Discourses on Fortifications

...and each of the aforementioned things, both separately and unitedly, implies, in order to be able to better use them in needs and occurrences. Nor would I heed the words of those who say that by drawing the faces of the bastions from some part of the curtains that are between them, one does not fail to make the flank of just size. For these people do not measure by effects what can truly be demanded as just size in a similar matter. They do not realize, I say, that the length of the flank is one of the causes of the greatness and perfection of the building. Therefore, being able to make retreats original: "retirate" and other necessary things inside the building, one will be able to give that treatment and damage to the enemy that is appropriate, just as one who has judgment and knows what the length of time can bring will be able to consider. Moreover, from the large flank, one can not only make counter-battery for some space of time to whomever would want to ruin or block it, but also defend each bastion from far out. Consequently, the forces of those inside cannot be as easily disordered as when the flanks were smaller, for when these were beaten down, the defenders would be forced to retreat further inside the enclosure and leave defenseless those faces of the bastions that stood less long.

A geometric diagram of a bastion fortification, labeled with points A, B, C, D, H, and other markers, illustrates the layout of flanks and faces.

It is true that although, as I said above, the flanks are better the larger they are, one nonetheless tends to leave them thus for less expense. This is because, so that their size does not force the bastions to become acute, it would be necessary to make the enclosure circular and of more than eight angles. Returning to my purpose, I do not believe it can be denied to me that it is better to make bastion G, because it is larger and better in the exterior angle, than bastion H for the reasons I have often assigned.

But because everything needs a limit, and it could be said to me that the size of the flanks should not go to infinity, I would resolve that when, due to the capacity of the place one wishes to fortify, the enclosure becomes circular and of more than six angles, the flanks should be made at least twenty canne long, turning the faces of the bastion toward some part of the curtains in such a way that the exterior angles result in being more obtuse than right. Nonetheless, he who has to fortify must look well at what I said above, so that in avoiding one evil, he does not stumble into a worse one, especially since one can have the same intent by making embrasures in the width of the shoulders, as I have demonstrated elsewhere. In this case, one increases—without more expense or alteration to the buildings—about twelve canne of flank, that is, six on the shoulder at least, and six by entering the flank further inside the enclosure, for the effects I have demonstrated elsewhere. Thus, in this order, by using the shoulders, they can more reasonably be made parallel on the inner parts with the curtains that are between the bastions, as I have demonstrated elsewhere. And if I were to make embrasures in the shoulders, or let us say cheeks original: "guance" for the aforementioned effect, when the enclosure was such that, even if the faces of the bastion were turned toward some part of the curtains, the bastion arrived at perfection, I would like it all the more to do so when it became acute. I would take care, however, to make the flanks of such size that, with the plazas consequently being large, one can, as is already said, hold off the enemy. Since one knows with evident reason that the more the flanks are primary defenses, the more one must attend to their safety and strength, knowing clearly that if the bastion is small, a powerful enemy can more easily—not only with cannon fire but without battery, when he has the convenience of earth or other material to shelter himself—nullify the defenses and ruin that part of the bastions that pleases him most.