THE TOWN OF LA ROCHE-PONT IS FORTIFIED BY M. DE VAUBAN.

Born at Saint-Leger de Foucheret, in the middle of Burgundy, Vauban, who loved and was well acquainted with this beautiful province, had occasion to visit Roche-Pont several times. The situation of the fortress and its strategical position attracted his notice, and suggested a plan connecting this little town with a line starting with BesanÇon, passing through DÔle, Auxonne, La Roche-Pont, Langres, NeufchÂteau, Toul, Pont-À-Mousson, Metz, Thionville, Longwy, MontmÉdy, Sedan, MÉziÈres, Rocroy, Avesnes, Maubeuge, Valenciennes, Lille, and ending at Dunquerque. The date was 1680; it was a second line. Would to Heaven it had always been maintained by works accommodated to the means of attack! but if the French know how to take, they are but remiss in keeping what they have taken.

The fortress of La Roche-Pont was exposed to attack only from the northern plateau, and the artillery of Vauban's time could make a serious impression only on that side, as the town was protected on its two sides, east and west, by escarpments and two water-courses. Batteries placed on the hills east and west were either dominated by the artillery of the town or must have been placed at a distance of eighteen hundred yards—i.e., out of range—to attain the level of the ramparts. Vauban decided therefore to construct outside the ancient town a large work on the north, which should command the plateau. At the same time—for he was economical of the money of the state—he thought he might avail himself of part of Errard's works, especially the bastions which that engineer had raised on the east and west fronts, and improve the defence of the castle, which would then become a good stronghold. Besides this he planned works, only revetted at the base, along the river, to protect the lower town. On the rivulet side, in like manner, he planned a flanked front for musketry, to secure that side from approach, and to keep some land useful either for the cultivation of vegetables in case of siege, or for pasturage. A weir placed at the mouth of the rivulet, with a flood gate, allowed the inhabitants to inundate the meadows situated on the east of the escarpment.

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Fig. 65.—Vauban's Defences.

Fig. 65 presents the general plan of the works laid out by Vauban. At first he had thought of making on the north, before the front fortified by Errard de Bar-le-Duc, a horn-work before a demi-lune; but he could not thus effectually sweep the divergent points of the plateau. He determined, therefore, on the plan given in Fig. 65, making use of a part of the northern revetments of Errard de Bar-le-Duc. In advance of the northern front, in lieu of the narrow and contracted defences of Errard,[See Fig. 60.] he made a great demi-lune, A (Fig. 65), with a tenaille behind, and next the bastioned work, B, which swept the whole plateau. As to the rest of the town, making use of the old bastions, he strongly flanked them and disposed the stronghold as shown by the plan, D. The roads of the upper town were widened and improved, and the houses detached from the ramparts. The ancient bridge at C had been destroyed by a swelling of the river, and was not rebuilt; but at P, in 1675, a new stone bridge was built, with a tÊte du pont of earthwork. At O a foot-bridge still existed in 1680. The town had again extended along the left bank, and the importance of the citÉ above was diminishing.

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Fig. 66.—Vauban's Outwork.

Fig. 66 presents on a larger scale the plan of the outwork constructed by Vauban. Before the three fronts of this work, demi-lunes with tenailles behind defended the approaches.

Four barracks were built at a. Cavaliers arose on the bastions, and the covered ways, with their places d'armes, were furnished with traverses. In the event of this work being taken, the main body of the fortress could still hold out some days.

Fig. 67 gives the sections of these works, which were cased with masonry, presenting a strong defence which only a regular siege could affect.

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Fig. 67.

But it is desirable to point out the reasons that determined the plan of this work, and the method adopted by the illustrious engineer.

Vauban fortified according to the nature of the position, and was not one of those esprits routiniers who, when once a certain system has made good its claims, insist on applying it on all occasions.

The fortresses, which, like that of La Roche-Pont, are situated at the extremity of a promontory and present only a narrow front to the besieger, assuredly give certain advantages to the defence, since they have scarcely to fear more than one attack and are accessible only on one side; but this position is not without its drawbacks, especially if, as in the present instance, a fan-shaped plateau spreads outside the fortress; for then the besiegers sweep the defences with converging fires, to which the besieged can oppose only a narrow front unprovided with considerable flankments. On the east side the large bastion, in the middle of which Vauban had left standing the fifteenth-century tower, which thus gave him a good revetted cavalier, sufficiently flanked the eastern brow of the outer plateau; but on the western side such a flankment failed entirely, on account of the outward bend caused by the promontory. To obviate these disadvantages Vauban inclined his capital some paces eastwards.[See Fig. 65.]

He had thought at first of suppressing the south flanks of the two extreme bastions, but in that case the exteriors of the east and west faces of these bastions would have been too slanting to sweep the crests of the plateau effectively, while the two curtains answered this object. Besides, the enemy could not then, without risk, commence his trenches on the slopes of the plateau and rapidly approach fronts insufficiently flanked. Vauban therefore set out the plan of the great outwork according to the following method (Fig. 68):—To the outside he gave a length of 180 toises, or 1,156 feet. To the western side, a c, 1,120 feet; to the eastern side, b d, 1,054 feet—that is, he placed the points c and d according with the edge of the plateau; the two angles a and b being equal to one another. On the centre of the side a b of the polygon he erected the perpendicular, e f, having a length equal to one-sixth of a b. From this extreme point, f, were drawn the lines of defence, a g, b h, on which the lengths of the faces of the bastion, a k, b i, were set off equal to two-sevenths of the outer side, a b. To find the flanks of the bastion, according to the method usually adopted in these defences, points k and i, he described arcs of a circle, k l, taking i k as the radius. The point of intersection of this arc with the line b h gave the length and the direction of the flank of the bastion; but, not having been able to trace a regular half-hexagon, and the angles a and b being less obtuse than those of a regular hexagon, by proceeding in this manner, the gorges of the bastion would have been too contracted. Therefore, to determine the flank of the bastion, from the points i and k, he let fall perpendiculars to the lines of defence, a g, b h, and the point h gave the re-entering angle in the curtain, h g, parallel to the side a b. This exposed the flanks a little too much, but enabled them to sweep the outsides more effectively, and in this particular case that was the principal consideration.

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Fig. 68.The width of the ditch of the main work was fixed at 112 ft. 7 in., to the rounding of the counterscarp; and this was determined by a tangent to this rounding, drawn from the angle of the epaule of the opposite bastion.

The ditches being dry, Vauban sunk cunettes in the middle, 23 ft. 4 in. wide and 6 ft. 8 in. deep. Double caponniÈres connected the tenailles with the demi-lunes. The demi-lune was set out as follows:—Taking g k as radius, the arc k m was drawn. Its meeting with the perpendicular, e f, prolonged, gave the point of intersection m, the salient of the demi-lune. From m, the face m n was directed upon a point, o, taken on the face of the bastion at 31 ft. 3 in. from the angle of the epaule, i. The width of the covered way was fixed at 31 ft. 3 in., and that of the glacis at 124 ft. 4 in. The internal places d'armes were 100 ft. across the demi-gorge and 133 ft. 4 in. along the faces. These places d'armes were closed by traverses. The ditch of the demi-lune was 89 ft. 7 in. in width. The tenailles, g, constructed in the direction of the lines of defence, were 43 ft. 9 in. wide at the base.

Cavaliers were made on the bastions to obtain convenient views over the slopes of the plateau. Their faces and sides, parallel to those of the bastions, had to be placed at a considerable distance from the epaulements, in order that the un-cased external foot of the talus might leave the necessary room for the easy working of the pieces of artillery.[22]

The same method was followed for the sides a c and b d. The width of the ditch was increased to 100 ft., and the great demi-lune, t, was so formed that its faces had a length of 332 ft. and its narrow sides 66 ft. The old bastions restored and enlarged, u v, were armed with cavaliers, and the escarp of these bastions was 6 ft. 6½ in. higher than that of the bastions of the outwork,[23] which difference, for that matter, was favoured by the conformation of the ground.

All the escarps and counterscarps were cased with strong masonry, with counterforts in the terre-plein; as shown in the sections of Fig. 67 and Fig. 69.

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Fig. 69.

The works communicated with each other by posterns. As the fortress of La Roche-Pont was only assailable on one side, the number of cannon necessary for its defence might be, it appeared, in proportion to its extent, inconsiderable. The number amounted to thirty twenty-four pounders, ten twelve-and four-pounders to arm the demi-lunes.

At the end of the reign of Louis XIV., the efforts of the coalition were directed towards the north-eastern frontiers, and the garrison of La Roche-Pont did not get a view of the enemy. However, during the course of the eighteenth century, this fortress was kept in passable condition.