Dutch Mounted Field Artillery with a 7cm Field Cannon on their way during an inundation during the mobilization, November 1939.

 Dutch Mounted Field Artillery with a 7cm Field Cannon on their way during an inundation during the mobilization, November 1939.

A bit of History

The Dutch Water Line was a series of water-based defences conceived in the early 17th century. 

Combined with natural bodies of water, the Water Line could be used to transform the ‘Holland’ Provinces almost into an island.

Early in the Eighty Years' War of Independence against Spain (1568-1648), the Dutch realized that flooding low-lying areas formed an excellent defence against enemy troops. 

Sluices were constructed in dikes and forts and fortified towns were created at strategic points along the line with guns covering especially the dikes that traversed the water line.

The water level in the flooded areas was carefully maintained at a level deep enough to make an advance on foot precarious and shallow enough to rule out effective use of boats (other than the flat bottomed gun barges used by the Dutch defenders). 

In wintertime the water level could be manipulated to weaken ice covering, while the ice itself could be used when broken up to form further obstacles that would expose advancing troops to fire from the defenders for longer.

The Dutch Water Line proved its value less than forty years after its construction during the Franco-Dutch War (1672), when it stopped the armies of Louis XIV from conquering Holland, although the freezing over of the line came close to rendering it useless. 

It was further extended and modernised in the 19th century, with forts containing round gun towers reminiscent of Martello towers. 

The line was mobilised but never attacked during the Franco-Prussian war in 1870 and World War I.

At the advent of World War II, most of the earth and brick fortifications in the Water Line were too vulnerable to modern artillery and bombs to withstand a protracted siege. 

To remedy this a large number of pillboxes were added. However, the Dutch had decided to use a more eastern main defence line, the Grebbe Line, and reserved a secondary role for the Water Line.

When the Grebbe Line was broken on May 13, the field army was withdrawn to the Water Line. However, modern tactics could circumvent fixed defense lines, as happened during the French Maginot Line. 

While the Dutch army was fighting a fixed battle at the Grebbe Line, German airborne troops captured the southern approaches into the heart of "Fortress Holland" by surprise, the key points being the bridges at Moerdijk, Dordrecht and Rotterdam.

When resistance did not cease, the Germans forced the Dutch into surrender by aerial bombing of Rotterdam and threatening the same for Utrecht and Amsterdam.

From its conception in 1815, until the last modernisation in 1940, the equivalent of around 50 billion euro was spent on the New Dutch Water Line.

Today many of the forts are still more or less intact. There is renewed interest in the waterline for its natural beauty.

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