Petit Ouvrage Immerhof filled in the gap between the gros ouvrages at Molvange (to the west) and Soetrich to the east. Its main offensive weapon was an 81mm mortar, particularly useful for filling in any dead ground between the two major forts. This section of the Maginot Line provided protection for the iron and coal mines that surrounded Thionville. Immerhof saw little action in the war and the garrison left on 30 June 1940 after the French armistice of 25 June.
The fort was then occupied in turn by the Germans, Americans, French and NATO before being bought by the nearby town of Hettange-Grande. The local group of volunteers have done an exceptional job in restoring the fort. Our guides were dressed in period army uniforms and their relative sizes meant they were known as ‘Monsieur Gros Maginot’ and ‘Monsieur Petit Maginot’.
Outside the main entrance block a small section of barbed wire entanglement remained, as did the stumps of the original anti-tank defences. The hooks above the entrance and in front of the block that supported the camouflage netting were very robust (at many forts they are just bent rebar). We were told one veteran recalled riding down the steel mesh netting on a motorbike before the German invasion. The brackets that supported the fort’s radio aerials were also present - they would have been as high as possible while still protected by the camouflage.
Once inside the fort, it felt immediately different from other Maginot forts. Because it was built by cut and cover, the corridors are flat-roofed rather than arched and the whole fort is on a single level. The paint work and signage is in exceptional condition, and the feel was of a structure recently vacated rather than an 85 year old relic.
Our first stop was in the casemate that protected the main entrance, equipped with a pair of dual machine guns, one of which could be swapped out and replaced with an anti-tank weapon. We had a detailed explanation of how the machine guns could be fired together or separately to reduce overheating; the barrels could be removed and immersed in water in extreme circumstances. The magazine for the machine guns was a circular clip-on design, holding 100 rounds which wouldn’t last long at 650 rounds per minute. Because of its shape, the magazine was nicknamed a camembert. The entrance block also held the usual observation/light weapon cupolas.
Moving along the roughly Y-shaped corridor, we entered the main turret for the fort’s 81mm twin mortars. We were told that this was the only remaining such turret that operated both manually and electrically although disappointingly neither method was demonstrated. The weapon was fully retractable and weighed around 150 tonnes.
The firing rate was up to 15 rounds per minute; the range of the weapon was a comparatively modest 4km (Immerhof is about 4km from the Luxembourg border and it was general practice for the weapons not to fire across International borders to ensure they could not be classified as offensive weapons). The mortars could either have contact fuses or be set for air detonation. We were told that the turret could be mechanically ‘programmed’ to operate a barrage - either advancing or retreating. The fort allegedly used wild dogs for target practice which conjured up a rather grisly image.
We had an extensive tour of the Barrack Block, which seemed quite extensive for the 200 occupants. The usual three-tier bunks were adjacent to washrooms, with more comfortable quarters for NCOs and Officers. The Command Post had been turned into a small museum which included a 3D model of this sector of the line, showing the fort’s position in a valley plain, supported by heavier artillery on the high ground to each side.
Other services included a kitchen (converted to electric operation during NATO days), food stores and a small infirmary. The usual well was much shallower than usual. The fort only suffered one fatality during the war when 20 year-old Corporal André Rabu was killed on patrol outside the fort on 14 June 1940. He was brought back to the fort but died in the infirmary as his femoral artillery (sic) had been severed by shrapnel.
On the plant side, twin generators provided electrical power - they had been replaced in NATO days but one of the volunteers had spent months refurbishing two authentic examples which are now in their place. Filter rooms and air-handling provided clean air with a slight over-pressure. Workshops (still in use by the volunteers) included a fully equipped forge, located surprisingly close to the main turret.