The Bombing of the Major V-Weapon Sites – Wizernes and La Coupole

Blown Periphery, Going Postal
The reinforced concrete dome of La Coupole today

As discussed in the previous article, the successful air attacks against the Watten bunker forced the German Army to find an alternative location for a V-2 missile launch site nearby. They had already taken possession of an old quarry between the villages of Helfaut and Wizernes, south-west of Saint-Omer and some 7.5 miles south of the Watten bunker. The site was near the Aa river alongside the Boulogne–Saint-Omer railway line and about 0.62 miles from Wizernes station. The quarry had been designated for use as a missile storage depot where V-2s would be housed in tunnels bored into the chalk hillside before being transported for launching. The Germans undertook major work in August 1943 to lay extensive railway sidings to connect the quarry to the main line.

Constructed in the side of a disused chalk quarry, the most prominent feature of the complex was and still is an immense concrete dome, to which its modern name refers. It was built above a network of tunnels housing storage areas, launch facilities and crew quarters. The facility was designed to store a large stockpile of V-2s, warheads and fuel and was intended to launch V-2s on an industrial scale. Dozens of missiles a day were to be fuelled, prepared and launched in rapid sequence against London and southern England.

On 30th September 1943, Hitler met with Albert Speer, the Minister of Armaments and War Production, and Franz Xaver Dorsch, the chief engineer of the Organisation Todt, to discuss plans for a replacement for the out-of-commission Watten facility. Dorsch proposed to transform the Wizernes depot into a vast bomb-proof underground complex that would require a million tons of concrete to build. It would be constructed within a network of tunnels to be dug inside the hillside at the edge of the quarry. A concrete dome, 16 feet thick 233 feet in diameter and weighing 55,000 tons, would be built over the top of the central part of the facility to protect it from Allied bombing. Beneath it, about 4.3 miles of tunnels were to be dug into the chalk hillside to accommodate workshops, storerooms, fuel supplies, a LOX manufacturing plant, generators, barracks and a hospital; though not for the unfortunate slaves who would do the digging.

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Map of the Wizernes site with La Coupole central in the plan

The V-2s would be transported into the site by its own railway, and unloaded and stored is the maze of tunnels. Liquid Oxygen (LOX) was produced on site and the rockets would be moved to the octagonal preparation chamber under La Coupole and moved into an upright position for fuelling and arming. The rockets would then be moved onto a motorised launch platform and moved through the Gustav and Gretchen passageways. The launch pads were located at the end of the track on the floor of the quarry, from where the missiles would be fired.

The priority target for the V-2s was London, the centre of which was 117 miles away. Hitler wanted London to be pounded into submission by the end of 1943. Additionally, work was already underway in 1943 to produce a much larger A-10 intercontinental ballistic missile, the so-called “America Rocket,” and the Wizernes complex had the capacity to launch them. A separate facility was built at Roquetoire to house a Leitstrahl radio command guidance system, to fine-tune the trajectory of the rockets in-flight, launched from Wizernes.

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Concept of operations. The Octagon and rail tracks to external launch pads

The Allies noticed the construction activity at Wizernes in mid-1943, as a result of the pre-Overlord photograph reconnaissance campaign. A sharp-eyed WAAF photographic interpreter noticed the construction of a railway, leading from the main line to a quarry that was extensively covered with camouflage netting. The construction of the huge concrete dome (La Coupole) was started in November 1943 and tunnelling into the cliff face began in the December of that year. The building works were greatly hindered by the constant air-raid warnings, which stopped work 229 times in May 1944 alone. The Allies, not knowing what the construction was for, decided that if the Germans were going to the trouble of building it, they would bomb it.

In response to Hitler’s desire to see the site completed the workforce was expanded substantially from 1,100 in April 1944 to nearly 1,400 by June and around 60% of the work force were skilled German labourers and miners. The remainder were French, recruited by the Service du travail obligatoire (STO) and Soviet POWs. The German construction companies were Philipp Holzman A.G. of Frankfurt am Main and the Grossdeutsche Schachtbau and Tiefbohr GmbH.

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Reconnaissance photograph of La Coupole, taken by a Mosquito at low-level

The regular air attacks made the construction of the dome difficult for the German engineers. The dome’s designer, Todt Organisation engineer Werner Flos, devised a plan under which the dome would be built first, flat upon the ground, and the soil underneath it would be excavated so that the construction works below would be protected against aerial attacks. A circular trench was excavated on the top of the hill above the quarry to an outside diameter of 276 feet. The dome was built within this trench and the galleries and octagonal preparation chamber were excavated below. The dome was also provided with a bomb-proof skirt of steel-reinforced concrete, supported by external buttresses (Zerschellerplatte). Another concrete structure was tied into the skirt to the north-west of the dome, which was perhaps intended for use as an observation and control tower. A separate underground building was constructed on the western side of the quarry to serve as a hospital and as offices for the engineers. A Decauville narrow-gauge railway was installed on the quarry floor to transport supplies from the main line to the construction site.

A cube-shaped concrete building was erected on top of the hill next to the dome, for the use as an outlet for the ventilation and air conditioning shaft. This was essential to vent the poisonous and potentially explosive gasses that would build up in the galleries. When the Allies inspected the site after it was captured in 1945, the ventilation system hadn’t been completed. They also discovered that the site did not have its own power station. Instead it was connected to the main electric grid, with power consumption estimated at between 5,000 and 6,000 kVA.

Allied Air Attacks

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Lancaster over Wizernes. The white streaks on the wings are from the high lead content of the 100 octane fuel
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Tallboy bomb dropped on Watten bunker 1944

Flown back from occupied Europe in late 1943, a Belgian, Jacques de Duve, supported by German opponents of military rocketry, informed MI5 about the existence of a rocket production site in Saint-Omer. MI5 did not believe Jacques de Duve, who was interned for the rest of the war in Latchmere House and I feel a growing sense of incredulity and have to ask, whose side was MI5 on? The photographs belied the Intelligence Services’ inertia, but it wasn’t until March of 1944 that the Wizernes site was added to the priority Crossbow targeting list, which had already destroyed the Watten bunker and numerous V-1 launching sites. Over the next few months, the USAAF and RAF carried out 16 air raids involving 811 bombers that dropped some 4,260 tons of bombs. The bombing caused destruction across a wide area, killing 55 residents of the nearby village of Helfault.

Conventional bombing raids only achieved a single bomb hit on the dome itself, causing negligible damage. However, in June and July 1944 the RAF began attacking the site with 12,000 pounds, ground-penetrating Tallboy bombs. The external construction works were completely wrecked by the bombing and one Tallboy landed just beside the dome, blowing out the entire quarry cliff face and burying the entrances to the Gustav and Gretchen tunnels. The entrance to Sophie was also buried, leaving Ida as the only entrance to the facility. The dome was unscathed but the buttresses supporting the protective Zerschellerplatte were dislodged and slid partway down into the quarry. Serious damage was also caused to the tunnels beneath the dome. The damage made it impossible to continue work on the site. Dornberger complained: “Persistent air attack with heavy and super-heavy bombs so battered the rock all around that in the spring of 1944 landslides made further work impossible.” His staff reported on 28 July 1944 that, although the dome had not been hit by the Tallboys, “the whole area around has been so churned up that it is unapproachable, and the bunker is jeopardised from underneath.”

Blown Periphery, Going Postal
12,000 lb Tallboy lifted from the bomb dump for loading onto a strengthened bomb trolley

Air raids on the Wizernes site

11 March 1944 51 Consolidated B-24 Liberators of the 2d Bombardment Division’s 44th and 93d Heavy Bombardment groups attacked Wizernes using blind-bombing techniques due to thick overcast, dropping 127 tons of bombs.
19 March 1944 152 Martin B-26 Marauders of IX Bomber Command attacked V-weapon sites around Saint-Omer.
26 March 1944 500 heavy bombers of the 8th Air Force attacked a total of 16 V-weapon sites in northern France, including Wizernes, dropping 1,271 tons of bombs. Allied losses were four Boeing B-17 Flying Fortresses and one B-24; a further 236 bombers were damaged by enemy fire.
17 April 1944 14 B-24 Liberators and five pathfinder aircraft used an experimental bombing technique to attack Wizernes.
25 April 1944 27 B-24 Liberators from 2d Bombardment Division bombed Wizernes in a special test of new pathfinding equipment.
3 May 1944 47 B-24 Liberators escorted by 101 fighters from VIII Fighter Command attacked Wizernes using blind-bombing techniques.
20 June 1944 17 Avro Lancasters and 3 De Havilland Mosquito of No 617 Squadron attempted to attack Wizernes but were forced to abort by cloud cover over the target.
22 June 1944 A second 617 Squadron attack on Wizernes was again thwarted by cloud cover.
24 June 1944 617 Squadron returned to Wizernes with 16 Lancasters and 2 Mosquitos, losing one Lancaster to anti-aircraft fire.  Several Tallboy bombs were dropped but failed to cause much damage.
28 June 1944 103 Handley Page Halifaxes and 5 Mosquitos from No. 4 Group and 2 Lancasters of the Pathfinder Force attacked Wizernes without loss.
17 July 1944 72 Halifaxes, 28 Stirlings, 20 Lancasters, 11 Mosquitos and 1 North American Mustang attacked three V-weapons sites including Wizernes, which was attacked with a dozen Tallboys.  The attack caused severe damage to the site and buried the entrances to the launch tunnels Gustav and Gretchen. The site was abandoned a few weeks later.
20 July 1944 174 Lancasters, 165 Halifaxes and 30 Mosquitos attacked V-1 launching sites and the Wizernes site.
20/21 July 1944 54 Halifaxes, 23 Lancasters and 10 Mosquitos attacked V-weapon sites at Ardouval and Wizernes, but no bombs were dropped at Wizernes due to bad weather.
4 August 1944 An experimental Operation Aphrodite attack using remotely controlled B-17 Flying Fortress drones packed with explosives failed when they overshot Wizernes by 2,000 feet.

The purpose of the Wizernes site had been unclear prior to its capture but Sanders of the Crossbow Committee was able to deduce its connection with the V-2 from the dimensions of the complex and some intelligence information that his team had been able to retrieve. Sanders’ report concluded that it was “an assembly site for long projectiles most conveniently handled and prepared in a vertical position”. He conjectured the approximate length of the projectiles from the height of the Gustav and Gretchen tunnels, though he noted that there was some doubt about the height of the doors at the tunnel entrances. Segments of the doors had been recovered from a storage dump near Watten railway station, but were incomplete. Judging from the size of the tunnel entrance, the maximum size of the projectile could have been between 56 feet and 79 feet in length and 13 feet in breadth. (This was substantially larger than the V-2, which measured 46 feet long and 11.6 feet wide). Two witnesses interviewed by the Sanders team reported “an intention of firing a projectile 60 foot long.” Sanders noted that “the dimensions of the site make it suitable for the A.4 (V-2) rocket, but the possibility of a new rocket up to half as long again as the A.4 and twice the weight cannot be ruled out.” He concluded that much of the site was becoming unsafe due to the progressive collapse of timbering and recommended that the tunnels and workings under the dome should be destroyed to prevent subsequent accidents or misuse.

In 1986, the Espace Naturel Régional in Lille earmarked 10 million francs to develop the site as a tourist attraction for the Nord-Pas-de-Calais region with the intention of establishing a World War II museum there. The plan was publicised in a special open weekend on 20–21 June 1987, attended by over 20,000 people, in which the dome’s designer Werner Flos met Professor Reginald Victor Jones, a surviving member of the “Crossbow Committee”, at Wizernes. The Ida tunnel and side chambers were opened to the public and used for an audio-visual exhibition of the site’s history.

The site is well worth a visit if you’re waiting for a ferry. Visitors enter and leave through the Ida railway tunnel, though the rails have been removed and the floor levelled. Short branch tunnels lead off on either side; originally used for storage, they now display wartime objects. There is a rather claustrophobic lift ride up to inside La Coupole, where there are exhibits of the V-1 and V-2 and the rocketry programme. There is an area devoted to Le Resistance (naturally) but very little is mentioned of the RAF raid (when I was there) that finally destroyed the complex and the Tallboy bombs that lifted La Coupole and set it back down at an obvious angle.

La Coupole Website

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Mock-up of a V-1 Manned Flying Bomb flown by Hanna Reitsch to discover the weapon’s gyro-stabilisation problem. Located in the entry hall

 

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