La Coupole

La Coupole (English: The Dome), codenamed Bauvorhaben 21 (Building Project 21), Schotterwerk Nordwest (Northwest Gravel Works) or Wizernes,^[3] is a Second World War bunker complex built by the forces of Nazi Germany between 1943 and 1944 to serve as a launch base for V-2 rockets against London and southern England. It is situated in the commune of Helfaut in the Pas-de-Calais region of northern France, about 5 kilometres (3.1 mi) from Saint-Omer.

Constructed in the side of a disused chalk quarry, the complex comprised an immense concrete dome, to which its modern name refers, above a network of tunnels that were to house the launch facilities and crew quarters. The facility was intended to store a large stockpile of V-2s, warheads and fuel and to be able to launch missiles against London and southern England at a high daily rate. Heavy secret weapons sites like Wizernes, Watten, Mimoyecques and the Wasserwerks of St Pol, Desvres, were collectively called by the Organization Todt the "Special Constructions", Sonderbauten in German.^[4]

However, due to repeated heavy bombing by Allied forces carried out as part of Operation Crossbow, the Germans were unable to complete the construction works and the complex never entered service. It was captured by the Canadian Army in September 1944 and was subsequently abandoned. The complex remained derelict and abandoned until the mid-1990s. In 1997 it opened to the public for the first time after being redeveloped into a museum. The tunnels and the main exhibition area under the dome tell the story of the German occupation of France during World War II, the V-weapons and the history of space exploration.

Background

The deployment of the V-2 missile required large quantities of liquid oxygen (LOX) – more, in fact, than was available from existing production sites in Germany and the occupied countries. New sources of LOX were required, situated close to the missile launching sites to reduce as far as possible the loss of propellant through evaporation. The missile's operational range of 320 kilometres (200 mi) meant that the launch sites had to be located fairly close to the English Channel or southern North Sea coasts, in northern France, Belgium or the western Netherlands.^[5]

Because of the complexity of the missile and the need for extensive testing prior to launch, the V-2's designers at the Peenemünde Army Research Center favoured using heavily defended fixed sites where the missiles could be stored, armed, fueled from an on-site LOX production plant and launched. This was opposed by the German Army and the V-2 project's head, Major-General Walter Dornberger, who were concerned that the sites would be vulnerable to aerial attack by the Allies. The Army's preferred option was to use Meillerwagens, mobile firing batteries, which presented a much smaller target for the Allied air forces.^[5]

The Army was nonetheless overruled in March 1943 by Adolf Hitler. His long-standing preference for huge, grandiose constructions led him to order the construction of a massive bunker (now known as the Blockhaus d'Éperlecques) in the Forest of Éperlecques near Watten, north of Saint-Omer. The bunker was soon spotted by Allied reconnaissance and on 27 August 1943, a raid by 187 B-17 bombers wrecked the site before it could be completed. A surviving portion was re-used by the Germans as a LOX production facility.^[5]

Design and location

The successful attack against the Watten bunker forced the Germans to find an alternative location for a launch site nearby. An old quarry situated between the villages of Helfaut and Wizernes, south-west of Saint-Omer some 12 kilometres (7.5 mi) south of the Watten bunker, had already been designated for use to store missiles in tunnels bored into the chalk hillside.^[6] It was located near the Aa river alongside the Boulogne–Saint-Omer railway line, about three-quarters of a mile (1 km) from Wizernes station. The Germans had already undertaken major work in August 1943 to lay extensive railway sidings to connect the quarry to the main line.^[7]

On 30 September 1943, Hitler met with Albert Speer, the Minister of Armaments and War Production, and Franz Xaver Dorsch, the chief engineer of the Todt Organisation, 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, 5 feet (1.5 m) thick, 71 metres (233 ft) 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 7 kilometres (4.3 mi) 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.^[6]

A standard gauge railway tunnel, codenamed Ida, was to be built on a curving path that would connect it with both the east- and west-bound main line railway, allowing trains to run straight through the complex without needing to reverse or be turned around. This would serve as the main unloading station, where missiles and supplies would be offloaded onto trolleys that would transport them into the connecting galleries Mathilde and Hugo. Hugo connected in turn with Sophie, a dead-end railway tunnel branching from the main line into Ida. Each of the main tunnels had a number of unnamed side tunnels of the same dimensions as the main tunnels and up to 90 metres (300 ft) long. The central feature of the complex was a huge octagonal chamber directly under the dome. It was never completed but would have been 41 metres (135 ft) in diameter and up to 33 metres (108 ft) high. A number of intermediate floors, possibly as many as ten, would have been built up the sides of the chamber.^[9]

The western side of the chamber opened onto two tall passageways called Gustav and Gretchen. Each was to have been protected by bomb-proof doors made of steel and concrete. The passageways were to be 4 metres (13 ft) wide and at least 17 metres (56 ft) high and were angled in a Y-shape, exiting into the quarry. Open-air platforms for launching rockets would have been situated at the end of each passageway. The two passageways were angled at 64° 50' and 99° 50' west of north respectively – not aligned with any probable target but merely permitting the rockets to be transported to sufficiently widely separated launch pads.^[10]

The facility was designed, as was its predecessor at Watten, to receive, process and launch V-2 rockets at a high rate. Trains carrying V-2s would enter the heart of the complex through the Ida rail tunnel, where they would be unloaded. A large number of V-2s could be stored in the side tunnels; LOX would also be produced on-site ready for use. When the time came, the rockets would be moved into the octagonal preparation chamber where they would be lifted to a vertical position for fueling and arming. From there they would be transported on motorised launch carriages through the Gustav and Gretchen passageways and out to the launch pads, ready to be fired.^[11]

The priority target for the V-2s was London, 188 kilometres (117 mi) away, that Hitler wanted to see pulverised by the end of 1943.^[4] The Allies were alarmed when a photo interpreter found out that part of the complex was aligned within half a degree of the Great Circle bearing on New York, though Albert Speer denied after the war that there had been any intention of using Wizernes as a launch site for intercontinental missiles such as the planned A10.^[12]

Although physically separate, another facility built in nearby Roquetoire was an integral part of the Wizernes complex. Umspannwerk C was built to house a Leitstrahl radio command guidance system which could be used to send course corrections to missiles launched from Wizernes to fine-tune their trajectory during the launch phase.^[13]

Construction

After the Watten bunker had been put out of commission, Hitler agreed to convert the Wizernes storage bunker to a launching site. in October 1943, Speer noted that "he [the Führer] is not convinced that the site will ever be finished".^[14] Construction work began in October 1943 and the building of the dome commenced in November. It proved a slow process because of constant air-raid warnings, which stopped work 229 times in May 1944 alone. The constant delays were a source of major frustration as they meant that the Todt Organisation could not provide a completion date. Dornberger's representative commented: "This means that no date can be set for the specialised launching gear and machinery to be installed. General Dornberger has asked Field Marshal von Rundstedt to decide whether it would not be better to abandon the whole project."^[15]

Dornberger reported that he considered the structure to be useless. However, this was contradicted by Todt engineers and fortification experts, and by Hitler himself, whom Speer recorded was "infuriated by this frivolous way of reporting things."^[15] In response to Hitler's desire to see the site completed the workforce was built up substantially from 1,100 in April 1944 to nearly 1,400 by June.^[16] About 60% of the workers were Germans; skilled workers, such as miners from Westphalia, were recruited to excavate the tunnels and build the dome.^[17] The remainder were principally Frenchmen conscripted by the Service du travail obligatoire (STO), plus Soviet prisoners of war.^[6][18] The project was overseen by several large German construction companies, with Philip Holzman A.G. of Frankfurt am Main and the Grossdeutsche Schachtbau and Tierbohr GmbH serving as the chief contractors.^[19]

One of the most difficult challenges faced by the Germans was that of how to construct the great dome while under regular air attack. The dome's designer, Todt Organisation engineer Werner Flos, hit upon the idea of building the dome first, flat upon the ground, and then excavating the soil underneath it 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 84 metres (276 ft). The dome was built within this trench and the galleries and octagonal preparation chamber were excavated below.^[7][20]

As an additional bomb-proofing method, the dome was surrounded by a bomb-proof "skirt" or Zerschellerplatte of steel-reinforced concrete, 14 metres (46 ft) wide and 2 metres (6.6 ft) thick. This was supported by a series of buttresses, which were not tied into the dome itself, above the entrances to the Gustav and Gretchen tunnels. Another concrete structure was tied into the skirt to the northwest 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.^[21] A Decauville narrow-gauge railway was installed on the quarry floor to transport supplies from the main line to the construction site.^[22]

A cube-shaped concrete building was constructed on the top of the hill, next to the dome. This was intended to be used as the bomb-proof outlet for a ventilation and air conditioning shaft – an essential element for a facility where dangerous and explosive gases were expected to be used in large quantities on a daily basis. It was never finished and when the Allies captured the site they found that the ventilation shaft had not been fully excavated. The building survived the bombing intact and is still prominently visible today.^[21]

Unlike its sister site at Watten, there was no on-site power plant; electricity at Wizernes was provided by a connection to the main electric grid, with consumption estimated at between 5,000–6,000 kVA.^[19]

Discovery and Allied attacks

The Allies became aware of the Wizernes site in August 1943 when the Germans began laying extensive new rail sidings which were spotted by RAF reconnaissance flights.^[7] In November 1943, the Allied Central Interpretation Unit reported that the Germans had begun constructing the concrete dome and were undertaking tunnelling works in the east face of the quarry. However, it was not until the following March that the Allies added the site to the list of targets for Operation Crossbow, the ongoing bombing campaign against V-weapon sites that had already wrecked 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.^[13] The bombings caused destruction across a wide area, killing 55 residents of the nearby village of Helfault.^[23]

Conventional bombing raids only achieved a single bomb hit the dome itself, causing negligible damage. However, in June and July 1944 the RAF began attacking the site with 6-ton ground-penetrating Tallboy bombs.^[13] 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."^[24] His staff reported on 28 July 1944 that, although not hit by the Tallboys, "the whole area around has been so churned up that it is unapproachable, and the bunker is jeopardised from underneath."^[25]

In May 1944, the 953 (Semi-Mobile) Artillery Detachment started Abteilungen (firing detachment) training at Blizna in southeastern Poland for operations at Wizernes. Consisting of one technical and two operational batteries, the detachment was expected to launch up to 50 rockets daily from Wizernes.^[26] However, they never got the chance. On 3 July 1944, the Oberkommando West gave permission to stop construction at the heavily damaged Watten and Wizernes sites. On 18 July 1944, Hitler abandoned plans for launching V-2s from bunkers^[27] and authorized the downsizing of the Wizernes bunker into a LOX production facility.^[28] However, these plans were overtaken by the liberation of Northern France consecutive to the Normandy landings. The site was finally abandoned and inspected by British engineers on 5 September.^[29]

Post war investigations

Shortly after the Wizernes site had been captured in September 1944, Duncan Sandys, the head of the British "Crossbow Committee" investigating the V-weapons programme, ordered the constitution of a Technical Inter-Services Mission under Colonel T.R.B. Sanders. It was given the task of investigating the sites at Mimoyecques, Siracourt, Watten, and Wizernes, collectively known to the Allies as the "Heavy Crossbow" sites. Sanders' report was submitted to the War Cabinet on 19 March 1945.^[30]

The purpose of the Wizernes site had been unclear prior to its capture but Sanders 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. Sander's 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 17 metres (56 ft) and 24 metres (79 ft) in length and 4 metres (13 ft) in breadth.^[31] (This was substantially larger than the V-2, which measured 14 metres (46 ft) long and 3.55 metres (11.6 ft) wide.) Two witnesses interviewed by the Sanders team reported "an intention of firing a projectile 18 metres long."^[19] 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."^{[19][Notes 1]} 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.^[22]

The site reverted to private ownership after the war. As the quarry had long since been worked out, it was abandoned.^[20] The tunnels were not destroyed but were sealed off, though at some point they were reopened by local people and could be entered; the octagon remained sealed off with a ceiling-to-floor barricade. The quarry itself remained in almost the same condition as it had been in 1944, with sections of railway track still in place on the quarry floor. The hospital section remained relatively intact and was used by the local gendarmes as a shooting range.^[22]

Museum of La Coupole

In 1986, the Espace Naturel Régional in Lille earmarked 10 million FF to develop the site as a tourist attraction for the Nord-Pas-de-Calais region with the intention of establishing a Second World War 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.^[20]

Local historian Yves le Maner was charged with the task of developing the project while a feasibility study was conducted into the possibility of completing some of the original excavation work to make the site safe for public access. The plans were approved in 1993 and the site was bought by the Commune de Helfaut. The following year, the Conseil Général du Pas-de-Calais acquired the site. The 69 million FF project (£7.5 million at 1997 prices) was largely underwritten by the Conseil Général, which provided 35 million FF, with another 17 million FF coming from the regional council. The European Community provided a further 12 million, the French State provided 3 million FF and the Saint-Omer municipal administration funded the remaining 1 million FF; a number of private shareholders were also involved. The Societé d'Equipement du Pas-de-Calais was contracted to carry out the development work, which involved excavating a further two metres (six feet) beneath the dome, clearing out and completing the unfinished concreting of some of the tunnels, building an exhibition centre and car park in the quarry floor and installing a lift to carry visitors up from the octagon to the dome.^[1]

The museum opened in May 1997. The main exhibition area is housed beneath the dome and focuses on three main issues: the story of the V-weapons; life in occupied France; and the conquest of space after the war. It presents audio-visual displays in English, French, Dutch and German as well as a large number of original artifacts including a V-1 provided by the Science Museum in London and a V-2 provided by the Smithsonian Institution in Washington, D.C.^[1] In 2011, the museum welcomed 120,000 visitors.^[32] Since 2010, the museum has also managed the V-3 site of the Fortress of Mimoyecques.^[33]

Air raids on the Wizernes site

Notes

References

Citations

Bibliography

External links

• Media related to [//commons.wikimedia.org/wiki/Category:Coupole_d%27Helfaut La Coupole] at Wikimedia Commons
• Official site of La Coupole
• Kelly, Jon (13 May 2011). "Operation Crossbow: How 3D glasses helped defeat Hitler". BBC Documentary. BBC. http://www.bbc.co.uk/news/magazine-13359064. Retrieved 2011-08-17. 
• Patrimoine architectural et mobilier en Bretagne. "Wizernes La Coupole Schotterwerk Nord West (SNW) : Base V2 (actuellement musée)" (in French). Patrimoine architectural et mobilier en Bretagne. http://patrimoine.region-bretagne.fr/main.xsp?execute=show_document&id=MERIMEEIA62000001. Retrieved 20 June 2011.