The Stelling van Amsterdam (pronounced[ˈstɛlɪŋvɑnˌɑmstərˈdɑm]; "Defence Line of Amsterdam") is a 135-kilometre (84 mi) fortification line around Amsterdam, which would function as a national redoubt. It comprises 45 forts, as well as dams, dikes, locks, pumping stations, batteries and casemates.[1] The forts are 10–15 kilometres (6.2–9.3 mi) from the centre and lowlands, which can easily be inundated in time of war.[2] The inundation was designed to give a depth of about 30 centimetres (12 in), too little for boats to cross. Any buildings within 1 kilometre (0.62 mi) of the line had to be made of wood so that they could be burnt and the obstruction removed.
The Stelling van Amsterdam was constructed between 1880 and 1920. The Stelling was mobilised and partially inundated during the first World War, but the Netherlands remained neutral and was not invaded. In 1922, the Stelling became part of the Fortress Holland [nl]. The north side of the Stelling was inundated when Germany invaded in 1940 at the start of the second World War, but the Netherlands capitulated before the Germans reached the Stelling.
A combination of inundation and posts to protect Amsterdam date back as far as 1629, when these were prepared against a planned but later cancelled attack from the south by the Spanish general Ernesto Montecuccoli during the Eighty Years' War. Another water defence line was prepared in the south in 1672, the Rampjaar, but the invaders failed to get past the Old Dutch Waterline. In June 1787, 27 posts were created by the Patriots and on 18 September 1787, the surrounding polders were inundated. These posts held back the Prussian invasion, but the Prussians managed to get access through the Haarlemmermeer and successfully attacked the posts from behind.[3]
The Stelling van Amsterdam was primarily a defensive water line (Dutch: waterlinie). In the event of an enemy attack, large tracts of land around Amsterdam would be inundated with water, preventing the enemy from advancing. Amsterdam would function as a national redoubt or reduit, as the last stronghold of the Netherlands. Forts were built in which roads, railways or dikes crossed through the water line. At such locations, there would be no water to stop the enemy and so the forts were intended to shell the enemy.
Construction
The law for the construction of the Stelling van Amsterdam was passed in 1874, a few years after the Unification of Germany, which placed a powerful new great power on the eastern border of the Netherlands. During the planning prior to its construction, the design was already obviously outdated by modern technical advances. The invention of the high-explosive shell and the percussion fuze, which allowed ordnance to explode on impact and dislodge brick fortifications easily, necessitated a change from masonry to concrete forts. The Dutch did not have the required experience yet using and building with concrete and so extensive tests had to be performed. Concrete structures were shelled with the heaviest artillery available at that time. Further delays resulted from the fact that the sand foundations had to settle for several years before the forts could be built on them. Only in 1897 could the actual construction finally begin.
Service
The Stelling van Amsterdam has never seen combat service and the use of aircraft rendered it obsolete after World War I. It was, however, maintained and kept in service until it was decommissioned in 1963.
The dike through the Haarlemmermeer, which made it possible to inundate the southern portion of the polder while the northern portion could continue to produce food for Amsterdam, is now cut by the A4 motorway. The motorway also goes under the Ringvaart at Roelofarendsveen, which makes the inundation of the Haarlemmermeer Polder and thus the future use of the Stelling no longer possible.
