There still appears to exist great misapprehension with regard to the siege operations now going on in France. Some of our contemporaries, The Times for instance, incline towards the opinion that the Germans, excellent though they be in the field, do not understand how to carry on a siege; others suppose that the siege of Strasbourg is carried on for the purpose not so much of getting hold of the town as of making experiments and exercising the German engineers and artillerists. And all this because neither Strasbourg, nor Toul, nor Metz, nor PhaIsbourg has as yet surrendered. It appears to be completely forgotten that the last siege carried on previous to this war, that of Sebastopol, required eleven months of open trenches before the place was reduced.

To rectify such crude notions, which could not be put forth but by people unacquainted with military matters, it will be necessary to recall to them what sort of a proceeding a siege really is. The rampart of most fortresses is bastioned — that is to say, it has at its angles pentagonal projections called bastions, which protect by their fire both the space in front of the works and the ditch lying immediately at their foot. In this ditch, between every two bastions, there is a detached triangular work called the demi-lune, which covers part of the bastions, and the curtain — that is, the portion of rampart between them; the ditch extends round this demi-lune. Outside this main ditch there is the covered way, a broad road protected by the edge of the glacis, an elevation of ground about seven feet high, and gently sloping down externally. In many cases there are other works added to complicate the difficulties of the attack. The ramparts of all these works are lined at the bottom with masonry or protected by water in the ditches, so as to render an assault on the intact works impossible; and the works are so arranged that the outer ones are always commanded — that is, looked down upon — by the inner ones, while they themselves command the field by the height of their ramparts.

To attack such a fortress the method perfected by Vauban is still the one made use of, although the rifled artillery of the besieged may compel variations if the ground before the fortress be perfectly level to a great distance. But as almost all these fortresses were constructed under the reign of smooth-bore artillery, the ground beyond 800 yards from the works is generally left out of the calculation, and in almost every case will give the besiegers a sheltered approach up to that distance without regular trenches. The first thing, then, is to invest the place, drive in its outposts and other detachments, reconnoitre the works, get the siege guns, ammunition, and other stores to the front, and organize the depôts. In the present war a first bombardment by field guns also belonged to this preliminary period, which may last a considerable time. Strasbourg was loosely invested on the 10th of August, closely about the 20th, bombarded from the 23rd to the 28th, and yet the regular siege began on the 29th only. This regular siege dates from the opening of the first parallel, a trench with the earth thrown up on the side towards the fortress, so as to hide and shelter the men passing through it. This first parallel generally encircles the works at a distance of from 600 to 700 yards. In it are established the enfilading batteries; they are placed in the prolongation of all the faces — that is, those lines of rampart whose fire commands the field; and this is done upon all that part of the fortress which is subjected to attack. Their object is to fire along these faces, and thus to destroy the guns and kill the gunners placed upon them. There must be at least twenty such batteries, with from two to three guns each; say fifty heavy guns in all. There were also usually placed in the first parallel a number of mortars to bombard the town or the bombproof magazines of the garrison; they will, with our present artillery, be required only for the latter purpose, rifled guns being now sufficient for the former.

From the first parallel, trenches are pushed in advance in lines, the prolongation of which does not touch the works of the fortress, so that none of the works can enfilade them; they advance in zigzag until they arrive within about 350 yards from the works, where the second parallel is then traced — a trench similar to the first, but shorter in length. This is generally done the fourth or fifth night after the opening of the trenches. In the second parallel are established the counter-batteries, one against each of the attacked faces, and nearly parallel to them; they are to demolish the guns and ramparts face to face, and cross their fire with the enfilading batteries. They will contain in all about sixty guns of heavy calibre. Then, again, the besiegers advance by new zigzags, which become shorter and closer together the nearer they come to the fortress. At about 150 yards from the works the half-parallel is dug out for mortar batteries, and at the foot of the glacis, about sixty yards from the works, the third parallel is placed, which again contains mortar batteries. This may be completed on the ninth or tenth night of open trenches.

In this proximity to the works the real difficulty begins. The artillery fire of the besieged, as far as it commands the open, will by this time have been pretty nearly silenced, but the musketry from the ramparts is now more effective than ever, and will retard the work in the trenches very much. The approaches now have to be made with much greater caution and upon a different plan, which we cannot explain here in detail. The eleventh night may bring the besieger to the salient angles of the covered way, in front of the salient points of the bastions and demi-lunes; and by the sixteenth night he may have completed the crowning of the glacis — that is to say, carried along his trenches behind the crest of the glacis parallel to the covered way. Then only will he be in a position to establish batteries in order to break the masonry of the ramparts so as to effect a passage across the ditch into the fortress, and to silence the guns on the bastion flanks, which fire along the ditch and forbid its passage. These flanks and their guns may be destroyed and the breach effected on the seventeenth day. On the following night the descent into the ditch and a covered way across it to protect the storming party against flanking fire may be completed and the assault given.

We have in this sketch attempted to give an account of the course of siege operations against one of the weakest and simplest classes of fortress (a Vauban’s hexagon), and to fix the time necessary for the various stages of the siege — if undisturbed by successful sallies — on the supposition that the defence does not display extraordinary activity, courage, or resources. Yet, even under these favourable circumstances, we see it will take at least seventeen days before the main ramparts can be breached, and thereby the place opened to an assault. If the garrison be sufficient in number and well supplied, there is no military reason whatever why they should surrender before; from a merely military point of view it is nothing but their duty that they should hold out at least so long. And then people complain that Strasbourg, which has been subjected to but fourteen days of open trenches, and which possesses outworks on the front of attack, enabling it to hold out at least five days longer than the average — that Strasbourg has not yet been taken. They complain that Metz, Toul, PhaIsbourg have not yet surrendered. But we do not yet know whether a single trench has been opened against Toul, and of the other fortresses we know that they are not yet regularly besieged at all. As to Metz, there seems at present no intention to besiege it regularly; the starving out of Bazaine’s army appears the most effective way of taking it. These impatient writers ought to know that there are but very few commanders of fortresses who will surrender to a patrol of four Lancers, or even to a bombardment, if they have anything like sufficient garrisons and stores at their command. If Stettin surrendered in 1807 to a regiment of cavalry, if the French border fortresses in 1815 capitulated under the effect, or even the fear, of a short bombardment, we must not forget that Woerth and Spicheren 14 together amounted neither to a Jena 35 nor to a Waterloo 56; and, moreover, it would be preposterous to doubt that there are plenty of officers in the French army who can hold out a regular siege even with a garrison of Gardes Mobiles.