The Netherlands and water have always been intricately and permanently linked. Because large parts of the country are below sea level, its inhabitants have been fighting floodwaters for as long as anyone can remember and this has resulted in an ingenious hydrological system. The pinnacle of this battle against water is a military defence system that's not only the largest and most expensive infrastructure project ever executed in The Netherlands, but also anywhere else in the world.
However, water isn't the only enemy of the state. In difficult times, when under threat of war and facing an approaching army of foreign invaders, water became a welcome ally and the nation's best line of defence. The wet Dutch countryside, with its numerous ditches and channels, was particularly unusual fighting terrain for most enemies. There was little room for large-scale battlefields and an abundance of mud and water made for difficult obstacles. In times of danger the amount of water was increased by intentional inundation, or the submerging of land. In this manner water became one of the most important elements of Dutch defence. Holland’s biggest secret weapon, the Dutch Waterline, was the result of this clever strategy. On paper, anyway. Many obstacles had to be broken down, before this defence line was indeed put into place.

Defence
The waterline concept dates back to 1589. In this pivotal year the states of Utrecht and Holland ordered Prince Maurits to investigate the most efficient manner of defence for the young Republic of the Seven United Netherlands. A waterline making full use of geographical circumstances seemed an ideal solution. Where the higher parts of the Netherlands border the low-lying polders it's relatively easy to inundate the land by use of locks or breaking through dikes. These water barriers were 3 - 5km wide and only 30 - 60cm deep or about knee-high. The inundated fields were wide enough so the enemy couldn’t shoot across them and shallow enough to make navigation with boats impossible. And to make things worse, the ditches and trenches were invisible in the muddy water, which made wading across very treacherous. However, the construction of the 1672 Waterline was ‘quick and easy’ and not very well prepared. Many dikes had to be broken through with unintentional consequences. Too much land was inundated wreaking havoc on farm production and the economy in general. To prevent this from happening again the system had to be improved. Military and civil engineers worked together to create a perfectly manageable system. Remarkably, the whole project was directed at the ‘enemy from the south and the east’ (i.e. Germany).
The largest cities in the west were protected with a defensive line 85km long which started east of Amsterdam at Muiden and stretched far south of Utrecht as Biesbosch/Werkendam). In 1815 King William I decreed the actual construction of the new Waterline for the brand new Kingdom of the Netherlands. But it would take another 70 years before the entire inundation system and the construction of the crucial locks and forts was completed in 1885. Converted into today’s money, more than 50 billion euros were invested in the New Dutch Waterline. This makes the Waterline the largest and most expensive civil engineering project ever executed in The Netherlands.

A quiet end
In contrast to the 1672 Old Waterline, the new one was never in a position to prove its defensive value, as it was never attacked and was never fully inundated. After World War II the Waterline no longer played a prominent role and was quietly forgotten. Yet many parts of this remarkable defence system were not declassified until 1951, the official date of the Line's abolition. After more than 300 years of loyal service, the Waterline was finally retired from active service.
The remnants of the New Dutch Waterline are now seemingly scattered at random throughout the land. Some parts don’t stand out and are more or less invisible. But the position of the different parts of the Line is all but coincidental and the actual Waterline is only visible when it's actually put into service. Nowadays the forts and concrete bunkers are the most visible and tangible remnants of the former military system, but for years the public was denied admission, the fortifications were excluded from civil maps and it was unlawful to photograph them. Since 2000 the government and local businesses have worked together to develop the Waterline and its 50 forts and more than 900 hydraulic and military constructions as potential tourist attractions and centres of recreation. Each fort was adapted to the demands of the specific landscape and is therefore a unique structure. A number of forts have already been given new functions. Some serve as wine tasting venues, botanical gardens, scouting centres, conference rooms and even training centres for police dogs. Today there are plenty of opportunities to visit the forts. You can follow the route on foot, by bike or by car. Some forts are still owned by the military and others have been converted into accommodation, while some have been abandoned to the elements. Still other fortifications are only accessible in September, during Forts Month, but many can be visited throughout the year. The website www.nieuwehollandsewaterlinie.nl offers a wealth of information. From now on the well-kept post-military landscape occupies a place of prominence not only as a unique feature on the map of Holland, but also as a shared secret to be enjoyed by us all.