Fort des Dunes The Fort des Dunes , also known as Fort Leffrinckoucke and sometime Fort de l ' Est , is located in the commune of Leffrinckoucke , France , about east of Dunkerque . Built from 1878 to 1880 , it is part of the Séré de Rivières system of fortifications that France built following the defeat of the Franco - Prussian War . Although it played no part in World War I , it had a significant role in both the beginning and end of World War II . It has been preserved and is interpreted by a local preservation association for the public . Description . The Fort des Dunes was built as the westernmost frontier fort in the Séré de Rivières system , in the coastal sand dunes within a few hundred metres of the English Channel . The chosen site was both served by and a place of protection for the coastal railway and canal . It occupies a sandy hill high , and is itself protected by as many as of sand cover . The rectangular fort is surrounded by a dry moat defended by caponier s that provide a protected firing position to sweep the length of the ditch with gunfire . The main fort is accessed by a drawbridge over the ditch . The Fort des Dunes was armed with a variety of artillery over its history , initially mounted on the fort ' s surface . The fort ' s barracks and service areas are recessed into the surface and covered with soil and turf . The walls are built of brick and stone masonry . It was initially armed with about 25 artillery pieces , served by 451 men . The Fort des Dunes was a component of a larger system of coastal batteries and outlying positions defending the greater Dunkerque area . These fortifications were modified as artillery technology developed , making fixed open - air gun emplacements untenable . During World War I the fort ' s primary armament was two or three 90mm guns on the ramparts . Several 120mm anti - aircraft guns were positioned in the area surrounding the fort . History . The Fort des Dunes did not see action during the First World War , since it was well behind the lines . It was garrisoned largely by reservists . The fort ' s primary function during this time was as a munitions depot . Operation Dynamo . During the Battle of France in 1940 , large numbers of French and British troops arrived in the Dunkerque area , separated from their units . The Camp des Dunes was established at the fort to process French soldiers and to assign them duties . General Georges Blanchard , whose First French Army had effectively ceased to exist , arrived at the fort on 30 May . The fort became the headquarters of the French 12th Motorized Infantry Division on 1 June . On 2 June the fort was attacked by aircraft . Two bombs exploded in the courtyard of the fort . Among the dead was the 12th Motorized Infantry ' s General Janssen . Another bombing raid on 3 June hit the fort with six bombs , heavily damaging the fort and killing six more officers , with a total of between 150 and 200 killed at the fort in both raids . The repeated attacks and heavy damage led the 12th Division to leave the fort . Following the last evacuations from the beaches and port of Dunkerque on 4 June , German forces took possession of the fort . The Germans made repairs to the fort and organized reburials of soldiers who had been interred where they had fallen or who had been entombed by debris , mostly carried out by local citizens and prisoners of war . The fort became a component of the German Atlantic Wall fortifications , primarily as an annex to the Zuydcoote battery . Apart from functioing as a rations depot , the fort supported an anti - aircraft battery with a radar installation . A small blockhouse was built by the Todt Organization on the west side , with another bunker covering the approach road . These were reinforced in 1944 with temporary revetments and a heavy machine gun position . German troops left significant murals and decorations in the magazines and barracks . 1944 . On 4 September 1944 an attempt to kill a German soldier was made by the French Resistance in Rosendäel . The house that the assailant fled to was surrounded and the occupants arrested . All eight were arrested and held at the Fort des Dunes , except for Daniel Decroos , who had been killed while trying to escape . Another detainee had been wounded by an exploding grenade . On 6 September six detainees were executed by firing squad in the north ditch and the wounded detainee was euthanized . The seven were buried next to the ramparts . The wall where the prisoners had been shot was destroyed and collapsed on the graves . Following the Liberation the execution was investigated and the graves discovered . The remains were exhumed and reinterred . German forces held the Dunkirk Pocket through the Siege of Dunkirk to the end of the war , when they surrendered . 10 , 000 Germans were taken prisoner on 9 May 1945 . 3700 Germans were kept in the Dunkerque area , with many at the Fort des Dunes . The prisoners were engaged in cleanup and mine removal . After the departure of the prisoners the fort was transferred to the customs service , who used it as a storage centre for seized goods . A customs officer and his family lived at the fort . The fort went back to the army in 1955 , which began excavations to recover the remains of those killed in 1940 . A ceremony of re - interment was held in August 1955 , attended by the widow of General Janssen . The fort was then abandoned for twenty years . In 1978 a local organization was formed to preserve the fort as a center for military reserve functions . By 1990 the fort had been made habitable . Present . The Fort des Dunes is maintained and interpreted by the Association Fort des Dunes . It is usually open to the public on summer weekends . It was transferred to the commune of Leffrinckoucke in 1998 . The fort still shows the scars of the 1940 bombardment , with the entry tunnel largely exposed .