Early in the
Eighty Years' War of Independence against Spain, the Dutch realized that flooding low-lying areas formed an excellent defence against enemy troops. This was demonstrated, for example, during the
Siege of Leiden in 1574. In the latter half of the war, when the province of
Holland had been freed of Spanish troops, Maurice of Nassau planned to defend it with a line of flooded land protected by fortresses that ran from the
Zuiderzee (present
IJsselmeer) down to the river
Waal.
Old Dutch Waterline In 1629, Prince
Frederick Henry started the execution of the plan. Sluices were constructed in dikes and forts and fortified towns were created at strategic points along the line with guns covering 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). Under the water level additional obstacles like ditches and
trous de loup (and much later,
barbed wire and
land mines) were hidden. The trees lining the dikes that formed the only roads through the line could be turned into
abatis in time of war. 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. ; with a good view of the star-shaped layout of the earth
bastions, designed in the early gunpowder age to place outward guns to force an enemy to keep distance and thus to protect the town proper against shelling The Dutch Water Line proved its value less than forty years after its construction during the
Franco-Dutch War (or
Third Anglo-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. In 1794 and 1795, the revolutionary French armies overcame the obstacle posed by the Dutch Water Line only by the heavy frost that had frozen the flooded areas solid.
New Dutch Waterline After the final defeat of
Napoleon in 1815 at
the Battle of Waterloo, the
United Kingdom of the Netherlands was formed. Soon after King
William I decided to modernise the Water Line. The Water Line was partly shifted east of
Utrecht. In the next 100 years the main Dutch defence line would be the new Water Line. 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. After World War II, the Dutch government redesigned the idea of a waterline to counter a possible
Soviet invasion. This third version of the Water Line was erected more to the east at the
IJssel (the
IJssel Line) and in
Gelderland. In case of an invasion, the water of the
Rhine and the
Waal were set to divert into the IJssel, flooding the river and bordering lands. The plan was never tested, and it was dismantled by the Dutch government in 1964.
Dimensions and units At present Today many of the forts are still more or less intact. There is renewed interest in the waterline for its natural beauty. Bike tours and hiking paths are organised with the line as a theme. Some of the forts are open for bikers/hikers to stay the night. Others have a variety of uses, for example
Utrecht University houses its
botanical garden in Fort Hoofddijk. Due to the unique nature of the line, the Dutch government considered whether to nominate the whole defensive line as a
UNESCO World Heritage Site, as they did with the
ring of fortresses around Amsterdam. On July 26, 2021, the line was added as a UNESCO World Heritage Site. A 25-year plan has been developed by the artist,
Agnes Denes. In 2010, one of the forts on the Line Bunker 599, was opened as a publicly accessible work of art that was created through a cooperation between
RAAAF and Atelier de Lyon. The bunker was sliced open, with a walkway placed through it forming an installation allowing a view to look into and through the bunker. == Constructions==