_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.
[Illustration: 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,[57] 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.
[Illustration: 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.
[Illustration: 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.[58]
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.
[Illustration: 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.[59]
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. 6-1/2 in. higher
than that of the bastions of the outwork,[60] 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.
[Illustration: 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.
FOOTNOTES:
[Footnote 57: See Fig. 60.]
[Footnote 58: See Fig. 65.]
[Footnote 59: See Fig. 67, the section on E, F.]
[Footnote 60: See Fig. 67, the sections on G H and I K.]