Dutch Water Line


Location: 52° 4'30.46"N    5°10'36.40"O


Vossegatsedijk 3-5
3981 HS  Bunnik

A large plain on the south-east side of Utrecht stayed dry. This plain is called "De Houtense Vlakte".

To cover this access through the Water Defense Line, a row of 4 Lunettes was made, between 1822 and 1828.

Because the range of the artillery did increase, defense works had to be made at a greater distance from Utrecht.

Also the defense of this large access through the Dutch Waterline was extremely important and two of the largest fortresses, ever built in the Netherlands were made here.

Fort Rijnauwen was the largest one and built between 1868 and 1871.
It covers 31,4 hectares and is unique because it is the only fortress of the Polygonal type.

Here you see a general arrangement drawing of the fortress.

It has a front Caponnière 2, which is a large Casemate sticking out of the front wall, containing gun rooms on both sides, that give flanking fire along the front walls, over the front moat 1.

At the small inlets in the moat, at either side of building 6 are flanking Casemates, covering the arrow shaped head of the Caponnière.

All no's 3 are also flanking Casemates covering the sides of the fortress.

No. 4 is the "Reduit". This is a small fort within the fortress, to make a last stand. It also takes care of flanking fire at the back-side of the fortress.
All red lines on the general arrangement, are the brick faces, you see on the next pictures.

I will show the general arrangement several times more, were some orientation might be required.

At number 8 (underside right) we enter fortress and see this Guard building.

Here we arrive in front of number 5.
This is the main Barracks building for the troops.

At first there was only building 6, being the entrance to the Caponnière.

However later on, there was a general requirement for more protection and accommodation for the troops at all fortresses and works in the Dutch Water Line.

So between 1877 and 1885 this "bomb free" Troop Barracks building was made in front of building 6.

The entrances of the existing flanking Casemates for the Caponnière, were also integrated in this new building.

Here you see the main entrance of the new Troop Barracks building.

At the end of the main corridor, in the sun light, the entrance of the Caponnière entrance building is visible.

And even at the end of that corridor the entrance to the Caponnière itself can be seen.

On top of the new building, you see a row of Gun Garages for the guns, that in war time were rolled to open gun positions on the main wall.

Here, we have entered the main corridor and look to the left into the first traversing corridor, that connects all of the many rooms in the Troop Barracks building. 
Here we are looking from the traversing corridor into some rooms.

It is a maze of corridors and rooms, however each room had a specific function.

There are of course many Troop Rooms, that were fitted with simple wooden beds on both sides, furnished with straw mattresses.

There was a hospital, a kitchen, stores, a laundry, toilets, washing rooms, officers rooms, offices and a telegraph office.

Of course there were also gun powder and projectile rooms.

This is the main traversing corridor, connecting the flanking Casemates with the Troop Barracks.

These large corridors were also equipped to house troops, if necessary.

This is indicated by the iron eyes in the walls. These could be used, to hang iron hooks with shelves.
They used the same iron eyes in the troop rooms.

If the enemy reached the Dutch Water Line, the fortress was also supposed, to take inn and reorganize, retreating field army troops, that were operating in front of the Dutch Water Line.

The same as in all other fortresses, the sand layer on the roof was utilized as a drinking water filter.

Here you see a "dripping channel" in the brick work, that leads the filtered water to a water cellar, underneath the ground floor of the Troop Barracks building.

Here you see the crystal clear water in the large drinking water cellar.

It is still good quality drinking water.

Now we come at the end of the main corridor of building 5, the Troop Barracks building.

And go into building 6, the entrance building to the Caponnière.

It is called "Poterne". A Poterne is a ground covered corridor, leading trough a main wall to a front defense area (in this case the Caponnière).

However the Poterne has also rooms next to and on top of the main corridor.
Even troop rooms, because it was actually the predecessor of the new troop barracks.


Here we are coming out of building 5 and look into the main corridor of the Poterne (building 6).

As you can see, the name on the building is "Caponnière", however, it is not the the actual Caponnière, but the corridor, that just leads to it.

Here we look from the ground covered roof of the Poterne building into the gap between the Poterne building and the Troop Barracks building.

We are looking back into the end of the corridor in the Troop Barracks building.

This small gap in the ground covering of the buildings allowed some fresh air and daylight into the buildings.

The chance of an exploding shell dropping into this hole was very small.

Here you see some more of the facade of the Poterne building.

It reveals, that it is not just a corridor, but has also rooms at either side.

Here you see, what is called a "Rifle Gallery", at the front side of the Poterne building.
We are now arrived, between the building 6 and 2.

Building 2, the Caponnière is actually an island in the front moat.

The arrow shaped head is a large earth work body, protecting the flanking gun rooms from direct hits of frontal firing enemy guns.

The arrow shape enables full coverage from the flanking guns of the fortress, making it very difficult to approach the Caponnière island.

Here we are looking back to the Caponnière.

The Caponnière is connected to the Poterne building by a removable bridge.

On the left you see the Poterne building and on the right a small part of the wall of the Caponnière island.

As you see, the front of the Poterne building can be heavily defended from the shooting holes of the Rifle Gallery and from the large flanking fire holes, by small cannons or machine guns.

This would be the case, if the enemy would succeed in getting on the Caponnière island.

This is one of the eight flanking gun rooms in the Caponnière.

Probably, a concentration of 8 cm guns was used in the Caponnière and 12cm guns in the other flanking Casemates.

We are now standing on top of the main front wall of the fortress.
Underneath us is the Poterne buiding.

We now have an overview on the Caponnière.

On the left you see the entrance door.

On the right you see the curved protective overhang of thick brickwork of the gun rooms.

This type of protected gun room is a well known typical in the fortress building art and called a "Reiche Casemate".

Looking from the main wall to the low "Contrescarp" wall along the outside of the moat we see later built concrete Casemates.

A Contrescarp is a wall looking back to the main wall, to cover the moat with small arms fire.


Now we have gone all the way back again, stepped outside the Troop Barracks building and walked to the right, up to number 7.
Here at number 7 on the general arrangement is a separate large entrance into the Troop Barracks Building.

This entrance "Flankbattery 4" was used, to bring guns to the flanking gun rooms for flanking the Caponnière.

At the left end of the Troop Barracks building is of course a similar entrance, called "Flankbattery 3".

Here you see a flanking gun room at the end of the corridor.

The corridor is this large, to enable the guns at that time pulled by 4 to 6 horses, to be driven by the horses into the building, up to the gun position itself.

Later built on the fortress its inner area is this Explosives Storage building.

The building is specially outfitted with a light roof and blast release holes in the walls.

Here you see the Explosives Storage building at number 10.

Now we proceed to no 11.

Near number 11 on the general arrangement, we see the explosives building on the left.

A drive way to a Gun Garage up the main wall, in the middle.

And the entrance to a fortress side Flanking Casemate, on the right.

A Gun Garage or Gun Storage room is called a "Remise".

Here you see the gun position on the main wall, just next to the Remise.

The ground covered remise serves also as a traverse hill, to give the gun some protection against enemy shells.

Here you see an other gun position.

There are 15 gun positions on the main wall of the fortress.

Of which 10 were outfitted with these ammunition storage holes, that used to have sliding doors in front.

Here you see the gun garages on top of the Troop Barracks building.

At the commissioning of the fortress in 1875, the armament existed of:

- 10 guns of 15 cm.
- 29 guns of 12 cm.
- 12 guns of 9 cm.
- 8 guns of 8 cm.

- 27 howitzers of 15 cm.

- 4 mortars of 29 cm.
- 10 mortars type "Coehoorn",

Here you see a map of the complete defense system of the access "Houtense Vlakte" and some fortresses at the edge, that were involved by giving or receiving fire support.

1 = Fort Vossegat (not shown).
2 = The 4 Lunettes.
3 = Fort Jutphaas.
These fortresses are from the first building period and now in second line.
4 = Fort Hoofddijk.
5 = Fort Rhijnauwen.
6 = Fort Vechten.
7 = Fort 't Hemeltje

Blue is inundated area.

On the map above, you see also the so called "Forbidden Circles". To keep a free area of fire, a law of 1853 gave rules and regulations as follows:

Within a circle radius around the fortresses at:

- 300 m; no permanent structures are
- 300 to 600 m; only wooden houses on
  stone foundation are allowed.
- 600 to 1000 m; limited construction.
  Structures are to be suitable to be
  demolished or be burned down
  quickly, at the threat of war.

Nothing to do with that, but on this picture, an artillery equipment shed at Fort Rijnauwen.

This is the Storage building on top of the Poterne building.

You can see a part of the facade of the Poterne building, in the gap between the ground covered Poterne building and the ground covered Troop Barracks building.

Building no. 4, in the center at the back of the fortress is the "Reduit" this was the last retreat, in case the fortress was overrun by the enemy.

As you can see, the Reduit is completely separated from the fortress and has even it's own separate entrance.

It is sticking out a bit in the moat, at the back of the fortress.
This is done on purpose, because in the back corners of the building are Casemates with flanking guns, that cover the moat on the back-side of the fortress.

This is the layout of the Reduit.

The Reduit was also ground covered and had open gun positions on top, as you can see on the elevation pictures on the left.

These show also an hoisting arrangement for hoisting guns up to the roof.

The Reduit is bristled with all kinds of shooting holes.
It is a dangerously dense concentration of gunpowder, guns and men.

Here you see the right flank of the Reduit.

On the left you see the the large shooting holes for the flanking guns of the fortress it's back moat.

At the right, you see the bulge sticking out for flanking of the Reduit it's own moat. 

The sticking out bulges on the reduit are actually flanking Casemates.

The Casemates on the back of the Reduit are both covering the fortress it's back moat with flanking fire, as well as covering the Reduit it's own moat and entrance bridge with flanking fire.

Here we see the back-side of the Reduit, with the bridge and entrance.

Just as with an medieval castle the bridge can be pulled up/

In that time, even defense works had decorations.

The weapon shield with the "W" in the middle is from King Willem the 3rd.

Two Lions of Holland are holding the weapon shield.

Further more there are canon, canon balls, banners and a drum.

Here you see the flanking Casemate at the left back side, with the inner shooting holes for flanking the back moat of the Reduit.
Here we are looking in the main corridor.

At the end we are looking at the rooms of the front flanking Casemate.

Looking back to the main entrance.
These are gun positions of the flanking guns for the Reduits own moat.

You have to bare in mind, that in the time, that the fortress was built, guns were smooth bore front loaders, without recoil damping mechanism.

From 1753 up to 1860 the development of guns had been at a stand-still.
Only after 1860 further development began with the introduction of the rifled barrel and in 1870 breech-loaders were introduced.

Guns used on sailing ships, like you might imagine from pirate movies, were used here. They were tight with ropes to the rings in the wall, to control recoil.

The air vents are later adapted, to serve also as chimney for small wood and coal stoves.
These are the toilets for the men.

There was not much privacy.

A shooting hole, later fitted with glass windows and iron bars.
The stairs to the 1st floor and the roof.

Next to the stairs is the gun hoisting facility.

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Last revised on 24-12-2012