The Wierickerschans Fort is a part of the Old Dutch Waterline or "Oude Hollandse Waterlinie". This was a defence system that allowed large parts of the country (Holland) to be flooded (inundated). Thus protecting the main towns and city in the West against invading forces from the East. It was in use right up to the 19th century. The Fort was built on the site where in 1672 Stadtholder Willem III (William of Orange, who later became King of England) had his headquarters during the war against the French.