How does an inundation work?
It’s quite simple: when the enemy approaches, you open up sluices to flood the polders. Instead of draining water away, you bring in the water from rivers and canals.
A layer of water of about 40 cm high in an area of some 3 to 10 kilometres wide should do the trick. The knee-high water makes it hard for the enemy to move: it’s too deep to walk through with heavy artillery and too shallow to cross by boat. The forts are used to defend the inundation sluices and access routes through the inundated area. It works great. Until the enemy brings along modern long-range artillery, that is.
Photos: Martin van Lokven