Fort de Fléron The Fort de Fléron is one of twelve forts built as part of the Fortifications of Liège in the late 19th century in Belgium . It was built between 1881 and 1891 according to the plans of General Henri Alexis Brialmont . Contrasting with the French forts built in the same era by Raymond Adolphe Séré de Rivières , the fort was built exclusively of unreinforced concrete , a new material , rather than masonry . The fort was heavily bombarded by German artillery in the Battle of Liège . Fléron was upgraded in the 1930s to become part of the fortified position of Liège in an attempt to forestall or slow an attack from Germany . Located in the center of Fléron , the fort has been buried and is surrounded by apartments . Description . The Fort de Fléron is located about southeast of the center of Liège , in the center of Fléron . The fort formed an isosceles triangle whose base is long and whose sides measured . A deep by ditch encircled the fort . The principal armament was concentrated in the central massif . The ditches were defended in enfilade by 57mm guns in casemates resembling counterscarp batteries , firing at shot traps at the other end of the ditch . One of the larger forts of Liège , it was armed with heavy artillery in rotating turrets , concentrated in a central massif . The compact center was surrounded by four turrets with lighter guns for close defense . With the exception of the Fort de Loncin , the Belgian forts made little provision for the daily needs of their wartime garrisons , locating latrines , showers , kitchens and the morgue in the fort ' s counterscarp , a location that would be untenable in combat . This would have profound effects on the forts ' ability to endure a long assault . The service areas were placed directly opposite the barracks , which opened into the ditch in the rear of the fort ( i . e . , in the face towards Liège ) , with lesser protection than the two " salient " sides . The Brialmont forts placed a weaker side to the rear to allow for recapture by Belgian forces from the rear , and located the barracks and support facilities on this side , using the rear ditch for light and ventilation of living spaces . In combat heavy shellfire made the rear ditch untenable , and German forces were able to get between the forts and attack them from the rear . The Brialmont forts were designed to be protected from shellfire equaling their heaviest guns : 21 cm . The top of the central massif used of unreinforced concrete , while the caserne walls , judged to be less exposed , used . Under fire , the forts were damaged by 21 cm fire and could not withstand heavier artillery . Armament . Fléron ' s armament included 21 cm , 15 cm and 12 cm gun turrets for distant targets and 57mm gun turrets for local defense . It also mounted an observation turret with a searchlight . Rapid - fire 57mm guns were provided in casemates for the defense of the ditches and the postern . The large weapons were all German products , made by Krupp in Essen , but the armor was by Cockerill ( Belgium ) , Ateliers de Creusot ( France ) or Grüson ( Germany ) . The fort was provided with signal lights to permit communication with the neighboring Fort de Loncin and Fort de Liers . The guns were fired using black powder rather than smokeless powder , producing choking gas in the confined firing spaces that spread throughout the fort . The fort was manned by 307 artillerymen and 80 infantry under the command of Commandant - Captain Mozin . First World War . The forts south and east of Liège first came under attack on 4 August 1914 . Heavy German infantry attacks were met with unexpectedly strong resistance , resulting in heavy German casualties . When the Liège ' s fortifications proved unexpectedly stubborn , the Germans brought heavy siege artillery to bombard the forts with shells far larger than they were designed to resist . German forces infiltrating between the forts captured the center of Liège on 6 August and were able to set up siege artillery in the city itself , attacking the forts from the rear . Fléron was hit with heavy artillery starting on the 11th , and by the next day was being hit at a rate of up to 250 shots per hour . A German delegation requesting the fort ' s surrender was turned away at midday , but conditions inside the bombarded fort were poor , and the fort ' s ammunition hoists were inoperable . That night the firing continued with close - range mortar fire . On the 13th a 42 cm gun opened fire . Commandant Mozin surrendered the fort at 0945 hours on the 14th , having lost the means to fight back and unable to remain in the asphyxiating fort . The fort suffered five killed in the battle . Twelve more died as prisoners of war . Fortified Position of Liège . Fléron ' s armament was upgraded in the 1930s to become part of the Fortified Position of Liège II , which was planned to deter a German incursion over the nearby border . The 21 cm turrets were replaced with longer - range 15m turrets , the 15 cm turret was replaced by a turret with machine guns and grenade launchers , and the 12 cm turrets were replaced with turrets containing twin 105mm guns . These new weapons were German in origin . Three 75mm turrets were added as well . This was accompanied by improvements to ventilation , protection , sanitary facilities , communications and electrical power . An air intake tower was added on the other side of the now - vanished Line 38 railroad tracks , which has itself been demolished . New barracks were built at this time for peacetime accommodation . The fort was manned by 250 men , 20 non - commissioned officers and 13 officers . Second World War . From 10 May to 16 May 1940 Fléron was repeatedly attacked by air . The electrical system was destroyed the first day , compelling all firing adjustments and loading to be done by hand . The fort fired on German forces in the area , as well as providing covering fire to neighboring forts . Targets included the Citadel of Liège , the airport , and the Chàteau de Tancrémont . The fort also fired on attacking aircraft . Heavy aerial attacks on 17 May wrecked the communications center and the 15 cm turrets . The 105mm guns ran out of ammunition , and a 75mm gun was inoperable . The fort ' s commandant , Captain Gline , believed that the fort was no longer capable of effective resistance , and with the permission of his superiors released the garrison to join the field army . Four were killed and six wounded during the action . Present . The fort has been buried under a public park and is surrounded by apartments .