It is estimated that it would have required 200,000 tons of concrete as well as the 20,000 tons of steel to complete the bunker.
The Blockhaus d’Eperlecques is a remarkable piece of World War II history. In March 1943 Germany started building this giant bunker in northwest France. Its location was close to the small town of Watten so it is also sometimes called the Watten Bunker.
The bunker was never completed as the Germans intended. It was discovered while construction was still in progress and was repeatedly bombed by the Allies.
After successive bombings, the Germans moved their most of the operations to another location. The bunker has been preserved as a historic monument and today it is part of a private museum.
Secret Missile Launching Site
The Blockhouse d’Eperlecques was intended to serve two main purposes. One was that it would be used as a factory to produce liquid oxygen. During the Second World War, liquid oxygen was used as a propellant to launch missiles.
More importantly, the bunker would also be a site for launching missiles. It would be able to store 100 A-4 ballistic missiles and would be able to launch up to 36 missiles a day. The intended targets of these missiles were London and the south of England. The bunker’s location in northwest France brought this area within range of the missiles, as it was only 110 miles (177km) from London.
The location was also ideal because it was on the route of two railway lines running between St Omer and Calais. This would make it easy to bring materials and missiles to the bunker. The location was well hidden because of the surrounding Eperlecques Forest.
The area was also well stocked in the resources needed to construct a major well-defended building. There were sand and gravel quarries nearby as well as a cement factory. Other construction materials could be brought to the site by rail.
It is estimated that it would have required 200,000 tons of concrete as well as the 20,000 tons of steel to complete the bunker. Both the size and the strength of the building made it an enormous undertaking.
And of course, this all had to be done without being discovered by the Allies. The project was given the code name Kraftwerk Nord West (Northwest Power Plant) to keep its true purpose as a missile launch site hidden.
Building Work Begins
The construction of the bunker was supervised by the Germans, but the hard labor was done by French workers conscripted under the Service du Travail Obligatoire. This was a compulsory work service initiated by the Vichy Government. It resulted in thousands of French workers being used as forced labor, mostly in Germany but also in other parts of occupied Europe.
As so many men were needed to build this giant construction more recruits were brought in from Prisoner of War camps. These included Belgian, Dutch, Polish, and Soviet as well as French prisoners of war.
The building of the Blockhaus involved somewhere between 2,000-3,000 men. They were forced to work under appalling conditions. Building went on 24 hours a day, 7 days a week. Giant flood lamps were used to keep the men working through the night. They worked 12-hour shifts and only got a 20-minute break during their shift.
Under these conditions, it was not surprising that the workers sometimes became ill or got injured. But they received no medical attention and many died. Those who survived their injuries but were unable to work were sent back to their camps.
Discovery and Destruction
It was no easy task to keep a construction project on that scale a secret, and it wasn’t long before suspicions were aroused. In April 1943 the Allies became aware of activity in the area and set out to investigate.
The Allies did not know what the Germans planned to use the bunker for, but given the amount of effort that was going into its construction, they realized it must be a pretty important project. They decided that the safest option was to assume the worst and destroy it before the Germans put their plan—whatever that might be—into action.
The first attack took place on 27 August 1943. It was carried out by a B-17 Flying Fortress from the US 8th Air Force. The attack was planned precisely so that it would strike while a new batch of concrete was still wet, causing it to spread everywhere. It then set firm, making a large part of the building completely unusable.
The timing had also been planned to coincide with the break between shifts in order to minimize casualties. But because of the pressure to get through the day’s work, the shift pattern had been changed. As a result, the attack killed hundreds of workers.
The Germans did not give up the facility right away. Although it could no longer be used as a missile launching site, they did continue to use it to produce the liquid oxygen they required.
The German engineers came up with a way of protecting the building while it was still being constructed. They designed a roof like a huge tortoise shell which would cover the building while repairs and further construction work took place.
As building continued, the roof would gradually be raised until it reached its final height. At 16 feet (5 m) thick, the roof was thought to be strong enough to withstand future air raids.
However, the Allies returned with further attacks. The final decisive air raid took place in July 1944 when they dropped a Tallboy bomb. This was one of the recently developed earthquake bombs. The bunker received irreparable damage.
Most of the work of producing liquid oxygen was then moved to another site. By the time the site was finally captured on 4 September 1944, it had been abandoned. The pumps which had been used to keep water out had been turned off and the bunker had flooded.
The Blockhaus Museum
Today you can visit this site. It is an excellent example of a major military installation and was recognized as a historic monument in France in 1986. It has become part of a private museum, which offers a guided tour to let you walk around and explore this fascinating piece of military archaeology.