fort de Maulde The Fort de Maulde , also known as Fort de Beurnonville and the Ensemble de Maulde , is located to the south of Maulde , France . It is part of the Fortified Sector of the Escaut , an extension of the Maginot Line . The Séré de Rivières system fort was built 1881 - 1884 . In 1936 - 37 the old fort , commanding high ground behind Maulde , was altered for more modern fortifications . It was evacuated by its garrison in 1940 during the Battle of France as part of the French retreat from the border with Belgium . The site at the top of the Mont de Ligne dominates the plains of the Scarpe and the Escaut , occupying the site of an old military encampment used in 1792 by General Dumouriez against the Austrians . It is within of the Belgian border . The fort is named for Pierre de Ruel , marquis de Beurnonville , a Marshal of France . Description . The original fort is typical of the Séré de Rivières system , with a low wall , surrounded by a ditch , which is in turn defended by two caponier s . The roof of the single - level barracks is concreted and supports an artillery platform , or cavalier . A relatively small fort , it was disarmed in 1912 , then rearmed in 1914 with 90mm guns . In the 1930s the fort was chosen as a site for fortifications associated with the Maginot Line extension around Valenciennes , part of the " New Fronts " program . An observation post and two casemates were built in 1936 - 37 within the walls of the fort . The casemates , facing east and west , were each furnished with two 75mm guns and two automatic rifle ports . To the south , just outside the walls , a north - facing casemate for a 155mm field gun was built , aligned to cover the bridges at Tournai . None of the casemates or the observatory were connected by underground passages in the manner of a fully developed Maginot fortification . A short distance to the north a chain of casemates covered an anti - tank ditch extending about . The position is described as an " ensemble " rather than an " ouvrage " , as a true Maginot fortification would be termed , due to the absence of connecting underground galleries and support facilities . Nevertheless , with four 75mm guns and a 155mm guns , the position was heavily armed . Mauldet was not constructed by CORF ( " Commission d ' Organisation des Régions Fortifiées " ) , the Maginot Line ' s design and construction agency , but by the Army Engineer Service ( " Service Technique du Génie ( STG ) " ) , further removing it from the main Maginot Line . As many as five artillery casemates were planned , but only three were built . In 1939 work was undertaken to link the observation post , 75mm and 155mm casemates by underground passages in a manner similar to Maginot worsk . The excavation was not completed before the outbreak of war in 1940 . Casemates and positions . The casemates are named for their relation to the town of Maulde , rather than to the fort . History . In 1870 , France was partly occupied by the Prussian army . As a result of this defeat , the Séré de Rivières system of fortifications was planned and constructed to defend the nation . Valenciennes , located close by the border between France and Belgium , received additional fortifications . Construction on the Fort de Maulde started in 1881 , completing in 1884 for a garrison of 431 men armed with 27 artillery pieces . In 1890 Valenciennes was declared an open city , and its Vauban - era fortifications in the city center were razed , while the new forts were disarmed . They were hastily rearmed in 1914 , but were captured by the Germans in the opening stages of World War I . Before retreating in 1918 the Germans blew up the fort ' s powder magazine . In the 1930s , France invested in the construction of the Maginot Line , which covered the eastern frontiers of France . The frontier with Belgium was regarded as a lesser priority because France ' s war plan called for the French Army to advance into Belgium and conduct an offensive there . Belatedly , France began construction of a limited series of defenses around Valenciennes in the mid - 1930s . These fortifications were individually assaulted and captured in the opening phases of World War II . Following the fall of Maubeuge in May 1940 , German forces advanced on Maulde , reaching the fort , commanded by Captain Schwengler , by 20 May . Bombardment began that day , but infantry units did not reach the area until the next day , delayed by fire from the 75mm guns of the eastern casemate of Maulde . By the 26th , Maulde ' s peripheral casemates had been captured , and Schwengler was ordered to sabotage and evacuate the fort in the night . The Germans found the fort abandoned on the 27th . After 1940 , the Fort de Maulde was used by the Germans for explosives effects testing , leaving significant damage . After the war it became the property of a tile factory . Present condition . The Fort de Maulde was closed to public access in 2009 , due to the dangers of falling into pits in the darkness of its interior and from falling masonry . Toxic waste from the tileworks was dumped in the fort until the 1980s . Its subsidiary bunkers remain visible in the surrounding fields .