Zonsondergang bij de Geniedijk, a photo by M-MZ on Flickr.
The Dutch Water Line was a series of water based defenses conceived by Maurice of Nassau in the early 17th century. Fortifying and combining natural bodies of water, it could be used to transform the Dutch Republic almost into a fortified island. 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 to 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).
This is fascinating.
Naarden, NL – not to be confused with Coevorden, NL
Instead of merely using ramped earth, the Dutch used shallow ponds full of water to repel invaders. Only an early frost permitted Napoleon to breach the defense. In addition to the shallow ponds (30cm / 12″ deep) the Dutch also fortified strategic locations starting with Renaissance fortifications – much like Coevorden, NL, then Martello towers then combined fortifications which ultimately became obsolete as war-fighting became mobile and airborne.
Today, most of the water line is still intact with the Stelling van Amsterdam (below, simplified image) declared an UNESCO World Heritage Site (you know how I love those Heritage Sites). I would love to visit these installations and undertake a long study of them.
More information: