Fortified Position of Liège The fortified position of Liège was established following World War I by Belgium to fortify the traditional invasion corridor from Germany through Belgium to France . The Belgian experience of World War I , in which the Belgian Army held the invading force for a week at Liège , impeding the German timetable for the conquest of France , caused Belgium to consider a refined defence strategy . Belgium upgraded the existing fortifications of Liège and extended them onto the Herve plateau closer to Germany , using the most advanced fortifications available to Belgian military technology . However , in 1936 , Belgium ' s neutrality was proclaimed by King Leopold III of Belgium in a vain attempt to forestall another conflict , preventing France from being able to make active use of the Belgian defences and territory in the forward defence of France . At the outbreak of World War II , Belgium ' s defences had to resist alone until France could advance into Belgium after neutrality failed . This time the fortifications could not hold the Germans . The " position fortifiée de Liège " was divided into the modern defensive line , anchored on the Albert Canal by Fort Eben - Emael and extending to the south through a planned five additional forts , designated PFL I , and the ring of forts around Liège itself . Liège commanded crucial road and rail crossings of the Meuse , and remained as strategically important in the 1930s as in 1914 . The modernized Liège forts were designated PFL II . The Liège fortress ring . The first modern forts at Liège were built between 1888 and 1891 at the initiative of Belgian General Henri Alexis Brialmont . The forts made a belt around Liège at a distance of about from the city centre . 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 standardised details . Forts were typically triangular to minimise 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 armoured 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 57mm guns provided close defense . The forts were each equipped with a steam - powered electrical generating plant powering lights , pumps and searchlights . 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 . Twelve First World War forts . Starting from the north , right bank of the Meuse : Two older strongpoints were de - rated in 1891 and played no significant role in either war : Two additional Brialmont forts were planned , one at Visé , where the Meuse could be forded near Lixhe , on the Dutch frontier . The other fort was planned to go between Namur and Liėge at Huy , to block movement along the Meuse between the cities . Neither was built . The Liège forts in 1914 . War did come in 1914 , and Liège became the early focus of German attack on the way to France . The forts were known to have shortcomings in their ability to resist heavy artillery , but had never been modernised . During the Battle of Liège the forts were pounded by heavy German artillery of 21 cm , 28 cm and greater . The forts had never been designed to resist such heavy artillery . The bombardment exposed the forts ' shortcomings in living arrangements , sanitation , ventilation , construction and protection , culminating with the explosion of the Fort de Loncin under bombardment . Even before this the forts had begun to surrender one by one as they became uninhabitable and unable to respond to attack . German forces defeated the troops assigned to defend the intervals between forts , penetrating to Liège and taking it before the first fort had surrendered . The forts ' mission was to delay the progress of an enemy for the time required for the Belgian Army to mobilise . Left to themselves , the forts were planned to resist a siege for about a month , based on estimates made in 1888 . In 1914 the forts were completely outclassed by the much more powerful German artillery , which included the enormous Big Bertha 42 cm howitzer . It was therefore a surprise that the forts resisted as long and as successfully as they did . However , the forts ' poor ability to deal with powder gases , pulverized dust and the stench from inadequate sanitary facilities became a determining factor in the endurance of the forts ' garrisons . None of the forts , apart from the Fort de Loncin , possessed forced ventilation . 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 bombardments 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 . Battle of Liège . In the Battle of Liège the Liège fortifications fulfilled their role , stopping the German army long enough to allow the Belgian and French armies to mobilize . The battle revealed shortcomings in the performance of the forts and in the Belgian strategy . The forts themselves suffered from inherent weakness of construction through poor understanding of concrete technology , as well as overall inadequate protection for the garrison and ammunition stores from heavy - caliber artillery bombardment . Unbreathable air from bombardment , the fort ' s own gun gases and from human waste compelled the surrender of most of the positions . However , the days - long delay caused by the fortress ring allowed the Belgian , and more importantly , the French armies to complete their mobilizations . Had the Germans captured Liège as they had hoped , by a bold stroke , the German army could have been in Paris before France could organize its defence at the First Battle of the Marne . " Position Fortifiée de Liège " . The Fortified Position of Liège was conceived by a commission charged with recommending options for the rebuilding of Belgium ' s defences . The 1927 report recommended the construction of a line of new fortifications to the east of the Meuse . Work was seriously delayed by budget crises , forcing work on all fortifications but Eben - Emael to be delayed . Work finally began on the forts at Battice , Aubin - Neufchâteau and Tancrémont in 1933 . Two other planned positions were never pursued , with Aubin - Neufchâteau taking over the role of forts planned at Mauhin and Les Waides . There were five layers to the system : PFL II . The Belgians initially rebuilt eight forts of the ring to the south and east of Liège , with later work on the west side of the fortress ring . It was not possible to repair the Fort de Loncin , which had been completely destroyed by its own magazines in 1914 . The improvements addressed the shortcomings revealed by the Battle of Liège , allowing the fortress ring to be a backstop to the primary line of fortifications farther east . The Liège ring was designated PFL II , although the forts on the west side of the river were part of PFL IV . Improvements included replacing 21 cm howitzers with longer - range 15 cm guns , 150mm howitzers with 120mm 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 . PFL I . Four new forts were built about to the east of Liège , of a planned six . In contrast to the ring of forts protecting Liège , the new fortification line was similar in concept to the French Maginot Line : a series of positions in a line along the frontier , intended to prevent an enemy advance into Belgian territory , rather than to defend a specific strong point . This new line was designated PFL I , the primary defence line against an advance from Germany , as well as a German advance through Dutch territory at Maastricht . Fort Eben - Emael was positioned to defend the water obstacle of the Albert Canal and to anchor the northern end of the line , with a field of fire all the way north to Maastricht . The Fort de Battice occupied the second strategic point on the main road and rail lines from Aachen . The forts de Tancrémont and Aubin - Neufchâteau filled in the intervals . The cancelled Fort de Sougné - Remouchamps was to be similar to the smaller forts , while plans for two small forts at Comblain - du - Pont and Les Waides were abandoned early in the planning process . The big forts had as many as 2000 men , the smaller 600 . While the organization of the overall defensive line mimicked the Maginot Line , the design of the individual forts was conservative . In contrast to the French fortifications , distributed along a single main gallery in the " fort palmé " concept , the Belgian forts remained a set of powerfully - armed , tightly grouped combat blocks surrounded by a defended ditch . Eben - Emael and Battice featured 120mm gun turrets with a range of , and all four forts were equipped with 75mm gun turrets ( ) and French 81mm mortars in pit emplacements . Eben - Emael , with its site along the artificial cliff of the Albert Canal cutting , was the only fort to be equipped with artillery casemates . The sheer face also provided a naturally - defended location for the fort ' s air intakes . The new forts featured extreme levels of concrete and armour protection , with between and of concrete cover and up to of armour on turrets . Learning from World War I , the intervals between forts were liberally supplied with observation positions and infantry shelters . Forts built before the Second World War . Starting from the north Personnel . In 1940 the Fortified Position of Liège was commanded by Colonel Modart , assisted by Colonel Rosa . They commanded five regiments : Second World War battles . The Belgian command was counting on Eben - Emael to be the key defense of the northern frontier at Liège . It naturally attracted the first German attacks . Its enormous dimensions dictated an unconventional attack strategy , using airborne troops . The fort was attacked on 10 May 1940 and rendered ineffective in a few hours by a team of 75 men armed with new shaped - charge explosives . Ineffective Belgian defense of the fort ' s surface allowed the German assault team to use their explosive charges to destroy or render the fort ' s gun turrets and machine gun cloches uninhabitable . With Eben - Emael out of action , the Germans could attack the other new forts with more conventional means , continuing attacks from 10 May . The forts of both PFL I and II attempted to support each other with covering fire , but to little effect . The PFL I forts quickly fell , with Battice and Aubin - Neufchâteau surrendering on 22 May . Tancrémont was bypassed . The PFL II forts were assaulted starting 12 May after Belgian field forces retreated from Liège . Isolated , the forts fought on . Fort de Flémalle came under air attack on 15 May , surrendering the next day . On 18 May Fort de Barchon was assaulted by the same infantry battalion that had attacked Ebel - Emael , supported by a 420mm howitzer . The fort surrendered the same day , as did Fléron and Pontisse . Evengnée surrendered on 20 May . The other forts to the south were bypassed and surrendered on 28 May , part of the general Belgian surrender . Tancrémont held out until the next day , the last fort to surrender . During the Second World War Eben - Emael was abandoned , apart from use for propaganda films and weapons effects experiments , including armor - piercing shells . Battice and Aubin - Neufchâteau were also used for these experiments . Present day . Of the dozen Brialmont forts , seven are open to the public and may be visited - Loncin , Lantin , Flémalle , Hollogne , Pontisse , Barchon and Embourg . Chaudfontaine may also be visited under certain circumstances , but has not been rehabilitated . The Fort de Loncin has since the explosion of 15 August 1914 , been a military cemetery and memorial . The Fort de Lantin has been extensively restored , and since it was not re - armed between the wars , it presents the appearance of an 1888 fort . Other forts have been partially buried ( Fléron , Boncelles ) and are not visitable , apart from the air intake tower of Boncelles . Others are supply depots for the Belgian army . The four inter - war forts are in varying states of preservation , though all may be visited . Tancrémont is notably intact , with all equipment present . Eben - Emael and the others remain military property , but Eben - Emael is administered by the Association Fort Eben - Emael as a museum .