Fortified Position of Namur The fortified position of Namur ( " position fortifiée de Namur " ( PFN ) ) was established by Belgium following World War I to fortify the traditional invasion corridor between Germany and France through Belgium . The position incorporated the fortress ring of Namur , originally designed by Belgian General Henri Alexis Brialmont to deter an invasion of Belgium by France . The old fortifications consisted of nine forts built between 1888 and 1892 on either side of the Meuse , surrounding Namur . In the years immediately prior to World War II the forts were modernized to address shortcomings exposed during the 1914 Battle of Liège and the short siege of Namur . While the Namur defenses continued to nominally deter France from violating Belgium ' s neutrality , the seven upgraded forts were intended as a backstop to the fortified position of Liège , which was designed to prevent a second German incursion into Belgium on the way to France . The neutrality policy and fortification programs failed , and the Namur forts saw brief combat during the Battle of Belgium in 1940 . The Namur fortress ring . The first modern forts at Namur were built between 1888 and 1892 at the initiative of Belgian General Henri Alexis Brialmont . The forts made a belt around Namur at a distance of about from the city center . Following the Franco - Prussian War , both Germany and France had extensively fortified their new frontiers in Alsace and Lorraine . Belgium ' s comparatively undefended Meuse valley provided an attractive alternative route for forces seeking invade either France or Germany . The plains of Flanders could provide transportation , food and fuel for an invading force . Brialmont recognized that France and Germany would once again go to war . Fortifications at Liège and Namur might dissuade France and Germany from fighting their next war in Belgium . The Liège fortifications were intended to deter Germany , while the Namur forts were to dissuade the French . The forts were built using a small set of basic plans , with standardized details . Forts were typically triangular to minimize the number of defensive batteries in the forts ' defensive ditches , presenting their apex to the enemy . Construction began on 28 July 1888 . The work was carried out by a French consortium , Hallier , Letellier Frères and Jules Barratoux . All of the new forts were built of concrete , a new material for the time , and were equipped with the most modern arms available in 1888 . The concrete was placed in mass , without reinforcement . Lack of useful nighttime illumination in the 1880s meant that concrete could only be placed in daylight , causing weak joints between partially cured daily pours . The forts ' heavy 12 cm , 15 cm and 21 cm guns were made by the German Krupp firm , and were housed in armored steel turrets made by various French , Belgian and German firms . The forts of Liège and Namur mounted a total of 171 heavy guns , at an overall cost of 29 million francs . Lighter 57 mm guns provided close defense . The forts were each equipped with a steam - powered electrical generating plant powering lights , pumps and searchlights . Forts . The Namur forts are arranged as follows : Other fortifications of Namur , obsolete in Brialmont ' s time , included the Citadel of Namur . While it served no military purpose , it was used in the 1930s as the PFN command post , housed in an old tunnel network under the citadel . All of the forts were built entirely in concrete , a new material for the time , rather than the more traditional masonry . The concrete was poured in mass , without reinforcement . The forts were equipped with guns of equal or greater power than those commonly used as siege artillery in 1888 , 22 cm for the French and 21 cm for the Germans . The forts ' military purpose was to delay an enemy advance , allowing Belgian forces to mobilize . Of triangular or quadrilateral form depending on the terrain , the Namur forts are identical in design to the forts of the fortified position of Liège , with a central massif with concrete cover of to thickness , surrounded by a defended ditch wide . The single entries are placed in the rear or the fort , facing Namur , with a long access ramp . The entry is defended by several elements : Each fort possessed three types of armament : In 1914 each fort also possessed a detachment of infantry which in theory could make sorties onto the surrounding cleared areas to harass a besieging enemy . In practice , it was impossible to make such sorties under German artillery fire . Happily for the defenders , the dispersion of German artillery fire was considerable . At least 60 % of German shells , and more for large pieces , failed to find their targets . The fortress guns were less powerful than the German guns , but were more accurate and could take advantage of observation and fire support provided by neighboring forts . 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 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 weapons and could not withstand heavier artillery . The Namur forts in 1914 . Namur was invested by the German Second ( von Bülow ) and Third ( von Hausen ) Armies with approximately 107 , 000 men on 16 August 1914 . Namur was garrisoned by about 37 , 000 in the forts and under the Belgian 4th Division ( Michel ) . The Belgian goal was to hold at Namur until the French Fifth Army could arrive . After attacking the Fort de Marchovelette on 20 August , the Second Army started general fire the next day . At the same time , hoping to prevent the French Fifth Army from reinforcing , the Second Army attacked in the direction of Charleroi . This action was successful , with only one French regiment making it to Namur . During the siege of Namur the Germans employed the lessons learned from their assault on the similar fortress ring of Liège . Unlike at Liège , where a quick German assault gave way to siege tactics , at Namur the Germans immediately deployed siege artillery on 21 August 1914 . The guns included Austrian 304 mm mortars and 420 mm Big Bertha howitzers , firing from beyond the range of the forts ' guns . The contest was unequal , and the forts suffered the same problems that plagued the Liège forts . Namur was evacuated by field forces on 23 August , the forts surrendering immediately afterwards . 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 had profound effects on the forts ' ability to endure a long assault . These 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 . This arrangement was calculated to place a weaker side to the rear to allow for recapture by Belgian forces from the rear , and in an age where mechanical ventilation was in its infancy , allowed natural ventilation of living quarters and support areas . However , the concept proved disastrous in practice . Heavy shellfire made the rear ditch untenable , and German forces were able to get between the forts and attack them from the rear . The massive German bombardment drove men into the central massif , where there were insufficient sanitary facilities for 500 men , rendering the air unbreathable , while the German artillery destroyed the forts from above and from the rear . The Namur forts presented less of a check to the German advance than the Liège forts , as the Germans quickly assimilated the lessons of Liège and applied them to the nearly identical fortifications of Namur , but taken together the Belgian fortifications held the German advance for several days longer than the Germans had anticipated , allowing Belgium and France to mobilize , and preventing the Germans from falling on an unprepared Paris . " Position Fortifiée de Namur " . The Fortified Position of Namur was conceived by a commission charged with recommending options for the rebuilding of Belgium ' s defenses following World War I . The 1927 report recommended the construction of a line of new fortifications to the east of the Meuse . These new forts included Fort Eben - Emael on the Belgian - Dutch - German border , designated " Position Fortifiée de Liège I " ( PFL I ) , backed up by the renovated Liège fortress ring , PFL II . The " Position Fortifiée de Namur " ( PFN ) was a further fallback , while securing the road and rail crossings of the Meuse at Namur . The Belgians rebuilt seven of the Namur forts from 1929 . The improvements addressed the shortcomings revealed by the battles of Liège and Namur . Improvements included replacing 21 cm howitzers with longer - range 15 cm guns , 15 cm howitzers with 120 mm guns , and adding machine guns . Generating plants , ventilation , sanitation and troop accommodations were improved , as well as communications . The work incorporated alterations that had already been made by the Germans during their occupation of the forts in World War I . Most notably , the upgraded forts received defended air intake towers , intended to look like water towers , that could function as observation posts and emergency exits . The remaining two forts were used for ammunition storage . 1940 . During the Battle of Belgium in May 1940 , the Belgian VII Corps , consisting of the 8th Infantry Division and the Chasseurs Ardennais established a strong position in the Namur defenses , anchoring the southern end of the Dyle line . However , Namur was outflanked to the south by German forces that had broken the French line at Sedan , and VII Corps pulled back without a fight to avoid entrapment . The forts took initial German fire on 15 May . Marchovelette surrendered on 18 May , Suarlée on 19 May , Malonne and Saint - Héribert on 21 May , and Andoy and Maizeret on the 23rd . Maizeret was targeted by German 88 mm anti - aircraft guns , which would provide to be accurate and highly effective against fixed armored targets . Present day . In contrast to the Liège fortifications , where seven of the Brialmont forts and all of the PFL I forts may be visited , none of the Namur forts are visitable by the public . All are on private or military property . St . Héribert has been buried and Malonne is closed as a refuge for bats .