Concerning different types of curtains, and their deficiencies and inconveniences. Chap. VII.

MANY say that for two reasons many have built bastions distant from one another by two hundred canne a unit of measurement, approx. 2 meters, because by using fewer bastions to defend a place, one could enclose much territory with less expense. The other reason is that the heavy artillery used in the flanks to defend the space between every two bastions would not have, at such a distance, the force to break the opposite flank when the shot arrived. And in order to guard the faces of the bastions, they made cavalieri raised defensive platforms in the middle, and on the half of the curtains that are between them, or they fixed other flanks in them for this effect. But these reasons seem very poorly founded to me, just as they do to many others. For if one makes the calculation, one sees that it would cost more to build four bastions with four cavalieri in the middle and eight hundred canne of curtains than to build six hundred canne of curtains and six bastions, which would be so close to each other that they would comfortably defend one another. They would be more perfect, and more space would be enclosed. Furthermore, one should not presuppose that the enemies will place themselves between the flanks except when they have reduced them to the point of being unable to perform their duty. In that case, besides the fact that it is not necessary to speak of ruining one another, it is clear that the enemies could enter through the batteries already made without having to exert new efforts to enter through the curtains between the bastions. But when the flanks are not impeded, they would notice and ruin either themselves or the flanks every time they wanted to enter through the middle curtains. Therefore, I will say nothing more about this, since it is seen that at present, little account is taken of such an effect. Added to this is the fact that the defense that arises from those cavalieri, coming from above and exposed, is not good. And if one wanted to defend the bastions from other flanks made in the long curtains, as I have said according to their reasoning, the flanks themselves would end up ruining one another every time one wanted to defend the space in between them. But because various people have used various types of curtains and other structures between the bastions, I will discuss each one individually so that one may have particular knowledge of them. Among these, I primarily like the curtain in a straight line, provided it is made of such a length that with real cannons one can break or harass quite vigorously the shelters that the enemy usually makes to approach the faces of the bastions. For with less expense and more speed, one will have within the fortress the capacity one desires.

A geometric diagram showing the layout of a fortification wall (curtain) between two bastions, with lines indicating angles of fire and defensive coverage.

Some, by making the aforementioned curtain longer and dividing it into three equal parts (or a little more or less), and drawing the middle part inward as seen here below, have made in it two flanks that must clear the faces of the bastions. And so that the bastion becomes less imperfect, they leave as much length to the aforementioned flanks as to allow for moderate shoulders and enough space for a cannon port. It seems to them that in order for these to come between other flanks, large shoulders are not necessary. And wishing for greater width in the squares, they provide it in one of the two following ways seen in the following plan. These ways have been observed by many to widen the squares and ensure that the artillery has its due recoil in every direction. The utility they claim is derived from this method of building is this: the defenses are doubled, and consequently, difficulty is increased for the enemy, because the flanks of the bastions can be given more trouble if they have entered some ruined point of the bastion. And it seems to me that even if the intention to increase defenses in fortifications is a laudable thing, one must be careful that the effect succeeds in fact and not just in name. This is because if one proceeds as seen in the following plan to increase defenses, and especially on the faces of the bastions which are doubly defended in the manner I have stated from above, the following bad effects arise from this belief. Namely, four flanks appear on one facade, which would cost more to build and maintain. And those bastions that are formed at the angles of the enclosure, whether closer or further from each other, would always be less good for the reasons I have indicated elsewhere. Besides this, less square space would remain within the enclosure than could reasonably exist. And to ensure the bastions do not become sharp, even if the space between them were one hundred and fifty canne long, it would nonetheless be necessary to make the enclosure circular and of seven equal angles and sides, and twenty-eight flanks, which for many reasons might not be appropriate, especially when the fortress turns out larger than desired or the site does not allow for the aforementioned circular enclosure. And to be brief, I omit a few little things about this that seem to me of little importance, and I conclude that to add defenses to the faces of the bastions, I would take a method far removed from this, as I will demonstrate in another place in these discourses.