Defence lines in the Netherlands
By the end of the 16th century, the Seven United Provinces (of the Netherlands) revolted against Philip II of Spain and formed their own Republic. From that moment on, the Dutch continually worked on erecting a defence structure. Besides defence at sea, attention was paid to land-based defence, where the natural landscape played an important role. The Dutch made use of the extended river landscape and swampy regions. Fortified cities, and sometimes forts, were placed in locations where nature presented no obstacles. This resulted in a connected network of fortifications (frontier cities) and defence lines.
West Brabant Waterline
In 1698, the Republic's fortifications expert, Menno van Coehoorn, made plans to improve the fortifications of Bergen op Zoom, Steenbergen as well as other forts. A defence line called the West Brabant Waterline (West Brabantse Waterlinie) was constructed between the cities Bergen op Zoom and Grave.
IJssel Line
Between the more than 20 towns along the border, there were a number of natural and artificial defence lines. The Veen Line ran along the eastern boarder between Bourtange and Coevorden, the IJssel Line (IJssellinie) between Zwolle and Arnhem. The Zuider Waterline ran along the lower reaches of the Maas River. Finally, there was a line of fortifications east of the province of Zeeland which connected to the Spanish–Flemish Line in Zeeuws-Vlaanderen. Somewhat apart ran a defence line near Maastricht.
Grebbe Line
If the enemy broke through the first line, two extra defence lines (the Dutch Waterline and the Grebbe Line), which ran between the Zuiderzee and the Delta region, could be put to use.
Stelling van Amsterdam
Some new lines were still being built by the end of the 19th century and during the 20th century, namely, the Stelling van Amsterdam, the Peel-Raamstelling and the renovated IJssel Line. Although the Dutch Waterline had functioned well for centuries as the main defence line of the Republic, and later the Kingdom of the Netherlands, at this point it had outlived its usefulness and so no longer played an important role in national defence.
The Old Dutch Waterline
The first successful strategic flooding took place in 1589 when Prince Maurits broke through the siege of Leiden by flooding the land around the city. In 1629, the first provisional waterline was built to defend the provinces of Holland and Utrecht. But because of dissent between the cities of Utrecht and Amsterdam, it fell into disrepair.
The threats from France, England and some German states lead to an invasion in that disastrous year of 1672. The Republic of the Seven United Provinces of the Netherlands had a weak defence system. As the French reached Utrecht, a waterline was still quickly being improvised. This Old Dutch Waterline ran from Gorinchem, over the Goejanverwelle sluice and Woerden, towards Muiden. A wide inundation strip ran between these locations, which could be flooded in sections with water from rivers, polder drainage pools and the Zuiderzee. Floods were broken up here and there by dikes with higher-lying areas that were also referred to as access points. The Wiericker bulwark was an important part of the old line and is one of the few elements that remain in existence today.
Flooding still cost lots of time in 1672 and sometimes not enough water could be let through the sluices. Quays had to be cut through, which lead to opposition by farmers and cities that saw agricultural lands lost. After much hardship, the flooding was completed before the French assault, and by 1676, the peace treaty was signed. The Republic decided to expand the successful waterline into a permanent defence line: the New Dutch