Early Modern Military Architecture

Apr 2018
279
USA
#1
Since the Early Modern period has it's own subforum I thought I'd make a general thread about fortification design as sieges during the era.

To start with, here's the link to transcript of a short, 10 page treatise published by Sir Balthazar Gerbier in 1649 which goes over the basic rules of fort design in the mid 17th century:

https://quod.lib.umich.edu/e/eebo/A...d+science+--++England+--++Early+works+to+1800

the reference illustration from the last page:
fetchimage1.png

a couple of notable passages:

"
There are two sorts of Fortifications in generall, one the ancient, and the other moderne:

The Places that are fortified according unto the ancient manner, are those that have single Wals onely, and with Towers at certaine distances, made of Materials that are not capable to resist the Canon▪ and their Towers being too small as that they cannot beare any Canon; Those kinde of places deserve not to be said fortified ones:

The Modernes are those which are flancked on all sides, and that the flancking and flancked bodies are so solid and of such matter as that they may resist the Canon.

"

"
To flanck himselfe well according unto the Principles and Maximes of this art, there must not be one point in all the circuit of the figure of a Regular, or Irregular place, which ought not to be seene within, and that the Line whereby self defence is intended, bee not above 200. paces, a measure which is prescribed by divers that have fully obtained the practicall Part, for that it would import very little to see an Enemy from within a place if he wereso faire distant that you could not offend him, and by the mouths of your Mus∣kets to make him retire.

In this matter four things are necessary; the defence of a place to consist of the Musket and not of the Canon, for that a Canon requires too many attenders, consumes a great deale of munition, is easily dismounted, uneasie to raise againe, and will not endure a continuall fire. . .

"
 
Apr 2018
279
USA
#3
Is he really saying 'Don't put cannon in fortresses?'
Not quite. The idea was that the fortress should be designed so that it can be defended using only small arms if need be.

Even if the top of the of the wall was damaged by enemy bombardment the defenders could always quickly move a bunch of musketeers back into position and begin emergency repairs. However if the outside of the wall has been collapsed enough that a cannon has started to slide downwards, then even if the gun itself hasn't been destroyed its shear weight would tend to make it very difficult for the defenders to hoist back into position.
 

Chlodio

Ad Honorem
Aug 2016
3,831
Dispargum
#4
Given enough time, a fortress will fall. The only way to save a besieged fortress is for a friendly army to march to its relief. The purpose of a fortress is to delay the attacking enemy. Everything about fortress construction should be based on the idea of prolonging the siege. Cannon help by keeping the enemy back some distance, at least as long as the ammo holds out and the cannon remain operational. It's inevitable that sooner or later the cannon will be dismounted, but in the meantime, the siege is being prolonged.
 
Jul 2009
9,782
#5
@hborrgg:

I am not familiar with Balthazar Gerbier. Did he have experience of war or was his treatise more theoretical in nature?

A good monograph on early modern fortification is C. Duffy's Siege Warfare: The Fortress in the Early Modern World, 1494-1660. Gerbier is mentioned one time as an example of Continental practice copied by the English, but nothing else is to be found there.
 
Mar 2014
1,894
Lithuania
#6
In most cases besieging army cannot stay and besiege fortress indefinitely. In early modern period this time period is actually quite short, disease and famine will force besiegers to retreat even if there is no strong opposing force.
 
Apr 2018
279
USA
#7
I am not familiar with Balthazar Gerbier. Did he have experience of war or was his treatise more theoretical in nature?

A good monograph on early modern fortification is C. Duffy's Siege Warfare: The Fortress in the Early Modern World, 1494-1660. Gerbier is mentioned one time as an example of Continental practice copied by the English, but nothing else is to be found there.
He apparently grew up in the netherlands during the 80 years war and spent a lot of time studying the fortifications there, which was about a good a school as any. I mainly just picked this one out because it was fairly short and focused. The same site also has a translation of Vaubaun who goes into much more detail: https://quod.lib.umich.edu/e/eebo/A47731.0001.001/1:11?rgn=div1;view=toc;

I agree on Duffy's Siege Warfare book, that's a really good one.

Given enough time, a fortress will fall. The only way to save a besieged fortress is for a friendly army to march to its relief. The purpose of a fortress is to delay the attacking enemy. Everything about fortress construction should be based on the idea of prolonging the siege. Cannon help by keeping the enemy back some distance, at least as long as the ammo holds out and the cannon remain operational. It's inevitable that sooner or later the cannon will be dismounted, but in the meantime, the siege is being prolonged.
That's true. Although this sort of gets into another reason that man-portable weapons tended to play a bigger role for the defenders during a siege than heavy artillery. Cannons could harrass the enemy at long range, they were very terrifying, and they were very good at stopping attackers that were scattered and disorganized. But with their low rate of fire, they still usually weren't able to stop a determined, well-ordered assault column from getting from A to B without significant obsticles like ditches and walls in the way. And once the besiegers heavy artillery got within 150-200 yards or so there was no fortification that could survive long before eventually being breached.

A solution to this was to focus on many different layers of defense starting with various outworks, then ravelins, then ditches, then the bastions and curtain walls, and then potentially further lines of defense inside the walls (one of the main reasons given for starting to prefer relatively low main walls, aside from them having a lower profile, was that if you were forced to retreat inside the town and start tearing down buildings and barricading streets to create new lines of entrenchment, the enemy wouldn't have as much of a high ground advantage once they did take those curtain walls. Each layer would typically be actively defended by the garrison to some extent so that even if the enemy managed to successfully assault one line of defense, their attack would usually run out of steam while the defenders simply retreated to their fallback positions. This would force the besiegers even if they had a very large and well-equipped army to engage in a long, drawn out slog as they slowly take one layer at a time over the course of weeks or months while always having to worry about sudden, surprise sallies by the defenders trying to delay them further or even retake ground that hasn't been properly secured yet. This sort of active defense though relied much more on small arms or at least very light artillery, since heavy cannon couldn't easily be advanced to forward positions if needed, and if a position was overrun, it would be impossible for heavy artillery to withdraw without being captured.

Here's a couple more illustrations this time from William Garrard in 1590:




And here's a neat cross-section of a large ditch and rampart drawn by Robert Ward in 1639 showing multiple figthing positions:
 
Nov 2010
7,547
Cornwall
#8
In most cases besieging army cannot stay and besiege fortress indefinitely. In early modern period this time period is actually quite short, disease and famine will force besiegers to retreat even if there is no strong opposing force.
Yes indeed and this can extend back into the medieval. In Iberia for example where supplies were low and transport very difficult, if the besiegers had no siege equipment and the castle had half decent walls and position, a very low garrison would suffice and, during their time, Templar garrisons could be of 30 to 50 in this region.
 

Frank81

Ad Honorem
Feb 2010
5,004
Canary Islands-Spain
#10
Early Modern military engineers were obsesed with Geometry

Fortification was greatly advanced thanks to their works in proportion, distances and angles

However, sometimes this led to excess. For example, the common Spanish way to fortify was a square with bastions. But top engineers of the second half of the century thought the ideal shape was a triangle (the lesser possible surface to defend) and so Felipe II ordered a lot of triangle fortress. For example, Nova Arx, the brand new fortress that defended Tunis, is a double triangular fortress with six bastions (similar to the Star of David)



In La Goulette, two triangles protruding the front were built, against the opinion of military veterans, who argued this exposed the troops too much




The French used this system as well, for example the Fort Caroline in the US





The massive defeat of Tunis-La Golette of 1574 made clear the weakness of such device. The defence was too complex. After then, the fortress were designed according to the traditional Spanish square with four bastions, as in San Marcos