The Blockhaus d'Éperlecques, La Coupole and the Fortress of Mimoyecques were military complexes built in north-eastern France by Nazi Germany between March 1943 – July 1944. They were constructed by a large workforce of German specialists, civilian forced labourers and prisoners of war used as slave labour, and were intended to serve as launch sites for the Nazis' secret weapons, the V-2 rocket (pictured at La Coupole) and the V-3 supergun. The Blockhaus and La Coupole, located near Saint-Omer, were designed to launch dozens of V-2 rockets daily against London and other targets in England. The Fortress of Mimoyecques, near Boulogne-sur-Mer, would have housed the V-3 supergun, designed to rain 600 projectiles an hour on London. All three facilities were put out of action by intensive Allied bombing carried out in Operation Crossbow between August 1943 – August 1944 and were never used for their intended purposes. They were captured by Allied forces in September 1944 and partly demolished on Winston Churchill's orders to ensure that they could not be used to threaten the United Kingdom again. They were abandoned after the war before being opened to the public in the 1980s and 1990s as museums.
Full articles: Blockhaus d'Éperlecques – La Coupole – Fortress of Mimoyecques