The Stelling van Amsterdam (pronounced [ˈstɛlɪŋ vɑn ˌɑmstərˈdɑm]; "Defence Line of Amsterdam") is a 135-kilometer (84-mile) line of forts and barriers surrounding Amsterdam. It was built to act as a national stronghold. The system includes 45 forts, along with dams, dikes, locks, pumping stations, batteries, and casemates. The forts are located 10 to 15 kilometers (6.2 to 9.3 miles) from the city center and lowland areas, which could be flooded during wartime. Flooding was planned to create water about 30 centimeters (12 inches) deep, too shallow for boats to cross. Any buildings within 1 kilometer (0.62 miles) of the line had to be made of wood so they could be burned and removed if needed.

The Stelling van Amsterdam was built between 1880 and 1920. During World War I, the system was activated and partially flooded, but the Netherlands stayed neutral and was not attacked. In 1922, the Stelling became part of the Fortress Holland. During World War II, the northern part of the Stelling was flooded when Germany invaded in 1940. However, the Netherlands surrendered before German forces reached the line.

The Stelling van Amsterdam is part of the UNESCO World Heritage Site known as the Dutch Water Defence Lines.

Background

In 1629, a combination of flooding and defensive posts was created to protect Amsterdam. These measures were prepared to defend against a planned attack by Spanish general Ernesto Montecuccoli from the south during the Eighty Years' War, though the attack was later cancelled. Another water defense line, known as the Rampjaar, was built in the south in 1672. However, invaders could not advance past the Old Dutch Waterline. In June 1787, 27 posts were established by the Patriots. On September 18, 1787, the surrounding polders were flooded. These posts helped stop the Prussian invasion, but the Prussians eventually accessed the area through the Haarlemmermeer and attacked the posts from behind.

In 1799, when the English invaded Holland, a water defense line was created north of Amsterdam, led by engineer Cornelis Krayenhoff. In 1800, Krayenhoff also designed the Line of Beverwijk to the west of Amsterdam, fearing another English invasion. When the threat decreased the following year, the posts were neglected. In 1805, Krayenhoff was asked to build a new defense line because King Louis Bonaparte worried about the Netherlands being taken over by the First French Empire. These posts, known as the Posts of Krayenhoff, were constructed between 1809 and 1810, located 8-12 kilometers from the city. The peaceful incorporation of the Netherlands into France in 1810 meant the posts were not used. Plans to improve the posts were made, but they were not completed due to the Netherlands being liberated in 1813. In later years, new forts were added to the Posts of Krayenhoff in the Haarlemmermeer polders: Fort near Heemstede, Fort along Schiphol, Fort along the Liede, and Fort along the Nieuwe Meer.

Function

The Stelling van Amsterdam was mainly a defensive water line (Dutch: waterlinie). If an enemy attacked, large areas of land near Amsterdam would be flooded with water, stopping the enemy from moving forward. Amsterdam would act as a national stronghold, the last safe place in the Netherlands. Forts were built at places where roads, railways, or dikes crossed the water line. At these points, there was no water to block the enemy, so the forts were built to attack the enemy with cannons.

Construction

The law to build the Stelling van Amsterdam was passed in 1874, a few years after Germany united, creating a strong new neighbor near the Netherlands. Before building, the plan was already old because of new technology. High-explosive shells and fuses that made explosives explode on impact and damage brick forts led to using concrete instead of brick. The Dutch didn't know how to use concrete well, so they did many tests. Heavy artillery was used to test concrete structures. Delays happened because the sand foundations needed time to firm up before building. Construction finally started in 1897.

Service

The Stelling van Amsterdam was never used in battle, and the invention of airplanes made it unnecessary after World War I. It remained in use until it was taken out of service in 1963.

A dike through the Haarlemmermeer allowed water to flood the southern part of the polder while the northern part could still grow food for Amsterdam. Today, the A4 motorway crosses this dike, and it also passes under the Ringvaart near Roelofarendsveen. These changes mean that flooding the Haarlemmermeer Polder, and therefore using the Stelling in the future, is no longer possible.

In 1996, the entire Stelling was named a UNESCO World Heritage Site. In 2021, the site was expanded to include the New Dutch Waterline, forming the Dutch Water Defence Lines.

Fortifications

• Floodgate at South Beemsterringdijk (Dutch: Inundatiesluis zuidelijke Beemsterringdijk)

• Amsterdam Cavalry Barracks
• Oranje-Nassau Barracks

• Ammunition Complex De 1800 Roeden (Dutch: De 1800 Roeden)
• Old Mill (Dutch: Ouderkerk aan de Amstel)
• Stone Silo (Dutch: Steensilo)