Battle of Liège The Battle of Liège was the opening engagement of the German invasion of Belgium , and the first battle of World War I . The attack on the city began on 5 August 1914 and lasted until the 16th when the last Belgian fort finally surrendered . The invasion of Belgium was the event that triggered the United Kingdom ' s entry into the war ; the unexpected vigor of the city ' s defence allowed more time for the western Allies to organize and prepare their defence of France . The Schlieffen plan . As Imperial Germany feared a long two - front war against France and the Russian Empire , the Schlieffen plan was conceived which suggested a quick strike to beat France first ( as was done successfully in the Franco - Prussian War of 1870 ) , and then an eastward turn toward Russia ( which was seen as being slower to mobilize ) . In order to do this neutral Belgium had to be crossed within a few days . The highly fortified city of Liège was in the path of the German forces as they advanced through Belgium . Outbreak of war . The summer of 1914 saw tremendous diplomatic and military activity as a result of the assassination of Archduke Franz Ferdinand , the crown prince of Austria . As the summer wore on , war became inevitable . Germany , honoring her alliance with Austria , declared war on Russia on 1 August , she then sent an ultimatum to France ( Russia ’ s ally via the Triple Entente ) on 2 August . Another ultimatum also went to King Albert I of Belgium . Germany ’ s Schlieffen Plan ( developed over the previous two decades ) , called for a vast sweep of manpower around the concentration of French armies along the Alsace frontier . That flanking maneuver , designed to bypass both the French forces and the rugged terrain of the Ardennes , necessitated the German violation of Belgian neutrality . Belgium could have chosen to offer no resistance and allow German troops through her land on their way to France . Indeed , much of the German planning depended on them doing so ; anything else would be nothing more than " the rage of dreaming sheep " , according to one Prussian officer . Unfortunately for German plans , Belgium proved all too willing to defend her sovereignty . Unfortunately for the Belgians , their resources did not match their " élan " . Belgium ’ s fixed defences and planning were dependent on resisting any potential enemy : Germany , France or Britain . At the beginning of August 1914 her armies were on the perimeters of the country , as they had been for years . When Albert received the ultimatum from Berlin , his chief of staff , General Selliers de Moranville , began implementing the standing contingency plan : to concentrate the army in the center of the country while allowing the fortifications at Liège and Namur to slow - down , if not stop , the German advance . Liège straddled the primary road through Belgium toward France . To the south the ground was rugged , to the north it was open but less than a dozen miles from the Netherlands , which Germany did not want to enter . Both Liège and Namur possessed outstanding fortifications , but also had serious shortcomings . Liège was surrounded by a dozen forts , designed and built by Henri Alexis Brialmont , the leading fortress engineer of the nineteenth century . Rejecting the star fort system of the French master Vauban , Brialmont designed forts to resist newer rifled cannon . They existed mainly underground , exposing only mounds of concrete , masonry and soil . Each fort possessed a series of retractable cupolas that held guns ranging in size up to 6 inches . While state - of - the - art upon their completion in 1892 , they had not been well maintained . Brialmont also called for smaller fortifications and trench lines to be built linking and protecting the main forts , but the Belgian government had not done that either . Their garrisons were not at full strength and many men were drawn from the local guard units and had received minimal training . On 2 August King Albert responded to Germany ’ s ultimatum by ordering that work begin on support works , as well as that the army be mobilized and brought up to proper strength . The commander of the Liège fortresses , Lieutenant General Gérard Leman , was ordered to " hold to the end with your division the position which you have been entrusted to defend . " There was little opportunity for the Belgian forces to finish all their preparations , German forces entered the country early on 4 August . The German force detailed to occupy Liège was a provisional unit called the Army of the Meuse , consisting of eight brigades commanded by General Otto von Emmich . Emmich commanded primarily infantry and cavalry and was detailed to capture the bridges across the Meuse at Liège and seize the town if it offered any resistance . When his troops reached the river and found many of the bridges destroyed , they began work on pontoon replacements . When these came under fire , the Germans realized that they would indeed be forced to fight for Liège . Fortifications . Liège lies at the confluence of the Meuse and Ourthe rivers , between the Ardennes Forest to the south and Maastricht of the Netherlands and the flat plain of Flanders to the north and west . The Meuse flows through a deep ravine at Liège , posing a significant barrier . The city lies on the main rail line leading from Germany to Brussels , and eventually to Paris – the same railway that von Schlieffen and von Moltke had planned to use as transport into France . Massive industrial facilities , factories and other installations would assist in the defence of the city . The main defences however , were a ring of twelve forts which had been completed in an 6 – 10 km radius around the city in 1891 . The forts overlapped each other ' s protective zones of fire and were designed so that if any one fort were attacked , its two neighbors could provide artillery support . They were approximately 4 km apart . The forts were triangular or quadrangular in shape , with a surrounding ditch and barbed - wire entanglements . They were made entirely of concrete and armed with 210 mm howitzers , 150 mm and 120 mm cannons and 57 mm rapid - fire guns for approach defence . The fort was defended from attack by infantry with rifles and machine guns . The main guns were mounted in steel turrets that revolved 360 degrees . Only the 57 mm turret could be elevated . In total the forts had 78 pieces of artillery . They contained magazines for the storage of ammunition , crew quarters for up to 500 men and electric motors for lighting . The forts were not linked together and could only communicate with each other by above - ground telephone or telegraph . The forts had several other weaknesses . The terrain was difficult to completely cover since many ravines ran between the forts . Interval defences were constructed just before the battle and were insufficient to stop the Germans from infiltrating the city . The forts were also weak in the rear , the direction from which the German bombardments would eventually come . Ventilation and sanitary conditions were very bad , resulting in a lack of air and terrible odors . Finally , the concrete was not the best quality and the forts were built to withstand assault from 210 mm guns , the largest mobile guns available in 1890 . Leman had been personally selected to command the 3rd Division and the Liège fortifications ; he was under orders from King Albert to hold the fortress system to the end . Leman had a force of about 30 , 000 soldiers to defend the intervals and about 6 , 000 fortress troops , including members of the Garde Civique . Order of battle . Belgian order of battle . The 3rd Belgian Division defended Liège ; it was commanded by Lieutenant General Gérard Leman . Within the division , there were four brigade s and various other formations : Overall , there were about 36 , 000 troops and 252 artillery pieces to face the German invasion . German order of battle . The German attack force ( named The Army of the Meuse ) consisted of : Overall , the force consisted of about 59 , 800 troops and 100 artillery pieces . These were placed under the command of General Otto von Emmich , accompanied by Erich Ludendorff as an observer for the General Staff . The battle . War was declared on Belgium on the morning of 3 August , the lead elements of ' Army of the Meuse ' crossed the border at 0800 on the 4th . The cavalry advanced to the Meuse river , but found that the bridges had been destroyed . By the late afternoon of 4 August , the German cavalry had crossed the Meuse to the north at Visé and encountered troops of the 12th Brigade , who had conducted a valiant retreat to the fortress line . German forces were held in check in the north for the night . The Belgian 3rd Division guarded the town from behind hastily constructed earthworks , on the same day they successfully repulsed attacks by German infantry passing between the forts . An attack against Fort Barchon was beaten back with heavy losses due to machine - gun and artillery fire . After this failed attack , the Germans carried out one of the first air raid s in history by using a Zeppelin to drop bombs on Liège . Meanwhile cavalry moved south from Visé to encircle the town . With the town likely to be invested soon , Leman ordered the 3rd Division to withdraw and rejoin the mobilizing Belgian army to the west . On 6 August , General Ludendorff rode forward to find that the commander of the 14th Brigade had been killed . He took personal command , ordered up a field howitzer to provide fire support and fought through the village of Queue - du - Bois to a high point from where he could look down into Liège . Ludendorff sent a party forward under a flag of truce to demand Leman ' s surrender ( which was refused ) . A raiding force that followed was shot down at the door of Leman ' s HQ . This sally prompted Leman to leave the city and take refuge in Fort Loncin on the western side of the city . The outer ring of forts continued to hold out , blocking the German advance due to their interdiction of the rail lines . The forts endured steady bombardment and attack by the German forces , but most of the forts continued to hold out . Only Fléron was put out of action , its cupola - hoisting mechanism being destroyed by shell fire . The only fort to be captured by infantry assault would be Fort Barchon , taken on 10 August . To reduce these fortifications , the Germans would have to employ their massive siege artillery . These would include the Krupp " Big Bertha " 420 mm howitzers and some loaned Austro - Hungarian 305 mm mortars built by Škoda . At the time of construction of the forts it was assumed that the largest guns that could be moved overland were 210 mm howitzers , so they were not designed to withstand the enormous shells from the larger guns . The shells from these guns landed on the forts from directly above , penetrating the concrete sides and then detonating inside by means of a delayed fuse . One by one the forts were pounded into submission , with the last , Fort Boncelles , capitulating on 16 August . On 15 August Leman was injured at Fort Loncin , he was carried out unconscious to become a prisoner of the Germans . By the morning of 17 August , the German First , Second and Third Armies , in accordance with the Schlieffen Plan , were gearing up to move on with a sweeping push through the rest of Belgium , forcing the remains of the Belgian Army towards Antwerp and capturing Brussels without a fight on 20 August . Aftermath . It is not clear what effect the ten - day resistance in and around Liege by Leman and his troops had on the timetable of the German Schlieffen Plan . What is evident is that the battle was regarded as a moral victory by the allies . No one had expected the Belgians to fight at all , certainly not to fight so effectively . Could the major powers of Europe not fight to the end if tiny Belgium had ? " The triumph was moral — an advertisement to the world that the ancient faiths of country and duty could still nerve the arm for battle , and that the German idol , for all its splendour , had feet of clay " . This regard is further demonstrated by France ' s awarding the city of Liege with the Légion d ' honneur in 1914 . Another effect was a reduction in faith with regard to fortifications , felt by all sides and leading to the weakening of the forts around the city of Verdun , France . This weakening would have an impact on the battle fought there in 1916 .