Building the Fort Beauséjour

I've been learning about the construction of Fort Beauséjour lately. It's a pentagonal fort, that follows a standard simple-bastion style designed by the French military engineer Sébastien Le Prestre, Seigneur de Vauban, commonly known as Vauban. His designs set up basic and advanced principles for all defensive structures to be built under the French Empire, Beauséjour being one such example.

In the text Fire and Stone: The Science of Fortress Warfare 1660-1860 by Christopher Duffy, the author goes into a fair amount of detail as to how and why these forts were designed, how they were situated.

[Image from Fire and Stone: The Science of Fortress Warfare 1660-1860. Duffy, Christopher. 1975.]

Where the Fortresses Were Built
Relevant to Fort Beau is the section on Ground. "The healthiness of the site is one of the most important single considerations which determined the position of the fort. Swampy sites were notorious for killing off the garrison." The fort is surrounded by the Tantramar marshes, though elevated on a small patch of firm soil, the trees and scrub cut away by the Acadians. The advantage of a site like this is that the fort can only be attacked from a few (dry) points, allowing a smaller garrison and upkeep. With every yard of swampy ground approached on the fort, its strength increases proportionally. However, in The Siege of Fort Beauséjour, by Chris M. Hand, the author states that the fort was actually poorly located, being too far from the water to have any impact on shipping along the river, and too far forward on the slope to defend the crest.

[Image from Forts of Chignecto, Webster, John Clarence. 1930.]

How the Fortresses were Built
Once the principle of building or extending a fort was made, costs, memorandums, drawings, shape and properties were all drawn up. They made clear the relationship of the fort to the whole of the countryside, to the distance of a cannon-shot. In drawing their plans for a new fortress, engineers began with the center point, where an average even ground was thought to be best and then determined the main direction of attack to set up the front entrance. In this pentagonal fort system, the engineers would have a set of large scale drawings on a rotating table situated at the very midpoint of the site. They would then extend a chain connected to a peg right in the center of the actual drawing and align it with points in the drawing. Once aligned, the worker would place a picket in the ground and continue through all the major points of the five bastions as per the engineer's drawing.

[Image from Fire and Stone: The Science of Fortress Warfare 1660-1860. Duffy, Christopher. 1975.]

Depending on the hardness of the soil, different foundations were laid. At Beauséjour, the soil must have been hard enough to be able to use a less severe foundation system otherwise used in marshy areas. In those sites, long vertical spikes are driven into the ground, attached to a timber raft system upon which the bastions are placed. Instead, it uses a gabion system, which is essentially baskets filled with stone (which come from a nearby quarry) and placed over a simple timber raft system, then backfilled with earthworks. The gabions are an extremely versatile 'material' to work with, and will very likely become one of the primary building systems for my proposal. (Herzog and de Meuron used a gabion system for the Dominus Winery in France in 1997). The gabions are an economical and sustainable solution, perhaps better suited for non-military applications, given their tendency to collapse under cannon-fire.

[Image from Fire and Stone: The Science of Fortress Warfare 1660-1860. Duffy, Christopher. 1975.]

Drawing the Fort
Learning to draw a pentagon is not the most difficult part about starting a site plan -- it's figuring out which system the first engineers used to draw the pentagon. There are more than eight systems (see this website to gauge their complexity). What I'm learning is that the memory of this place is quietly being spoken through its geometry.

[Image from: The Siege of Fort Beauséjour 1755. Hand, Chris M. 2004.]

As I've sketched out above, these concentric circles which are used to construct a pentagon fit exactly to the edge of the site's ridge. This means that that proportion would determine the overall size of the fort and construction thereafter. In knowing the approximate size of that initial face (known as the line of defense), laying out the pentagon with pegs can commence. A revealing difference of rationality: the French built the south-facing line of defense as their main entrance which faces the direction of attack. After its capture, the British reversed the fort, moving the entrance to the back and converting the old entrance into a cannon battery, allowing full control of the ridge.


A lot is written about the difference of quality in leadership between the French and British at the fort, and this is an additional distinction, for what it's worth.