A military dictionary

by William Duane

It is not, however, my design to throw works of this kind into utter disrepute. There are situations and local circumstances, which not only make their adoption useful, but render it absolutely necessary. I cannot pretend to describe the specific nature of such exigencies, as they grow out of existing cases, which an able general and an engineer will know how to discriminate by examining the ground.

The ditch belonging to the body of the place, be its soil what it may, must be very broad, as the chief security to be derived from it, depends entirely upon its width. The enemy cannot easily fill it up, and he must suffer a considerable loss of men, should he attempt to cross it; being exposed to the discharge of artillery from the flanks, which artillery cannot be dismounted from any quarter or lodgment, before the counter-guards are taken. The storming of the place must depend entirely upon the previous conquest of the side ravelins, and of the centre half moons; for unless the enemy has first effected this, he will not be able to cross the ditch, or make any lodgment, since at every approach he must be annoyed from the flanks, and battered in front; he must, in fact, attack and get the better of five works at once. The execution of any part of so important a task, must be the more dangerous, because in proportion, as he overcomes one line of defence, another presents itself which is equally formidable, and the rest increase in difficulty and hazard.

When I submitted this new method to the consideration of able and intelligent men, only one opponent started to controvert the property of its general adoption. This was a celebrated Dutch engineer, who asserted that it could not be of any essential service, except in hexagons, or figures that had many sides; he further argued, that the method was more faulty in small works, because the angles became more acute, and that no use could be made of them in regular fortification.

I had the good fortune to satisfy this gentleman, and to convince him, that his objections were not well founded. I stated to him, that by increasing the width of the ditch at the angle of the flanks of the bastion, I reduced that angle to any size I judged necessary; I maintained, that by so doing I did not weaken the place; but that on the contrary by cancelling the parallelogram of the counter-guards, I rendered more oblique any battery which the enemy might erect in front of the bastion, whilst the rampart belonging to it fell under a cross fire from the mitred half-moon.

With respect to its uselessness in irregular fortification, after having discussed the subject at some length, I got him to agree with me, that every detached piece of fortification might be constructed any where (and with greater advantage to the ultimate defence of a place) sooner than in plain counter-guards, horn or crownworks, tenailles and such like fortifications, because by means of the retreat which was secured under a second line of retrenchment, by means of the regular resistance it afforded, without having one dead angle attached, and by means of the little ground it left for the enemy to lodge on, the main body of the place was more effectually protected, and the approaches of the enemy were considerably checked.

With regard to the construction proposed in this new method, I take all the measurements, and I mark all the essential points upon capital lines; that is to say, I prolong the lines of the saliant angles of the bastion, and those of the centre of the curtain; after which I determine the width of the ditch at 23 or 24 toises, in order to make the parallels of the faces of the different bastions for the counterscarp of the counter-guards and of the great half-moon, and finally the thickness of the works, to agree with the ditches in front.

With regard to the ravelins which are made between the mitred half-moons and the counter-guards, I place the saliant angle in the centre of the scite, and I construct faces to them in such a manner, that they are under a straight line of defence from the half-moons and counter-guards. I erect the counterscarp and glacis in the usual manner, only with this difference that I wish to have a ditch of moderate breadth and depth between the covert-way and the glacis: say, two toises broad upon two deep.

In order to clear the ditch of occasional rubbish that may fall in, or of pieces that may drop from the demolished parts of a fortification during a siege, square excavations or wells must occasionally be made along the flanks and faces of the different works; by which means the ditch is always kept clean, and you may at any time repair the fortifications, whilst on the other hand, the enemy, should he attempt to storm the place, must have recourse to fascines, as he could derive no advantage from the materials that would otherwise be found under the walls.”

This ingenious writer has described every part of the method proposed in a clear and perspicuous manner. His plan is particularly valuable, on account of the exact measurements it contains, whereby the most common understanding may become acquainted with the construction. He appears singularly anxious to have it practically proved, that works can be erected according to this method at a less expence than by any other, and that there is no comparison between the advantages it affords in point of real utility. In chap. 16, p. 61, the following account is given of his second system, which he calls the Great System.

“After I had thoroughly digested my plan, relative to the best method of covering a town or fortified place by outworks, it naturally occurred, that I had not provided the necessary means of keeping the troops under shelter, of securing a retreat to the artillery, which is always seized whenever a work is taken by assault, nor of furnishing a heavier discharge of ordnance and musquetry than the enemy could pour in. These important objects put my invention to work, and I directed all the faculties of my mind towards discovering a kind of fortification which might not only cover the body of the place, and by a new disposition of its relative parts communicate equally with every quarter, without there being any necessity to carry the heavy ordnance into the ditch; but likewise oblige the besieging enemy to increase his means of attack, and make extraordinary efforts. I necessarily saw, that the saliant angles of the bastions should be well covered, and that the strongest ought to be raised before the curtain belonging to the body of the place, in order to force the assailants to make their attack on a quarter from whence the concentrated fire of several works, presenting a wide front of artillery, would issue with considerable effect.