Thursday, March 21, 2013

I love when it all works out

I've been thinking about the starter campaign I want to write, either for my d100 OSR game, or for one of the retro-clones. I posted the intro fiction a couple months ago. So, a castle gets picked up and dropped somewhere else.

I wanted this to be a small castle. Looking at the wonderful "Fortress Construction" rules from C&S, a Castle I, a castle built up from a shell keep or fortified manor house, seems to fit the bill. A Castle I consists of a keep (40'-50' high, 40'-50' in diameter with 10' thick walls), four 40'-50' towers with 6'-8' walls, 400'-800' of curtain wall with battlements (30'-40' high and 6'-8' thick), a gate with two 40'-50' towers, a portcullis, a drawbridge, and 2 small postern gates, a paved bailey with a small manor house and stables for 30-50 horses, and a moat 20' wide and 10'-20' deep.

That's perfect.

A few weeks ago I drew this map:

Now, if you say the keep is 50 feet across, the outer wall ends up being about 600 feet. (I love GIMP, which gives you a measuring tool.)

Now for the simple Castle I, there are too many gates and towers, as well as more than 200 feet of additional wall. It's also much better protected, requiring an attacker to breach two walls and two gates to get to the keep.

Following the minimal requirements of a Castle I, it would look more like this:

So, the size of the first drawing is correct for a Castle I; it's just a more expensive castle than the minimum.

The C&S chapter "Designing a Feudal Nation" has you decide between an interior or a frontier holding. I decided that I'd use the interior holding numbers, because that would give a little bit more tension to being thrown out into the hinterland of the frontier in a completely unknown place. In a castle of this size,  C&S gives the manpower as follows: a baron, 6 knights, 7 squires (one for the baron), 25 sergeants, 50 men-at-arms, 3 blacksmiths, 2 armorers, 1 scribe, 1 chaplain, 10 mercenaries, 32 petite sergeants, 100 yeomen, and 300 serfs. That's 537 able-bodied men. To get the total population of the fief, multiply by 10 for women, children, and the elderly, for a grand total of 5370.

The next thing I wanted to know is how much farm land does it take to feed that many people. I googled around and found several sources that said in medieval times, it took two acres to feed one person. So, let's see what we need. 5370*2 = 10,740 acres or 16.78 square miles. Let's double that for those areas that aren't being farmed, like forests, rocky hills, ravines, swamps, etc., so 33.5 square miles. That happens to be a circle 3.27 miles in radius, 6.54 miles in diameter.

Wait a minute. How many square miles are in a "6-mile hex"? Finding the formula for the area of a hexagon, I get a 6-mile hex having 31.2 square miles. That's less than 10% off of what we need. So, for my purposes, one 6-mile hex will be the area needed to support my castle!

I really love when it all works out!


  1. Makes you think they might have been using similar numbers when they were putting together their charts.

  2. I find have found the C&S Rules for Medieval Castles and build feudal holdings to be a great resource but at the same time frustrating to use. I guess it is because it seems that sometimes things just do not tie together well. They try to throw so much information at the reader in such a minimal amount of space. I too end up using the Internet for information especially aerial shots of castles and keeps to help understand what the heck they are talking about. It helps to have visuals for the players also.

    I think when creating these castles and keeps we tend to "spread" things out too much. Most castles with their baileys tend to be pretty compact affairs when you look at pictures of actual keeps and castles of the time.

  3. I want to get this castle into my game sometime.