A short history of the Fortress at Vijfhuizen and the Defence Line of Amsterdam

The Fortress at Vijfhuizen is part of the ‘Stelling van Amsterdam’ (the Defence Line of Amsterdam), a complex of fortresses, dikes, locks and other structures in a large circle around the capital. These fortifications were constructed from around 1880 till 1920 (figure 1). In case of a military threat, the territories outside the circle could be inundated, while more than forty fortresses protected strategic points where roads, rivers or dikes intersected the defence line. In times of trouble the inundation fields could be flooded by as little as 40 centimetres of water, too shallow to use boats, whilst obstacles such as canals became invisible forming a threat to horse-drawn carriages. This defence line by water would protect Amsterdam and make it invincible.

The Fortress at Vijfhuizen was constructed before 1900 and is one of the earliest fortresses in the defence line. Its role was described as: ‘To close and defend the access, which is formed by the Ringvaart canal and the dike around the Haarlemmermeer polder, the Spieringweg road and the dry stretch of land along the western border of the Haarlemmermeer polder’. The fortress at Vijfhuizen was built using unfortified concrete according to the Model A type (figure 2). It has a large main building with two wings connected to a smaller front building by a corridor called 'Poterne'. The main building consists of a series of interconnected quarters for soldiers or officers. Two gun posts with artillery were constructed to defend the flanks of the fort, in addition heavy artillery in two large gun turrets protected the front. In the Second World War, the Germans added a third gun turret.

 The fortress is situated on a small island surrounded by two canals, which is unusual (figure 3). This was intended as an extra barrier for approaching enemy armies, since this section of the surrounding Haarlemmermeer polder would remain dry when the polder was inundated. On the other side of the fortress, runs the Geniedijk embankment. This dike cuts right through the Haarlemmermeer polder. Under siege the southwestern part of the polder would be inundated while the north eastern part remained dry. At the bottom of this embankment a large steel hangar, 'Genieloods', was constructed in 1896. Its purpose was to store artillery, under the close watch of the fortress warden who lived next door in the guardian's house. Around 1910, a rail track was constructed. It ran parallel to the Geniedijk and was in use from 1912 to 1936; taking passengers from Haarlem to Hoofddorp and on to Aalsmeer.

The Defence Line of Amsterdam was an impressive feat of military engineering. However, it was all but ready when other innovations in warfare and artillery, particularly the invention of the airplane and heavier grenades, made it nearly obsolete. Hence, not long after the Second World War, most fortresses were abandoned and the Defence Line of Amsterdam was largely forgotten. The Fortress at Vijfhuizen lost its function as a military object in 1951. Roughly since the 1960's it was used for several decennia to store confiscated illegal fireworks.
In the 1980's the Defence Line of Amsterdam was rediscovered, first by a small group of enthusiasts, then later there was growing interest from policy makers and politicians. The Province of North Holland started initiatives to revive the appreciation for the Defence Line of Amsterdam and created the 'Stelling van Amsterdam' foundation for this purpose. In 1996 the entire military complex was added to the Unesco list of World Heritage. However, to find an actual new role for these forts, which is essential for their preservation, proved complicated. Nonetheless, it is not impossible, as the Art Fortress demonstrates. Hopefully, this initiative forms a source of inspiration to re-use and preserve other forts in the impressive Defence Line of Amsterdam.