Guest Question: Fortress artillery

John Grenier (that’s GREN-ee-er or GREN-ee-ay, as you like it) asked a question in the comments, so I’ll move it here for greater visibility. I’ll give my answer in the comments, and others can chime in as well.

“OK, so I’m looking at the Oct 1756 intelligence reports from Rogers’s Rangers on the forts at Crown Point and Ticonderoga. One of RR’s prisoners reported that Ti held 33 guns (12 18#ers, 12 15#ers, and 9 8#ers) and Crown Point held 18 total, with 18#ers being the largest. I know that is miniscule compared to the numbers in most forts in Flanders, but then again, Crown Point and Ti were (are?) in the middle of nowhere. I wonder, is there some kind of ranking order (1st-rate thru 6th-rate, etc.) for forts, no? Where would a fort with 33 smallish guns, and another with 18, fall in the scheme of things? Of course, these were pretty much stand-alone operations — no mutually supporting forts (unless you consider Ti and CP), garrisons, and magazine systems to help in times of siege. It’s clear by the fall of ’56 that the earl of Loudoun (the Britrish CINC) knew he did not have the transporation system that would allow him to get enough men, guns, and materiel in front of the forts for a siege (yet Montcalm was able to do so the next summer, and had already done so at Oswego). Anyway, just looking for a little context, and I figure this is a good place to ask. Cheers”


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One response to “Guest Question: Fortress artillery”

  1. jostwald says :

    There was no way of ranking the size/strength of a fortress in the age of Vauban à la ship rates, although in the 1770s you have someone like Fourcroy de Ramecourt trying to calculate a “moment de fortification” that would precisely quantify the cost of a fortress relative to its ability to resist attack (duration of defense). You could attempt, like one modern engineer has done, to make comparisons by measuring angles and perimeters, but I haven’t seen contemporary engineers do that. For most of the early modern period you had the basic distinction between fort, citadel, and town walls, and even there it didn’t tell you much about their relative strengths within each category. Unlike ships that could be designed according to a single basic plan, engineering manuals paid much attention to irregular fortresses that had to deal with the terrain, with constant reminders that there were no ‘rules’ to follow in such cases. I’d argue further that well into the 18C even the military engineers were a surprisingly a-mathematical bunch (beyond geometry and some trigonometry) – read about the French corps’ reaction to Bélidor in the 1720s for example. The same thing was true for the artillery engineers, witness Benjamin Robins’ ballistics test taking place in the late 18C as well. In other words, they didn’t apply formulae to their work until at least late in the 18C, so even the engineers probably didn’t have the mental mindset to think about quantifying their fortresses with precision.

    That being said, they did rely on approximations, and had a general sense of which fortifications were strong and which weak (although here too the plans could differ radically from the reality on the ground, and recall my book’s discussion of the difficulty in determining the strength and weakness of any given front). But to stop being a contextualizing academic and get to your point, there were various rules of thumb regarding the number of guns and men for a fort, usually based on the number of bastions. Here’s a table from Vauban’s late treatise on the defense:

    In the notes the editor says Vauban’s recommendations are a bit much, suggesting only 8 cannon per bastion. It gives other details, including the fact that some of the smaller cannon would likely be used in the outworks. A Dutch document from c. 1700 gave the same numbers as Vauban’s table.

    This was totally theoretical however: the number of cannon (and their positions) weren’t fixed like they were on a ship – even their location could change if they fired à barbette (over the top) or cut embrasures into the earthen ramparts, and they needed to change if they weren’t to be quickly put out of service. The number of cannon also depended on whether they were mounted on fortress/naval vs. field carriages (or could be switched) and therefore whether they could be enlisted into field service. When a garrison’s performance was judged, the main question was whether they had enough men to man the perimeter or not; the number of artillery pieces was rarely mentioned.

    Modern historians of the trace italienne focus a lot on the angled bastions and artillery fields of fire, but contemporaries c. 1700 tended to not talk about the garrison’s artillery very much – it was a real quandary whether to use them and lose them, or try to keep some in reserve to defend the ditches and face complaints that you were keeping them shiny for the new occupants. Rather than focus on artillery, contemporaries instead emphasized the number of men (and, by extension, their muskets). The distance between each point of a fortification (e.g. from one bastion to another) was designed to be mutually supported by *musketfire* from the flanking works; these would be serviceable long after the garrison cannon on the ramparts were dismounted or made inoperable from besieger fire. That’s why, when you add in the gunpowder mines and handgrenades, I’ve always considered it better to talk about ‘gunpowder fortresses’ rather than ‘artillery fortresses.’
    Hope this helps.

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