Discourses on Fortifications

A geometric diagram showing a circular fortification layout with lines labeled A, B, and C, illustrating the angles and defensive lines discussed in the text.

I will not refrain from saying that these bastions, because each of them has six faces and is somewhat more than circular, are considered by some to be stronger than those that would come with two straight faces. And in truth, the circular shape is stronger than the others, because the entire circumference is equally distant from the center, toward which the material in buildings is restricted, and it ends up providing, little by little, a shoulder to the front part. But in this case, we have no need for the bastion to resist pressure, because it cannot fall inward. Rather, every time the wall offers resistance, the part being struck is not only ruined, but the nearby parts are tormented as well. And because bastions are filled with earth to avoid the inconveniences mentioned elsewhere, whenever their faces have a circular shape on the outside, they will be less able to sustain the weight of the earth that burdens them inside. Therefore, there is no doubt that if straight curtains are struck in the middle of their length and width, they will have shoulders capable of better maintaining the parts above. This does not happen in circular curtains, and provided that the angle formed by two straight lines does not turn out acute, it will be able to resist sufficiently, and furthermore, it will not happen that in the fortress there remains a place that is not seen and defended by all those parts that usually reveal the rest of the faces of the bastions. The angles and circular shapes serve in this case to oppose force, or weight, or the fury of water, earth, or similar things, but in this respect, they do not help on the outer sides to sustain what is inside them. It is concluded, therefore, that the bastion with so many flanks will be very bad, except when making the circular enclosure of more than ten angles, which, as has been said many times, cannot always be appropriate.

Others are of the opinion that, wanting to defend a straight curtain between them from scaling and assaults, of necessity, one flank must ruin or block the other. And to avoid this supposed damage, they would like to proceed as seen in the following plan, where a single shot can clear half of the aforementioned curtains and one face of a bastion. Furthermore, they want a wide shoulder, closed off even in the parapet, and short flanks, with which the orecchioni large defensive ears or orillons, projecting parts of a bastion form right angles on their side, and they make two cannon ports for every square where there are flanks. For each of these, those which are close to the shoulders and orecchioni come to be hidden by them in such a way that they cannot discover all the faces of the opposite bastions from them. Hence, for me to state my opinion on this, I conclude that what is presupposed is out of reason, seeing that enemies, by way of ladders, cannot carry out assaults in places that can truly be called fortresses. Furthermore, assaults both with and without ladders, and batteries, are not made, or better said should not be made, in the curtains between the bastions, just as I have shown elsewhere. This is because, however little the defenders hold back the enemies in the assaults they might want to make in such places, from those parts of the flanks which cannot be seen from the outside, nor consequently removed, they could ruin them all without trouble. Furthermore, even if the enemies had a scarcity of earth or similar things to shelter themselves to get under one or more bastions, they could, by striking the angle of the curtain, cause such ruin that the flanks would not be able to reveal themselves to do their duty, that is, the low flanks. For the high ones could be secured by another route. Therefore, because the flanks are short, and the defenses of the flanks come from further inward due to the orecchioni, and because each half of such curtains is absolutely seen by only one single flank, I resolve to say that I would in no way use such a way of fortifying. Because, besides the things said, that little security that the curtains between the flanks could have would be lost, and the space of the moat contained by the three angles A, B, and the flanks of the orecchioni would remain deprived of defenses.