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, French forced labourers and Soviet 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 southern England. The Fortress of Mimoyecques, near Boulogne-sur-Mer, would have housed the V-3 supergun, designed to rain 600 projectiles on London every hour. All three facilities were put out of action by intensive Allied bombing carried out in Operation Crossbow between August 1943 and August 1944 and were never used for their intended purposes. The sites were captured by Allied forces in September 1944 and partly demolished on the orders of Winston Churchill to ensure that they could not be used to threaten the United Kingdom again. They were abandoned for a period after the war before being opened to the public in the 1980s and 1990s as museums.