Defending Amsterdam with water

The Defence Line of Amsterdam

To protect themselves from attack over the years, humans have shown an impressive level of inventiveness. We’ve used mountains, moats, walls, spikes, rocks… and more.

But only the Dutch learned to control the movement of water and use that for their fortifications.

In the lead-up to the First World War, nobody knew they were in the lead-up to the First World War. That’s kind of the way these things go.

But, nonetheless, the Dutch were working hard to protect their capital Amsterdam from any possible threat within Europe.

Without the benefits of mountains to build castles on or grand rivers to provide a natural barrier, they looked to what they had – which turned out to essentially be a lot of swampland.

For centuries the Dutch had used a clever system of dykes, canals and hydraulics to clear the swampland and create space that could be used for communities and farming.

The best example of this, the Beemster Polder, is an area of more than 70 km² that was essentially a shallow lake before being reclaimed through mechanics and ingenuity.

So when it came to fortifications, the Dutch shifted their gears into reverse and thought about how this could be used to their advantage. They realised that if they undid all their hard work and filled up these spaces with water again, they could effectively create an enormous moat around Amsterdam.

To achieve this, the Dutch built what is now called ‘The Defence Line of Amsterdam’ or ‘Stelling van Amsterdam’.

It was a rough circle stretching for 135 kilometres all around the capital city and the important settlements nearby, with a radius of about 15 kilometres.

Along the line were built 45 armed forts, which were to be the key to operating the barrier if war came too close for comfort.

In basic terms, the defence program would use hydraulics to open gates and pump water from canals into low-lying plains, covering roads and land that an enemy would have to use to get to Amsterdam.

Some of the water would be too shallow to use boats, while the deeper areas were protected by the forts, which were armed with cannons and other artillery.

Pampus Island, The Netherlands

The island of Pampus, not too far from Amsterdam in a region called Muiden, is one of these forts.

It’s an artificial island that took eight years and 45,000 cubic metres of sand to build. It sits in the middle of the water, hundreds of metres from land, like a rocky omen of war in an otherwise peaceful bay.

The huge guns that once sat on top of the fort had a range of about eight kilometres. An enormous 280kg shell could be fired every six minutes and the belief was that would be enough to stop any attackers trying to come by boat in this direction.

Today the fort island has been turned into a museum and educational centre. The structure remains the same and you can crawl through hidden tunnels or walk through the maze of rooms beneath the high domed roofs.

It’s surprisingly big once you get inside and it takes quite a long time to see everything. Some of the rooms have been left as they were but many of them have been updated with clever video displays, holograms and lighting effects.

School children sometimes stay here for several days for camps and these elements are needed for amusement.

As it turned out, the Defence Line of Amsterdam was never needed. The Netherlands managed to stay relatively neutral in World War I and were not directly attacked.

By World War II, planes had become common and a barrier of water was not enough to stop the bombardment from the Germans. Part of the flooding was activated when the Nazis invaded in May 1940 but there was no fighting and it did little to stop the advance from other directions.

The combination of human inventiveness and the harnessing of nature does make this fortification very special. Many of the forts are still standing and open to the public, so it’s easy to get a sense of how it was designed.

But we will never know how effective it would have been because almost as soon as it was completed, it became obsolete.