The 'Battle of Fort Eben-Emael' was fought between German and Belgian forces for Fort Eben-Emael, a linchpin of the Belgian defence in the 'Battle of Belgium' resulting from the German 'Gelb' invasion of that country (10/11 May 1940).

An assault force of German Fallschirmjäger (paratroopers) was tasked to take Fort Eben-Emael, a Belgian fortress whose strategic position and strong artillery emplacements dominated several important bridges over the Albert Canal. These carried roads which led into the Belgian heartland and were needed by the Germans for the successful implementation of their advance into Belgium. As some of the German airborne forces assaulted the fortress to disabled the artillery inside it and kill or capture the garrison, others simultaneously captured three bridges over the Albert Canal. Having disabled the fortress, the airborne troops were then ordered to protect the bridges against Belgian counterattacks until relieved by ground forces of General Georg von Küchler’s 18^th Army of Generaloberst Fedor von Bock’s Heeresgruppe 'B'.

The battle was an operational-level German victory as the airborne troops landing on top of the fortress in gliders and used explosives and flamethrowers to disable the fortress’s outer defences. The Fallschirmjäger then entered the fortress, killing some defenders and containing the rest in the fort’s lower sections. Simultaneously, the rest of the German assault force had landed near the three bridges over the canal, destroyed several pillboxes and defensive positions, and defeated and captured the Belgian forces guarding the bridges, which were then brought under German control. The airborne troops suffered heavy casualties during the operation, but succeeded in holding the bridges until the arrival of German ground forces, who then aided the airborne troops in assaulting the fortress a second time and forcing the surrender of the remaining members of the garrison. The German ground forces were then able to use two bridges over the canal to bypass Belgian defensive positions and advance into Belgium. The bridge at Kanne was destroyed, forcing German engineers to construct a new bridge.

On 10 May 1940, Germany launched its 'Gelb' invasion of the Low Countries and France. By attacking through the Netherlands, Belgium and Luxembourg, Oberkommando der Wehrmacht planned to outflank the 'Ligne Maginot' and advance through southern Belgium and into northern France, cutting off the British Expeditionary Force and a large (and better) part of the French forces and thereby forcing the French government to surrender. To gain access to northern France, the German forces would have to defeat the armed forces of the Low Countries and either bypass or neutralise several defensive positions, primarily in Belgium and the Netherlands. Some of these defensive positions were only lightly defended and intended more as delaying positions than true defensive lines designed to stop a German attack.

However, some defences were of a more permanent nature, possessed considerable fortifications and were garrisoned by significant numbers of troops. The 'Grebbe-Peel Line' in the Netherlands, which stretched from the southern shore of the IJsselmeer to the Belgian border near Weert, had many fortifications combined with natural obstacles, such as marshland and the Geld valley, which could easily be flooded to impede an attack. The main Belgian defensive line, the 'K-W Line' (also known as the 'Dyle Line' or 'Dijle Line') along the Dyle river, protected the port of Antwerp and the Belgian capital, Brussels. Between the K-W Line and the border was a delaying line along the Albert Canal. This delaying line was protected by forward positions manned by troops, except in a single area where the canal ran close to the Dutch border, which was known as the 'Maastricht appendix' for its proximity to the Dutch city of Maastricht. There the Belgian military could not build forward positions as the area was too close to the border, and instead assigned an infantry division to guard the three bridges over the canal in the area, a brigade being assigned to each bridge. The bridges were defended by blockhouses equipped with machine guns, and artillery support was provided by Fort Eben-Emael, whose artillery pieces covered two of the bridges.

The German high command became aware of the defensive plan, which called for Belgian forces to hold, albeit briefly, the delaying positions along the Albert Canal and then retreat to link with British and French forces on the 'K-W Line'. The Germans developed a strategy that would disrupt this plan, by seizing the three bridges in the 'Maastricht appendix', as well as other bridges in Belgium and the Netherlands. This would allow their own forces to breach the defensive positions and advance into the Netherlands.

The Belgian 7^th Infantry Division was assigned to guard the three bridges over the canal, supplementing the troops who garrisoned Fort Eben-Emael at the time of the battle. The defences for each bridge comprised four large concrete pillboxes on the western side of the canal, three equipped with machine guns and a fourth with an anti-tank gun; the bunker containing the anti-tank gun was sited close to the road leading from the bridge, with one machine gun bunker immediately behind the bridge and the other two flanking the bridge a short distance on each side. A company position existed on the western bank of the canal by each of the bridges, with a small observation post on the eastern side, which could be quickly recalled, and all three bridges could be destroyed with demolition charges set into their structures, triggered by a firing mechanism situated in the anti-tank bunkers.

Fort Eben-Emael, which measured some 200 by 400 yards (180 by 370 m), had been built during the 1930s for completion in 1935, by blasting the required space out of marl. It possessed walls and roofs of reinforced concrete 5 ft (1.5 m) thick, as well as four retractable casemates and 64 strongpoints. The fort was equipped with six 120-mm (4.72-in) pieces of artillery with a range of 17,500 yards (16000 m), two of which could traverse though 360°; 16 75-mm (2.95-in) pieces; 12 60-mm high-velocity anti-tank guns; 25 twin-mounted machine-guns; and a number of anti-aircraft guns. One side of the fort faced the canal, whilst the other three faced land and were defended by minefields, deep ditches, a wall 20 ft (6.1 m) high, and concrete pillboxes armed with machine guns. Some 15 searchlights were installed on top of the fort together with 60-mm anti-tank guns. Many tunnels ran beneath the fort, connecting individual turrets to the command centre and the ammunition magazines. The fort also possessed its own hospital and living quarters, as well as a power station that provided electricity to power the guns, provide internal and external illumination, and power the radio network and garrison’s air-purifying system.

Belgian plans did not call for the garrison of the fort and the attached defending forces to fight a sustained battle against an attacking force: it was assumed that sufficient warning of an attack would be given to allow the detachment on the eastern side of the canal to be withdrawn, the bridges to be destroyed, and the garrison readied to fight a delaying action. The defending force would then retire to the main defensive positions along the Dyle river, where they would link with other Allied forces.

The airborne assault on Fort Eben-Emael, and the three bridges which it shielded, was part of a much larger German airborne operation that involved Generalleutnant Kurt Student’s 7^th Fliegerdivision and Generalleutnant Hans Graf von Sponeck’s 22^nd Luftlandedivision. The former, comprising three parachute regiments and one infantry regiment, was tasked with capturing river and canal bridges that led to the Dutch army’s defensive positions centred on Rotterdam, as well as an airfield at Waalhaven, while the latter, which was composed of two infantry regiments and a reinforced parachute battalion, was tasked with capturing airfields in the vicinity of The Hague at Valkenburg, Ockenburg and Ypenburg. Once these airfields had been secured by the parachute battalion, the rest of the division would land with the aim of occupying the Dutch capital of Amsterdam and capturing the entire Dutch government, the Dutch royal family, and high-ranking members of the Dutch armed forces. The division was also to interdict all roads and railway lines in the area in order to impede the movement of Dutch forces. The intention of the Oberkommando der Wehrmacht was to use the two airborne divisions to create a corridor along which the 18^th Army could advance into the Netherlands without being impeded by destroyed bridges. Student, who proposed the deployment of the two airborne divisions, argued that their presence would hold open the southern approaches to Rotterdam, prevent the movement of Dutch reserves based in north-west Holland and any French Army forces sent to aid the Dutch defenders, and deny the use of airfields to Allied aircraft, all of which would aid a rapid advance by the 18^th Army. A force of 400 Junkers Ju 52/3m three-engined transport aircraft would be used to deploy the parachute elements of the airborne troops, as well as transport the elements of the two airborne divisions not landing by parachute or glider.

The force tasked with assaulting the fort and capturing the three bridges was formed from elements of the 7^th Fliegerdivision and the 22^nd Luftlandedivision as the Fallschirmjäger-Sturmabteilung 'Koch' (Parachute Assault Detachment 'Koch') after the leader of the force, Hauptmann Walter Koch. This force, which had been assembled in November 1939, comprised mostly paratroopers of Oberst Bruno Bräuer’s 1^st Fallschirmjägerregiment and engineers of the 7^th Fliegerdivision, as well as a small group of Luftwaffe pilots. Although the force was composed primarily of paratroopers, it was decided that the first landings should be gliderborne. Adolf Hitler, who had taken a personal interest in the arrangements for the assault force, had ordered that gliders be used after being told by his personal pilot, Hanna Reitsch, that gliders in flight were nearly silent: it was believed that as the Belgian anti-aircraft defence system used sound-location arrays and not radar, it would be possible to tow gliders near to the Dutch border and then release them, achieving a surprise attack as the Belgian defenders would not be able to detect them. Fifty DFS 230 transport gliders were supplied for use by the assault force, which then began a period of intensive training. A detailed study of the fort, the bridges and the area in which they were sited, and a replica of the area was constructed in which the airborne troops trained. Joint exercises between the paratroopers and the glider pilots were carried out early in 1940, and refinements were made to the equipment and tactics to be used: typical of these refinements was he addition of barbed to the gliders' nose-skids to reduce their landing run, and the airborne troops trained with flamethrowers and specialised explosives, the latter of which were so secret that they were only used on fortifications in Germany and not on fortifications in occupied Czechoslovakia similar to Fort Eben-Emael. Secrecy was also maintained in other ways: when the exercises had been completed, the gliders and equipment were broken down and taken away in furniture vans, the force’s sub-units were often renamed and moved from one location to another, unit badges and insignia were removed, and the airborne troops were not permitted to leave their barracks or to take leave.

Koch divided his force into four assault groups. 'Granit', under the command of Oberleutnant Rudolf Witzig, comprised 85 men in 11 gliders, would assault and capture Fort Eben-Emael; 'Stahl', under the command of Oberleutnant Gustav Altmann, comprised 92 men in nine gliders, would capture the Veldwezelt bridge; 'Beton', under the command of Leutnant Gerhard Schacht, comprised 96 men in 11 gliders, would capture the Vroenhoven bridge; and 'Eisen', under the command of Leutnant Martin Schächter, comprised of 90 men in 10 gliders, would capture the Kanne bridge. The critical element for the assault force, and most especially 'Granit', was time. It was believed that the combination of a noiseless approach by the assault force’s gliders and the lack of any declaration of war by the German government, would give the attackers the element of complete operational and tactical surprise. However, German estimates were that this advantage would last, at the most, for 60 minutes, after which the superior numbers of the Belgian forces defending the fort and the bridges, as well as any reinforcements sent to the area, would come to bear against the relatively small number of lightly armed airborne troops. The German plan, therefore, was within those 60 minutes to eliminate as many anti-aircraft positions and individual cupolas and casemates as possible, and at all costs to put out of action the long-range artillery pieces which covered the three bridges. It was expected that the destruction of these guns would be achieved within 10 minutes: within this time the airborne troops would have to break out of their gliders, cover the distance to the guns, fix the explosive charges to the barrels of the guns and detonate them, all the while under Belgian fire.

In its final form, the assault plan called for between nine and 11 gliders to land on the western bank of the Albert Canal by each of the three bridges just before 05.30 on 10 May, the time scheduled for the launch of 'Gelb'. The groups assigned to assault the three bridges would overwhelm the defending Belgian troops, remove any demolition charges and then prepare to defend the bridges against an expected counterattack. Some 40 minutes later, three Ju 52/3m transport aircraft would fly over each position, dropping a reinforcement group of 24 more airborne troops as well as machine guns and significant amounts of ammunition. Simultaneously, the force assigned to assault Fort Eben-Emael was to land on top of the fort in 11 gliders, eliminate any defenders attempting to repel them, cripple what artillery they could with explosive charges, and then prevent the garrison from dislodging them. Having achieved their initial objectives of seizing the bridges and eliminating the fort’s long-range artillery, the airborne troops would then defend their positions until the arrival of German ground forces.

For reasons of security, the Sturmabteilung 'Koch' was dispersed around several locations in the Rhineland until it received orders for the start of the operation against Fort Eben-Emael and the three bridges. Preliminary orders were received on 9 May, ordering the separated detachments to move to a pre-arranged concentration area, and soon after this a second order arrived, informing the assault force that 'Gelb' was to begin at 05.25 on 10 May.

The airborne soldiers filed onto an unlit runway at 03.00. At 04.30, 42 gliders carrying the airborne troops were towed into the air from two airfields at Köln, and the armada of transport/tug aircraft and gliders turning to the south toward their objectives. The aircraft maintained strict radio silence, forcing the pilots to rely on a chain of signal fires that pointed towards Belgium; the radio silence also ensured that senior commanders of the assault force could not be informed that the tow-rope of one of the gliders had snapped, forcing the glider to land inside Germany. The pilot of a second glider released his tow-rope prematurely, and was unable to land near his objective. Both of these gliders were carrying troops of the 'Granit' party, which was thus under-strength for its assault on Fort Eben-Emael. It also left the party under the command of Oberfeldwebel Helmut Wenzel, Witzig’s second-in-command, as Witzig himself was in one of the gliders forced to land. The remaining gliders were released from their tow ropes some 20 miles (32 km) from their objectives at an altitude of 6,890 ft (2100 m), which was deemed high enough for the gliders to land by the three bridges and on top of the fort, and also maintain a steep dive angle to further ensure they landed correctly. After the Ju 52/3m aircraft had released the gliders and started to turn away, Belgian anti-aircraft artillery positions detected them and opened fire, and this alerted the defences in the area to the presence of the gliders.

All nine gliders carrying the troops assigned to 'Stahl' landed next to the bridge at Veldwezelt at 05.20, the barbed-wire wrapped around the landing skids of the gliders successfully bringing them all to a rapid halt. Altmann’s glider had landed some distance from the bridge, and a second had landed directly in front of a Belgian pillbox, which began engaging both groups of airborne troops with small-arms fire. The non-commissioned officer in charge of the troops from the second glider hurled grenades at the pillbox while one of his men laid an explosive charge at the door and detonated it, allowing the bunker to be assaulted and removed as an obstacle. Simultaneously, Altmann gathered his troops and led them along a ditch running parallel with the bridge until two men were able to reach the canal bank and climb onto the girders of the bridge and disconnect the demolition charges placed there by the Belgian garrison. The airborne troops thus prevented the Belgians from destroying the bridge, though they still faced the rest of the Belgian defenders. These last held on until a platoon of German reinforcements arrived and forced them to retire to a nearby village. However, the assaulting force’s small-arms fire could not overcome two field guns located 545 yards (500 m) from the bridge, thus forcing Altmann to call for air support. Several Junkers Ju 87 single-engined dive-bombers responded and knocked out the guns. 'Stahl' was to be relieved by 14.30, but Belgian resistance delayed the relief force’s arrival in strength until 21.30. During the fighting, the attacking force suffered the loss of eight men dead and 30 wounded.

Ten of the 11 gliders transporting 'Beton' landed next to the Vroenhoven bridge at 05.15, the 11^th glider having been hit by anti-aircraft fire en route to the bridge and having to force-land prematurely inside Dutch territory. The gliders were engaged by heavy anti-aircraft fire as they landed, causing one of the gliders to stall in mid-air, the resulting crash severely injuring three of the airborne troops. The rest of the gliders landed without damage. One of the gliders landed near the fortification housing the bridge detonators, and this made it possible for the airborne troops to deliver a rapid assault on the position. The Germans killed the occupants and tore out the wires connecting the explosives to the detonator set, ensuring the bridge could not be destroyed. The remaining Belgian defenders resisted fiercely by mounting several counterattacks as they attempted to recapture the bridge. They were repelled with the aid of several machine guns dropped by parachute to the airborne troops at 06.15. Constant Belgian attacks meant that the 'Beton' party was not withdrawn on relief by an infantry battalion until 21.40 after suffering the loss of seven men killed and 24 wounded.

All but one of the 10 gliders carrying the airborne troops assigned to 'Eisen' were able to land next to their objective, the bridge at Kanne, but as a result of a navigation error by the pilots of the transport aircraft towing the gliders, one of the gliders was dropped in the wrong area. The other nine gliders were towed through heavy anti-aircraft fire and released at 05.35. As the gliders began to descend to their objective, the bridge was destroyed by several demolition explosions initiated by the Belgian garrison. Unlike the garrisons of the other two bridges, the Belgian defenders at Kanne had been forewarned as the German mechanised column heading for the bridge to reinforce 'Eisen' had arrived 20 minutes ahead of schedule, and its appearance ruined any chance of a surprise assault and gave the defenders sufficient time to destroy the bridge.

As the gliders came in to land, one was hit by anti-aircraft fire and crashed into the ground killing most of the occupants. The remaining eight landed successfully, and the airborne troops stormed the Belgian positions and eliminated the defenders. By 05.50 the airborne troops had secured the area as well as the nearby village of Kanne, but then came under a strong counterattack which was repulsed only with the support of Ju 87 dive-bombers. The defenders launched several more counterattacks during what was left of the night, ensuring that the airborne troops could not be relieved until the morning of 11 May. 'Eisen' suffered the heaviest casualties of all three assault groups assigned to capture the bridges, its losses being 22 men killed and 26 wounded. One of the group’s men was taken prisoner by the Belgians, and was later freed by German forces at a British prisoner of war camp at Dunkirk.

The nine remaining gliders transporting the airborne troops assigned to 'Granit' landed successfully on the roof of Fort Eben-Emael, using braking parachutes to slow their descent and bring them to a rapid halt. The airborne troops rapidly disembarked, Wenzel assuming command in the absence of Witzig, and began attaching explosive charges to those emplacements on the top of the fort which housed the artillery pieces that could target the three captured bridges. In the southern part of the fort, Objective No. 18, an artillery observation casemate housing three 75-mm (2.95-in) pieces of artillery was damaged with a light demolition charge and then permanently destroyed with a heavier charge, which collapsed the casemate’s observation dome and part of the roof of the fort itself. Objective No. 12, a traversing turret holding two more pieces of artillery was also destroyed by airborne troops, who then moved to Objective No. 26, a turret holding another three 75-mm (2.95-in) weapons; although explosives were detonated against this and the airborne troops assigned to destroy it moved off, this proved to be premature as one of the guns was rapidly brought to bear against the attackers, who were forced to assault it for a second time to complete its destruction. Another pair of 75-mm (2.95-in) guns in a cupola was disabled, as was a barracks known to house Belgian troops. However, attempts to destroy Objective No. 24 proved to be less successful: the objective, twin turrets with heavy-calibre guns mounted in a rotating cupola, was too large for airborne troops from a single glider to destroy on their own, forcing troops from two gliders to be used. Primitive unlined shaped charges were affixed to the turrets and detonated, but while these shook the turrets they did not destroy them, and other airborne troops were forced to climb the turrets and smash the gun barrels.

In the fort’s northern section, similar actions were taking place as the airborne troops hastened to destroy or otherwise disable the fortifications housing pieces of artillery. Objective No. 13 was a casemate accommodating several machine-guns whose arcs of fire covered the Fort’s western side of the fort: to destroy the casemate, the airborne troops used a flamethrower that forced the Belgian soldiers manning the weapons to retreat, and then detonated shaped charges against the fortification to disable it. Another observation cupola armed with machine guns was Objective No. 19, which was destroyed, but two further objectives, Nos 15 and 16, were found to be dummy installations. Unexpected complications came at Objective No. 23, a retractable cupola housing two 75-mm (2.95-in) pieces of artillery. It had been assumed that the weapons in this fortification could not stop the airborne assault, but this assumption was found to be false when the weapons opened fire, forcing the airborne troops in the area to take cover. The rapid fire of the weapons led to air support being summoned, and a Ju 87 squadron attacked the cupola: although the bombs did not destroy the cupola, the explosions did force the Belgians to retract it throughout the rest of the fighting. All exterior entrances and exits located by the airborne troops were destroyed with explosives to seal the garrison inside the fort, giving the garrison few opportunities to attempt a counterattack. The airborne troops had achieved their initial objective of destroying or disabling the artillery pieces that the fort could have used to bombard the captured bridges, but they still faced some small cupolas and emplacements that had to be disabled. These included anti-aircraft weapons and machine-guns.

As these secondary objectives were attacked, a single glider landed on top of the fort, and from this emerged Witzig. After his glider had unintentionally landed in German territory, he had radioed for another tug, which had landed in the field with a replacement glider. Once the airborne troops had broken down fences and hedges obstructing the take-off path, they boarded the new glider and were towed through anti-aircraft fire to the fort.

Having achieved their primary objectives of disabling the artillery pieces possessed by the fort, the airborne troops then held it against Belgian counterattacks, which began almost immediately. These counterattacks were made by Belgian infantry without artillery support, and were unco-ordinated, which allowed the airborne troops to repel them with machine gun fire. Artillery fire from several smaller forts in the area and from Belgian field artillery units also targeted the airborne troops, but this effort too lacked co-ordination, achieved nothing and in fact several times aided the airborne troops in repelling Belgian infantry counterattacks. Patrols were also used to ensure that the garrison remained in the fort’s interior and did not attempt to emerge and mount an attempt to retake the fort. However, any attempt by the garrison to launch a counterattack would have been stymied by the fact that the only possible route was up a single, spiral staircase, and any embrasures looking out onto the fort had either been captured or disabled. The German plan for the assault had called for 'Granit' to be relieved Oberstleutnant Hans Mikosch’s 51^st Pionierbataillon within a few hours of the fort’s seizure, but 'Granit' was not actually relieved until 7.00 on 11 May. Heavy Belgian resistance, as well as several demolished bridges over the Meuse river, had forced the battalion to erect new bridges, delaying it significantly. Once the airborne troops had been relieved, the battalion, in conjunction with an infantry regiment that arrived shortly after the engineers, mounted an attack on the main entrance to the fort. Faced with this attack, the garrison surrendered at 12.30 after losing 60 men killed and 40 wounded. The Germans captured more than 1,000 Belgian soldiers. The 'Granit' force had suffered six men killed and 19 wounded.

The German airborne assault on the three bridges and Fort Eben-Emael had been an overall success for the Fallschirmjäger of the Fallschirmjäger-Sturmabteilung 'Koch'. Fort Eben-Emael’s artillery had been disabled, and two of the three bridges designated to be captured by the sub-units of the Fallschirmjäger-Sturmabteilung 'Koch' had been captured before they could be destroyed. The seizure of the bridges and the neutralisation of Fort Eben-Emael’s artillery allowed the 18^th Army's infantry and armour to bypass other Belgian defences and drive into the heart of Belgium.

After the end of 'Gelb', the Fallschirmjäger-Sturmabteilung 'Koch' was elevated to become 1^st Bataillon of the newly formed 1^st Luftlande-Sturmregiment of four Fallschirmjäger battalions trained as a gliderborne assault force. Koch was promoted to the rank of major for his part in the operation and assumed command of the battalion.