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The Hollandic Water Line (Dutch: Hollandse Waterlinie), is a three-part defence work between the IJsselmeer and the Biesbosch, as well as around the capital of Amsterdam in the Netherlands. The works consist of many forts, batteries and other defence works, amongst which the most notable are the many dedicated inundation plains.
The Hollandic Water Line, or rather Water Lines, are three systems of floodable polders that functioned as a defence work to the County of Holland and later Amstelland, the economic capital of the Dutch Republic and the later Netherlands. The construction of the three systems is divided in three parts, namely constructions between 1672 and 1815, between 1815 and 1871, and the works constructed around the capital city of Amsterdam. These are respectively the Oude Hollandse Waterlinie (Old Hollandic Water Line), Nieuwe Hollandse Waterlinie (New Hollandic Water Line) and the Stelling van Amsterdam (Amsterdam Defence Line). The latter of which is a registered UNESCO World Heritage Site. The defence works were all created to defend the country's economic centre should a war break out, and the Netherlands be invaded, which was the reason as to why the defence works were started in the first place.
1672 is known as the Rampjaar (Year of Disasters) in Dutch history, and is seen as the year that the Dutch Golden Age ended. Inundation systems existed at the start of the Rampjaar, which those of Alkmaar (1573) and Leiden (1574) predated the Waterlinies by about a century. A nation-wide defence work, however, did not exist. During the Rampjaar, the Dutch Republic was attacked by France, England and the Bishoprics of Cologne and Münster, in which the French did most of the fighting. After quickly overrunning and raiding the eastern Netherlands, the French besieged Utrecht for several years with about 30.000 men, waiting patiently for the Dutch to accept their peace treaty, which meant that the Dutch transferred the Southern Netherlands to France, gave England Walcheren, and ceded some of the Eastern Netherlands to Cologne and Münster. The Dutch, meanwhile, outed their frustration about the war on Grand Pensionary Johan de Witt, who, along with his brother Cornelis was brutally lynched in The Hague during the Rampjaar. He was blamed as the Dutch army, which was quickly overrun and beaten, had seen many budget cuts, with De Witt and Grand Pensionaries before him favoring trade over war. As soon as frustration was outed, however, the Dutch set to quickly create a defence work that the French could not cross. They decided to turn to their worst enemy: the sea.
The Netherlands (lit. Low Countries) had been reclaiming land from their seas and rivers for a while already, and put one and two together, to come up with the idea of puncturing some of the dikes that held back the water, and in that way flooding the area between Muiden and Gorinchem. The French did not want to cross the Waterlinie, but did so during the winter, but had to retreat as soon as the ice started melting again, as to not get stranded in enemy territory without supplies. The peace treaty, for that reason, was easy on the Dutch. The works were later expanded further eastward towards, but never reaching Utrecht, until the Napoleonic Era. The works created after that, during the existence of the Kingdom of the Netherlands, founded in 1815, are counted as part of the Nieuwe Hollandse Waterlinie.
The Nieuwe Hollandse Waterlinie aimed to defend more of the Netherlands, with the biggest improvement being that Utrecht was defended as well. The line, spanning from Pampus in the IJmeer to the Biesbosch, a total of 85 kilometres (53 mi), with an average width between three and five kilometres, counts a total of 46 forts, connecting the fortified cities of Muiden, Weesp, Naarden, Gorinchem and Woudrichem. The extensively planned works started in 1815, quickly after the start of the Kingdom of the Netherlands, was started after Cornelis Krayenhof, the then director of Dutch fortifications, lobbied extensively for a shift of the existing Oude Hollandse Waterlinie. Even Napoleon had been impressed with the existing defence works after he annexed the country in 1811, and he himself wanted to improve it and extend it to surround Amsterdam, as the Stelling van Amsterdam would. He, however, never managed to even start that project, as he would be defeated four years later at Waterloo. The new line, finished in 1870, would never be truly finished, as the Industrial Revolution sparked many new innovations quickly succeeding each other, meaning that the line had to be constantly updated until the mobilisation of 1939. The forts definitely were the most notable and visible element of the line, but the many small locks and barriers may arguably have been the more important works. One barrier had to be sabotaged and the entire water level of the inundation plains could be too low.
The Stelling van Amsterdam was the third defence line located at 15 to 20 kilometres from the capital city of Amsterdam. The line is 135 kilometres (84 mi) long, and counts 45 forts. Constructed between 1880 and 1920, the Stelling has been UNESCO World Heritage since 1996. Unlike the Waterlinies, the Stelling's forts are made out of concrete (excluding a few that were made early into the project). Compared to the forts on the Waterlinies, the forts on the Stelling were very much modern, being built into the ground, rather than standing tall above the surrounding vegetation.