Fort Breendonk owes its existence to the strategic importance of Antwerp in the 19th century. Antwerp was developed into a "national redoubt", a kind of fortress, in which the government and other prominent people were able to hide from an enemy attack. For this purpose, a belt of forts was established around the city. At the beginning of the 20th century the construction of eleven new forts started, including Breendonk. In 1909, the construction of that fort began. Around the concrete buildings, a wide canal was created and the earth that came out of the canal, covered the buildings. At the entrance, a partly wooden drawbridge was made over the canal. In 1913, the first American soldiers moved into the fort. A year later, the Germans invaded Belgium for the first time. They did not immediately attack the redoubt, but guarded it with limited troops, while the main troops headed for France. Only when the offensive faltered did they focus on Antwerp. Just like other forts, Breendonk was not able to withstand the German shelling. On October 8th, a day after King Albert I had left the national redoubt, Breendonk surrendered. After the First World War, the fort did not play a significant role. It was only sporadically used during the interbellum.
That situation changed in May 1940. Despite the Belgian neutrality, German troops invaded Belgium for the second time in thirty years. Fort Breendonk was declared as general headquarters for the Belgian army. King Leopold III and his general staff installed themselves in the fort. At night, he retreated into the nearby Ch‚teau Melis. Initially, the atmosphere in the fort was optimistic but that changed very soon. The German armies seemed unstoppable and forced breakthrough after breakthrough. For that reason the general headquarters moved to Saint-Denis-Westrem on May 17 th. By then the fort was already in the frontline.
On May 28th, 1940, Belgium was defeated and Leopold III had no other option than to sign the surrender. For the Belgians, the war was over; even permanently in the eyes of many. Belgium was militarily governed by General Alexander von Falkenhausen. After the military, the Geheime Feldpolizei (GFP), the Sicherheitspolizei and the Sicherheitsdienst (Sipo-SD), with the Gestapo, settled in Belgium. The latter group turned Breendonk into the notorious Auffanglager.