[Award Winner] Fortifications I: How to build a fortress

**Hoel** · 01-08-2009, 10:21 AM

So you decided on fortifying! To add some defenses. Good decision but, Hey, you ask, I don't know where to start!
Fear not grasshopper. I will tell you what you need.
First off; you have to decide what defenses you need. Will your map be a city with a ring wall against raiders, and to controll import/export tariffs? Will it be a fortified city that could stand a seige? Will it be a fortress in it's own right?
This essay will deal with all those issues, but we'll start out with the basics, then look at the fortress.
The basics of fortification comes down to defensivness versus investment. Walls, towers and fortressess are very expensive. The project can become on the order of pyramid building in its scale.
Carlsborg fortress in sweden used up 250 000 metric tons of limestone for its land front and the 5 kilometer walls covering the waterfronts required enough earth to build 20 pyramids. In a fantasy world, much of this can be fudged, so no problem, a few lines on a map won't cost you anything, but keep this in mind. Use an engineers perspective rather than the designers. The designer adds until there's noting more to add. An engineer will take away until there's nothin more to take away.
Now, let's talk about what a wall is and why you'll want one. A wall is a man made obstacle to prevent someone from accessing a place. In fortification terms, it should keep the enemy outside your defended area and stack the odds against him. Common planning says an enemy force must outnumber the defenders by at least three to one for a successful siege or assault on a fortified target.
The fortifications are also platforms where your ranged weapons can work against the enemy and protect the target from the enemies ranged weapons. The medieval walls were build high and thin, with crenelation at the top to give the archers protection. Towers gives the archers added range and fields of fire. A wall must be in the fields of fire from as many different places at once as possible, but the archer at the top can't fire straight down, so the towers portruded from the walls (called hanging) to give fields of fire along the walls.

**Hoel** · 01-08-2009, 10:23 AM

Let's build a fortress to see the different defences at work.
First we build a keep, It's a big fortified tower or house. This is the last line of defence and where the object of defence is kept, wether it's a noble family, a treasure, the villagers or just the place itself. The perfect location is on ha hill, it's always much more difficult attacking uphill. In the early middle ages they often build the hills themselves, these are called mottes.
To add a layer of defence we add a wall outside the keep. It could go around it or be attached to the back wall of the keep. The area enclosed are called a courtyard or a baily. We now have a good defense from the early middle ages called a motte-and-baily.
We do have one big gaping hole in our defense, the entrance must be a hole in the wall. A wall with a hole is an invitation for attack, even with a big heavy door, it's the most voulnerable spot. So we thicken the wall around the gate to twice the thickness of the walls and put a tower on top. Now we have a gatehouse. The tunnel that runs through it can be gated at both ends, filled with logs and debris and from the second floor, holes in roof of the tunnel (aptly called murderholes) can be used to tip boiling water, flammable oil or stones and arrows onto the packed assault force. The gate is secured.

**Hoel** · 01-08-2009, 10:24 AM

The next problem is the corners and fronts of our walls. A long stretch of flat wall can be broken with a ram or with siege engines. To shore up this weakness we again thicken the walls at intervals and put towers on top. Ideally we should have as short stretches of flat walls as possible, but here's the effectivness vs cost dilemma again.
Next we have the the corners. They have good fields of fire, but are a weak point. To solve the problem and give us a bit of adge, we put some even bigger and heavier towers, right at the corners. These are called bastions and can be as big as the keep itself.
Now we have a small fortress. Let's keep going shall we. We'll add another layer to the defenses.

**Hoel** · 01-08-2009, 10:27 AM

We'll add a moat to our fortress. There's two kinds. The dry moat, more or less a big ditch that adds problems for seige towers and ladders. We can also make a wet moat, that's a channel filled with water, this is can be a wholly man made afair, with stagnant rain water but it's not very good, a dry season can make it a dry moat fast. If we have access to a river or stream we can use it to fill the moat.
I if the enemy breaches the first wall they're in the fortress and we have lost. If we add another layer to the fortress, they will have to breach both walls to get in.
First, lets make another wall. It will use the terrain to force the enemy to attack uphill where possible (never below a slope, always on the top) and make use of natural water for a ready made moat. The courtyard of this layer of wall will probably house some of you essential services so make some room, but not too much. If the enemy breaches the wall instead of going over and taking them from you, you will still have defenders on the wall to combat them and you will want to keep the enemy in reach of as many of your defences as possible. If you have room.
Now add the gatehouse and the towers as before, minimizing open stretches of wall. To give the attackers a harder time, make the way from gate to gate as long as possible. Put the gate opposite to the gate to the main fortress, or seal them in with a wall so that they have to go around an almost complete circle.
Finally, we can make one more addition to this layer. If they think it's difficult to breach one gate, why not add two. Put a small courtyard right behind or in front of your main gate and add another gatehouse.
This process can be repeated for a third layer.

**Hoel** · 01-08-2009, 10:27 AM

There's also a few additions to your fortress that can be used when the shape of the wall or terrain is suitable.
I you have a wall where your defenders have a shorter range, you can extend the range of your defense with a barbican. The barbican is a heavy bastion outside the walls connected to the walls with a walkway or a wall.
Multiple small couryards can be contructed by addong walls between the layers. Each courtyard can be defended separatley.
Putting the gates in a slope allows the defenders to roll logs or burning hay-bales through the gate onto the assaulting forces.
Smaller fortresses outside the main fortress on strategic locations is called block-houses or redoubts and can be used to defend choke points.

This is the end of this first chapter on my essay on how plan fortifications. My final note is about how you plan a map.
When you sketch it out, think about how the city grows and plan the defences for each stage, don't be afraid to leave some parts of town outside the walls. Think defensivly and plan your walls to be as effective as possible as cheaply as possible.
Any fort will be built as tight as possible with most of the city outside. A ring wall can be put up around the whole town, but is not the main defense, it's there to ward off raiders and to keep a siege protracted.
Oh. and a round shape is more cost effective than a square.

**Redrobes** · 01-08-2009, 11:24 AM

Well said Hoel,

Castles changed shape considerably over their period of existence depending on the weapons and technology available at the time but we tend to focus on castles where the crossbow and siege engines were the best that could be had. As soon as powder came in they all changed shape.

I can add just one or two more points. Bastions were at corners and along the flat parts of a wall and were used to pack troops into so that they could fire parallel to the adjoining wall. When ladders and assault towers were placed against the wall then you could get some fire onto them without leaning over the top of the wall and getting shot up.

Also, whilst a round outer wall is efficient money wise, a castles main weakness is through a siege where a curtain of men prevented food and supplies getting in. A ring is also the most efficient shape for them too. So in latter periods some castles had spiky bits of fortifications protruding from them so that the circle of men one bowshot distance from the castle had to be that much bigger and therefore harder to maintain and costly to siege. Dover castle has an excellent example.

http://maps.google.co.uk/maps?hl=en&...06545&t=h&z=18

Another thing which you touched on is about moats. Water filled moats were employed mainly to suppress sappers. These were chaps which burrowed under the outer walls and tried to destabilize them into falling down or in rarer cases burrow a tunnel fully under. Thats why most curtains and towers have wedge shaped bottoms to them. The water filled moat serves to drown sappers so that they cant start a tunnel.

The whole topic goes on and on tho eh ? Its the to-ing and fro-ing of the arms race.