From castle to Dutch Waterline
For centuries, laying siege was the one and only way to conduct war. In the Middle Ages, each city had its own defences – sometimes in stone, but mainly as earthen structures with stone entryways. Canals surrounding the cities also offered protection. Castles were built at strategic locations, for example along a river. Two such castles within the New Dutch Waterline still exist: Muiderslot and Loevestein Castle.
The invention of artillery in the 15th century forced the creation of a new type of defence infrastructure. In addition, the Eighty Years' War made defence works highly necessary. Alternative types of fortifications gave rise to the New Dutch system in which defence lines replaced freestanding fortifications.
From old to New Dutch Waterline
The Netherlands first began using water to protect itself during the Eighty Years' War by breaching dikes to flood polders. In 1672, the first waterline was hastily erected against the invading French forces. Known as the Old Dutch Waterline, it ran from Muiden to Woerden, through Schoonhoven, towards Gorinchem, and westward from the city of Utrecht. After 1815, Utrecht was included within this line of defence as part of the New Dutch Waterline.
In order to obstruct the enemy, a waterline could not be passable or navigable. But variations in the landscape, for example rivers and dikes, left some areas dry, and thus passable by the enemy. These access points were defended by forts, batteries and bunkers, where troops were housed and artillery was positioned.
Forts needed an open line of fire, which was why the building of any obstacles within one kilometre around the fort was regulated as part of the Prohibited Areas Act. The Waterline formed a connected military landscape: a system of geographical and water management agreements surrounding landscape elements such as fortifications and water works.