The New Dutch Water Line (Nieuwe Hollandse Waterlinie) was an 85-kilometer long military line of defence that protected the economically important western part of The Netherlands. It was an improvement over the Old Dutch Water Line and protected also the important city of Utrecht. The line used water as primary weapon. A shallow layer of water (about 40 to 60 centimetres) was deep enough to make the land difficult to pass by an enemy army, but the water level was not high enough to navigate by ship. A complex system of flood canals, sluices and dikes was used to flood the land in case of an emergency.
Access points were areas of higher ground that could not be flooded. These weak points were strengthened with forts, batteries and roadblocks. Troops and artillery were concentrated on the forts. The buildings were “bombproof” and protected the defenders against enemy fire. The line was mobilized three times but never saw any action. The only battle it had to fight was a continuous battle against obsolescence. Technological improvements in ammunition and artillery made the construction of the forts no longer “bombproof”. The forts had to be modernized continuously.
At the end of the nineteenth century the army changed strategy. Artillery and troops were no longer concentrated on the vulnerable forts, but were placed in the field. Different types of concrete group shelters were built to protect the army against enemy fire.
In 1940, the high command decided, just before the German invasion, to concentrate the main defense on the more eastern Grebbe Line. The New Dutch Water acted as a second line of defence, but because of the rapid capitulation of the Dutch army it didn’t see any action. World War II proved that waterlines were no longer useful because of the use of airplanes. The New Dutch Water was lifted in 1951 as military line of defense.