Belgian fortifications in WWII

Defensionem Countries Belgium Belgian fortifications in WWII

Belgian fortifications in WWII. As early as in the 1920’s, it was already clear that yet another war was coming to Europe. Toward the end of that decade, Belgium was already refurbishing 8 of its old forts around Liege, digging new structures below them to store ammunition and shelter the men deeper. Both existing galleries and new ones received injections of reinforced concrete.

Throughout the 1930’s, Belgium built several fortified sectors and positions. In Namur, the PFN (Namur Fortified Position) was made up of 7 Brialmont forts which were modernised along the same lines as the ones situated in Liege. The forts anchored a defensive perimeter around the city and were supplemented by 156 bunkers.

Belgian fortifications in WWII
PFN (All Rights reserved Bernard Vanden Bloock)

In Antwerp, the old outer ring of forts was repaired and turned into Armoured Infantry Positions, their older gun turrets replaced by machine gun bunkers. The interval redoubts were also repaired and turned into Armoured Infantry Positions. In total, the Antwerp Fortified Position (PFA) was defended by 23 forts and redoubts and 560 bunkers.

Belgian fortifications in WWII
PFA (All rights reserved Bernard Vanden Bloock)

Linking Antwerp to Namur was the KW line (Dyle line). It ran 60 kilometres between the PFA and the PFN. Its fortifications were composed of 235 bunkers. Behind this line was the small independent Mechelen Bridgehead with its 21 bunkers. There was, however, an unfortified 28km gap between the KW line and the Namur Fortified Position called the Gembloux Gap. The Gap was simply protected by obstructions.

Belgian Fortifications in WWII
KW Line (All Rights Reserved Bernard Vanden Bloock)

The Ghent Bridgehead around the city of the same name was made up of 228 bunkers.

Finally, there was the Liege Fortified Position (PFL). Due to its proximity with Germany, the PFL was the strongest fortified position in Belgium and was composed of 5 layered fortified lines of defence between Liege and the German border. Four new modern forts (Eben-Emael, Aubin-Neufchateau, Battice and Tancremont) were built in Liege. Situated ahead of the older modernised forts, they were designed along the same Brialmont principles that had worked well in 1914, but sought to integrate solutions to the problems encountered by the design in WWI.

Belgian Fortifications in WWII
PFL Position Blue: Forward Positions Yellow: PFL1 Pink: PFL2 Orange: PFL3 Green: PFL4

It is important to understand that forts were not built to operate individually: They were all part of an integrated fortified position designed to defend in-depth. Those forts spawned a whole ecosystem to support them and work alongside them, such as a dedicated underground phone network with telephone exchanges, dozens of Armoured Observation Bunkers and hundreds of various types of other bunkers. There were also lines of anti-tank obstacles and trenches. Finally, Belgian army troops were meant to position themselves along those lines of defences and between the forts’ intervals.

The first line of the PFL was the “forward line”. It was composed of 66 bunkers along the German border and centred around the towns of Beusdael, Hombourg, Henri-Chapelle, Grunhault, Dolhain, Jalhay, Hockay, Malmedy and Stavelot. This line was not meant to be held hard but instead used as a delaying screen to hamper German advances and cover the retreat of border guard units.

The first solid main line of defence was the PFL1 line, covering an arc 50km long, positioned about 18km from the city of Liege. The line was anchored around 3 modern forts (Aubin-Neufchateau, Battice and Tancremont) and supported by 178 bunkers of various sizes, ranging from Armoured Observation Posts (subordinated to forts) to small and large infantry and anti-tank bunkers protecting the roads and intervals between the forts.

The second line of defence was made of the PFL2 and PLF3. PFL3 was made up of 43 bunkers on the Eastern bank of the river Meuse, between the Dutch border and the Belgian town of Argenteau. PFL2 started where PLF3 ended and ran as a 35km long arc, at a distance of around 8km from Liege itself. PFL2 was anchored around 6 modernised Brialmont forts (Barchon, Evegnee, Fleron, Chaudfontaine, Embourg and Boncelles). This line was reinforced by 62 bunkers including 13 Armoured Observation Posts subordinated to the forts of the line.

It is interesting to note that North of PFL3 was the Albert Canal Position, anchored by the fort of Eben Emael and composed of 148 bunkers built all along the bank of the canal, each bunker situated 600 meter apart from one another. This position rarely features on the PFL maps as both the Albert Canal Position and Eben-Emael technically depended on the Antwerp Fortified Position (PFA)!

The third line of defence, called PFL4, was anchored along the Western banks of the river Meuse. 40 bunkers (many built in the pillars of bridges spanning the river) composed the bulk of this line. PFL4 was reinforced at each end by two modernised Brialmont forts, with Pontisse anchoring the line in the North and Flemalle anchoring it in the South.

The roles of the PFL were as follow:

– It was a delaying line, enabling the effective defence of the border area while the Belgian army mobilised and deployed its troops behind its fortifications.

– It was a defensive bridgehead on the Eastern bank of the river Meuse, designed to cover the German border and threaten the axis of communication of the German army in case of a German incursion in the Limburg or Luxembourg provinces and support the defensive actions of the Belgian army in the region: In this case, provide Belgian army troops with a solid prepared and supported fortified line of defence to operate from.

– It was also an offensive bridgehead covering the East bank of the river Meuse designed to help and support a Belgian army surge forward toward the Luxemburg or Limburg provinces. In that particular case, it could simultaneously be used as cover for an eventual retreat of the Belgian army from those zones.

The forts were the central pieces of the PFL. They anchored the successive PFL lines and were designed to interdict access to specific/dedicated areas as well as provide artillery support to the Belgian troops deployed along the successive PFL lines of defence and the intervals between each forts in a way conventional artillery could not (too exposed/vulnerable).

Eben Emael specific mission was to protect the approaches along the Belgo-Dutch border, specifically the bridges over the river Meuse and Canal Albert as well as the Lanaye locks on the river Meuse between Belgium and the Netherlands.

Aubin Neufchateau was to focus its attention on the N608 road running between Vise (Belgium) and Aachen (Germany) as well as interdict the crossroads in the Val Dieu region. It was also to intervene in the area North-West of its position (Warsage / Fourons).

Battice was ordered to interdict traffic along the Aachen-Liege railway and the Aubel-Battice road. The area to its North (Aubel, St Jean-Sart, Henri-Chapelle) and to its South (Petit Rechain, Grand Rechain, Wegimont) were also under its responsibility.

Finally, Tancremont was to keep overwatch on the Theux-Mont road and interdict access throughout the Vesdre and Hogne valleys.

All in all, the Liege Fortified Position was a very strong one. However, it had two major weaknesses: It was insufficiently protected from air attacks due to both the Belgian air force and the Belgian air defences being inadequate. It also had weak flanks: To the North, the line depended on the resilience of the Dutch army to avoid being flanked through the Netherlands. To the South, there wasn’t much to stop the Germans flanking around Liege once passed Tancremont and the PFL1 positions.

Case study: Aubin Neufchateau fortress. Quick overview of what a modern fort looked like.

Aubin is a small “interval” fort. Triangular in shape, situated between two big ones (Eben-Emael to the North and Battice to the South) it was built much deeper than the original Brialmont forts. The fort occupies a surface of 48 hectares which was surrounded by 2600 tetraedres (anti-tank obstacles). The whole fort is built out of reinforced concrete made to resist shelling of up to 420mm in calibre: A typical combat bloc outer walls are 2.5 meters thick while its roof is up to 3.5 meters in thickness. While its combat blocs are visible from the surface, all of its 2.5 kilometres of galleries, the barracks, living quarters, machine rooms, kitchen, hospital and ammunition reserves were all built between 30 and 37 metres underground. Each side of the triangle is roughly 250 meters long with the moat being 15 meters wide and 3 meters deep. The 3 main combat blocs contained within the massif (B3, B1 & B2) are 150 metres apart, so enemy artillery cannot target all of them at once. The dry moat is defended by a single and a double coffer (C1 and C2, respectively) meaning that each of the moat’s three sides are covered by a coffer. The access road running alongside the fort is overlooked by a block equipped with two 47mm anti-tank guns in cupolas (CIII). BIII is the peacetime entrance. BI and BII are the gun turret blocs, each equipped with a twin 75mm guns. BP is the wartime entrance. It also functions as an air intake / ventilation bloc. O is an observation / air intake bloc and also contains the fort’s hidden emergency exit. Each combat bloc linking the fort to the surface is equipped with “explosives shelves”: Recesses made at the base of each bloc’ stair case and designed to hold explosive charges that could be detonated. In case of combat bloc being breached form the outside, the defenders could detonate the charges at the base of said bloc, condemning it and preventing the assailants from penetrating inside the fort itself. CIII, BP and O are the only three blocs that are situated beyond the moat and outer walls. The fort had a garrison of 566 men and officers. Finally, Aubin had 4 dedicated Armoured Observation Bunkers placed at strategic locations within its area of operation. Those bunkers would be its ears and eyes and were all linked to the fort by phone lines.

Aubin Fortress

Aubin was supposed to operate independently (without being ressuplied) for a month. To that effect, it was equipped with 4 diesel engines supplying power and hot water (for both the central heating and the shower room). The garrison was sheltered in underground barracks, composed of bedrooms, washrooms and toilets, a kitchen, a chapel and a medical centre including a hospital and an operating theatre. There were two wells equipped with a water filtration system. There was also an air filtration system for the barracks as the fort was ventilated and its combat blocs were pressurised.

The fort’s main armament was composed of four 75mm guns in two turrets (effective range:10.1km), three 81mm mortars in casemates (effective range: 3.6km), seven machine gun cupolas, four machine gun embrasures, two automatic rifle ports, two 47mm anti-tank gun cupolas and three anti-tank gun embrasures as well as 6 searchlights. It also had a complement of six AA machine guns.

The ammunition reserves on the first day of the war were as follow:

  • 11.200 x 75mm shells (3.000 shrapnel, 7.000 HE, 1.200 grapeshots shells).
  • 6.000 x 81mm bombs for the mortars.
  • 1.500 x 47mm shells (360 Anti-tank and 1.140 Anti-personnel)
  • 720 Mills grenades (hand grenades)
  • 315.000 x 7.65mm cartridges for Maxim machine guns, automatic rifles and rifles.
  • 27 FN Mle 1930 automatic rifles
  • 433 Mauser rifles

Furthermore, the fort had been supplied with 8,000 litres of diesel for its engines, food and medical supplies.

Follow our page between the 10th of May and the 21st of May as we translate the Aubin fortress’ journal day by day, enabling you to relive the furious fighting that took place during its 12 days siege in May 1940.

Renaud Mayers
Currently working on behalf of the Belgian Ministry of Defence, thanks to my knowledge in WWII and other areas. Working in two WWII era fortresses still belonging to the Army.

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