The giant bunker (blockhaus) at Eperlecques in many ways mirrors that of Wizernes (La Coupole), being designed to store, prepare and launch the German V2 rockets. The V2 was powered by a combination of liquid oxygen and alcohol so in addition the site was designed for the manufacture and storage of liquid oxygen. The site was chosen to have good communication by rail and canal and to be outside the range of Naval guns; large amounts of power were needed and high voltage power lines were nearby. The project was codenamed Kraftwerk Nord West (KNW) and the liquid oxygen production was to the south of the site with the launch bunker to the north.
Construction commenced in March 1943, labour being supplied by thousands of slave workers. 120,000 tonnes of concrete were required and the raw materials were delivered by barge via the nearby canal and a narrow-gauge railway. In order to reduce the vulnerability to bombing attacks the five metre thick roof of the liquid oxygen bunker was built first and then gradually lifted into place using hydraulic jacks while the walls were built beneath. At the time the local population believed a large power station was being constructed.
The site was first detected by photo-reconnaisance in May 1943 but its purpose was not immediately understood. Later in the same year Operation Crossbow began – the Allied programme to detect and destroy the V-weapon threat. The first attack on Eperlecques was on 27 August when 187 US Flying Fortresses dropped over 350 tonnes of bombs. Concrete in the northerly section had recently been poured and the devastation was immense. At some stage after these attacks it was decided to continue with the liquid oxygen factory alone. Although compressors were installed, the site was never operational; attacks from June 1944 using the 5 ton Tallboy are believed to have damaged the pipework and the site was abandoned in July. The bunker was eventually captured by Canadians on 6 September 1944.
Shortly afterwards the Germans began their V2 campaign but all launches were from mobile units around the Hague rather than from fixed bases. Around 1,300 V2s were eventually launched at the UK (mainly at London) and many more at Antwerp. The warhead of the V2 was similar to the V1 but the death and injury rate was around twice as high. Unlike the doodlebug, the V2 arrived with no warning at around four times the speed of sound. As well as the expensive single use delivery vehicle, the V2 needed around 3 tonnes of alcohol and 5 tonnes of liquid oxygen to deliver its one tonne payload. It was the most expensive weapon developed by the Germans and through slave labour caused the death of more of those who built it than it did in action.
The Eperlecques site is now a museum with displays and other exhibits including a relocated V1 on its launch ramp. Nothing however can upstage the immense structure itself – the largest bunker in Northern France.