General rule to spacing towers on a medieval city wall

Question

I'm workshopping a medieval fantasy setting and one of the primary locations is a large port city, located on a bay out to the ocean.

I'm still early in development, but since this settlement is quite large and located relatively close to borders with another country, I'm working out its defenses, the big one being its defensive walls. Among the details I'm a bit stuck on for the walls, is the towers. Specifically, how spaced out they should be. Obviously nothing's a perfect square or circle, but is there a general estimate on how spaced out the towers should be, relative to the estimated length of the wall?

Answer 1

The spacing of towers along medieval curtain walls was typically to provide flanking fire along straight sections of wall.

In order to provide proper flanking fire, it would be necessary to situate these towers a distance apart that is less than or approximately equal to the effective range of the missile weapons in use at the time at which the fortifications were built. The OP would have to decide what missile weapons are in use and what their effective ranges were.

For example, longbows had an effective range of up to 250 metres against massed enemies, and crossbows had an effective range of 100m. The towers would be spaced accordingly so that troops on one tower could shoot enemies at the base of a neighbouring tower. Of course, closer spacing would allow more accurate missile fire against enemies.

As pointed out in comments, walls that are not easily approchable may have few, if any, towers for flanking fire. Such towers were primarily built on easily approchable sections of wall.

Answer 2

From 30 to 150 meters, but 60 meters or less seems to be often preffered in big cities

The citadel of medieval city of Carcasone has wall in length of 3km with 52 towers, which would give you the average distance of around 60 meters, during the Roman times the spacing between the towers of castellum were between 18 to 30 meters.

14th century fortification of Vyšehrad in Prague had 15 square towers spaced 60 meters apart plus two fortified gatehouses.

Wall of Philip II Augustus in Paris built between 1190 and 1213 had 77 circular towers in 60 meters intervals. Wall was considerd adequate long into 15th century.

Forification of Brussels in 14th century was 4km long and had 40 towers and 7 fortified gatehouses, that gives an average of 85 meters.

Of the walls of Tallinn built in 12th century there is 1850 meters still standing today with 26 towers, that is average span of some 70 meters.

Based on tourist information a wall in Rothenburg has 4 kilometers and 42 towers, which would give an average interval somewhere under 100 meters.

City of Krakau was fortified in 13th century by 2km of wall with 50 towers and 8 gatehouses - average of 40 meters.

City of Citadella has its walls built in 13th century in total lenght of 1461 meters and has 32 towers evenly spaced at around 45 meters.

Based on those examples I dare to say that in medieval Europe, if city was sufficiently wealthy it aimed to one tower at least every 60 meters.

You can browse the List of walled cities for more inspiration. (beware not all listed has medieval fortifications)

Answer 3

In addition to @MontyWild's excellent answer, consider the practicalities, too.

• Your city/town doesn't have an infinite amount of money or resources. That means that, while the ideal would be to space them such that a ranged weapon could hit the next tower in either direction, there's a good chance you can't afford to build or maintain that many. That means you need to think through placement of the towers using other considerations like the terrain outside the town and what's inside the town (e.g., how easily an area could be accessed if the wall is breached or whether or not what's in that area deserves special protection or could be used to your advantage if the wall is breached).

• Your city also doesn't have an infinite number of people to man those towers. At least one defender per tower. Probably more. In shifts. They all need to be fed and supplied. That really adds up (see bullet #1) and your town might not have that many people to spare.

• Towers are often a function of the wall's engineering and not a function of the wall's defense. Some medieval walls had ramparts, meaning the towers themselves weren't that important in terms of defense. What they really were, were places where the rest of the wall could anchor. Corners, places along long lengths. Either side of gates, etc. In this case, defenders are firing ranged weapons from any location along the rampart and the towers, if they have any meaning to the defenders at all, are simply a nice place to store supplies or stack the dead wounded.

• You don't tell us whether the walls are made of wood, dirt, or stone. Medieval walls were made from all three basic resources. If you really simplify history, you'll find mounded dirt first, wood bulwarks second, and stone third. You won't have towers with mounded dirt. You didn't see a lot of towers with wood, but when you did, they were always at critical structural points. It's the stone walls where you might see towers placed purely for defensive purposes.

What all those bullets are telling you is that you need to view a bigger picture than just defense. In fact, I suspect that if you look at real medieval wall design, you'll find that nearly all towers served structural purposes before they served defensive purposes. In summary:

• Where do you need towers to make your wall structurally sound?

• How much money/resources do you have to spend constructing and maintaining towers?

• How many defenders can you really supply to staff all those towers?

Answer 4

The Great Wall of China spaced its watchtowers anywhere from three miles to over double that depending on terrain.

Work out what the towers are for and then space them appropriately. If the wall itself is your primary fighting platform, then the towers don't need to be close together. If the towers are more important fighting platforms then you need them within bowshot of each other at the very least so they can support each other.

With long border type walls towers are mostly for housing the defenders and storing ammo and supplies, perhaps some artillery. The wall itself would be taken before anyone bothered attacking the towers. They're expensive to build and maintain and of limited value.

If you have unlimited resources then Byzantium would be another option. It was a fully fortified port city with towers about 60 metres apart which could support each other. It withstood sieges repeatedly and some armies just looked at the fortifications and turned around and went home again. But this level of protection was only possible because it had the resources of an empire behind its building.

Answer 5

If the wall is round, ever expanding peripherary needs more towers per unit of length. Draw a circle with scale radius. Bigger your settlement the more towers you need.

Generally, there are no rules regarding the overall distance between towers of a castle or fortified city. Towers were put in the walls at a necessary point, so guards would have a good view on the surroundings. If it's one person per tower, best case scenario is One tower every 100 feet. According to Guinness World Records. The normal intelligible conversation via outdoor range of the adult male human voice in still air is 180 m (590 ft 6.6 in). For defense that's long.

Another strategy is have NO towers except at points of entry like gates. And have a battlement fully walkable by personnel. But hidden behind wall so guards cannot be seen.

Answer 6

Tower + Archer Radius intersects with Tower+ ArcherRadius. Point of intersection distance to wall is within half-archer distance from wall?