Fortifications and siege works. (American
Construction of fortified bridgeheads (têtes du pont).
In the centre of the second row is an excellent representation of a horn work.
(American Artillerist’s Companion)
ESTIMATED REQUIREMENTS TO DEFEND FORTRESSES
When a man has committed no faults in war, he can only have been engaged in it but a short time.
The ring of hammers and other blunt objects, heavy digging
of field fortifications, many times under fire, the building of gun platforms
in almost every type of terrain, including muddy, flooded ground, marked the
beginning of a siege of a fortress or a strongly fortified city or town.
Engineer officers would direct the beginnings of the siege with their templates
and instruments, calculating mathematically where to dig and, with their
brothers of the artillery, where to emplace the siege batteries to bring the
fortress under punishing fire.
Engineer troops, the sapeurs du génie and miners, would
prepare their work, the miners getting ready once again to sink their shafts
and begin their tunnels toward the fortress to their front and preparing the
mining charges that could bring down the curtain walls confronting them. The
sapeurs would don their blackened armour, cuirass and lobster helmet, that
might, or might not, protect them in the besiegers’ trenches against gunfire
from the defenders, and prepare to dig saps and parallels and perhaps lead the
With the initial saps and approaches dug, the first
batteries established with their wooden firing platforms and magazines, the
great guns would be brought into position by horse- and man-power, within range
of the opposing fortified positions to begin their relentless pounding of the
enemy positions both day and night. Siege guns, 16- and 24-pounders, coupled
with 8-inch howitzers, would blast the defenders and the great mortars, lofting
their deadly bombs over the fortress walls and into the interior would search
for the fortresses’ magazines for a lucky shot that might end the siege.
Last of all, but not nearly least, the infantry battalions,
when not engaged in digging the siege entrenchments in support of the
engineers, would wait until summoned to assault breaches made in the fortress
walls if the fortress did not capitulate before that was necessary. The ‘poor
bloody infantry’ would bear the burden, and pay the price in blood, for any
failure of the engineers, artillerymen, and the senior officers if the siege
had not been properly handled before the infantry were sent in.
With the advent of gunpowder artillery in Europe in the
fourteenth century, a balance was usually attempted, and many times achieved,
between firepower and mobility. Field artillery came into its own by the middle
of the fourth decade of the eighteenth century, pioneered by the Prussians,
with the Austrians making similar changes in the next decade. The French
followed in the mid-1760s after humiliating defeats in the Seven Years War that
clearly demonstrated the inferiority of the then-current Vallière System of
Artillery of 1732. Just about every other nation with an interest in artillery
followed suit, including the young United States upon declaring independence
from Great Britain in 1776.
Heavy artillery, however, was present from the dawn of the
arm, and that was a function both of technology, or lack of it, and the need to
have guns strong enough to punch through or partially demolish both permanent
and field fortifications. Heavy artillery is the main subject of this volume,
with its strength and lack of general mobility and inability to keep up with a
fast-moving field army being its main characteristics.
The main opponent of siege artillery was fortress or
garrison artillery, usually composed of the same guns as siege artillery, but
mounted on different gun carriages, designed to be operated inside
fortifications and to defend the position where they were emplaced.
Siege and fortress artillery also included howitzers and
mortars. The howitzers used in siege and fortress operations were of the same
general design as those assigned to the field artillery, but were larger and
heavier, with the same restrictions on movement as siege artillery guns.
Mortars were stationary artillery pieces, designed for the attack and defence
of fortified places, and ranged from small to large and generally speaking
fired explosive shell. Howitzers were something like smaller mortars, but
mounted on field carriages, and were somewhat more mobile than the mortars.
All siege artillery would be mounted in batteries supervised
and constructed by the engineers and artillery officers, and great wooden
platforms would be emplaced from which the artillery could fire from a stable
Sieges were usually carefully undertaken, meticulously
planned, and were methodically carried out with the besiegers’ trenches and
batteries edging ever-closer to their targets and objective. While the
artillery rate of fire might be much slower than that of field artillery in
battle, it was relentless and would continue day and night until a breach was
made in the curtain wall or the defenders finally capitulated.
The initial siege works and artillery batteries and firing
positions completed, sweating gunners manhandled their large, awkward siege
pieces onto the firing platforms, managing to get the long gun tubes into the
embrasures cut into the field works without damaging the entrenchments.
Ammunition would be moved into the magazines constructed in the rear of each
siege battery position, dug in and protected from enemy artillery fire.
Artillery implements would be placed in each gun position, for the gun crews to
use in pointing, loading, and cleaning each piece. The gun crews were smaller
than those for field artillery, even though the heavy siege guns were both
physically larger than the field pieces, and the guns themselves were of larger
Large mortars were emplaced in some of the siege battery
positions. Of larger calibre than even the largest of the siege guns, mortars would
lob bombs over the walls of a besieged fortress, town, or city. These were huge
compared to the ammunition fired by the siege guns – some weighing in at 200
pounds. Their crews were also smaller than those in the field artillery, as the
mortars were stationary weapons, the guns tubes emplaced in their ‘beds’ –
heavy, awkward mounts. Whereas the siege guns were on the familiar wheeled gun
carriages which could be moved as necessary, the huge-mouthed mortars would
have to be moved by specially constructed vehicles from place to place, and
then assembled in their prepared firing positions.
Together, the mortars and heavy siege guns, usually known as
‘battering pieces’ would concentrate their firepower against a pre-selected
point of the besieged place to prepare it for an infantry assault or to batter
the garrison into submission.
Fortress and Siege Fortifications and the Attack and
Defence of Places
The fate of a nation may depend sometimes upon the
position of a fortress.
13 October 1810, Sobral, Portugal
Chef de Bataillon Jean Jacques Pelet, first aide-de-camp to
Marshal André Massena, commander of the Army of Portugal, and his companion,
Capitaine Jean Richoux, made their way towards Sobral by taking a steep and
narrow road up to a position from where they could observe the British
fortifications that were becoming known as the Lines of Torres Vedras.
While the road had been repaired in places, it was a
difficult climb that was hard on the horses, and by the time they reached their
objective, only one of the dragoons remained and his mount had thrown a shoe.
Pelet and Richoux dismounted and were guided to the top of a hill by some
Portuguese peasants, who were, however, very closed-mouthed even as to the
names of the villages in the area.
Being an engineer, Pelet closely inspected the terrain and
noted that the French maps were inaccurate and needed to be updated. French
troops were occupying the area, and Pelet and Richoux picked up another escort,
this time of voltigeurs. These light infantrymen, often called kleine Manner
(‘little men’) in contemporary comments, were efficient and excellent escorts
for the type of terrain the two staff officers had to negotiate on their
The defences were extensive, and were manned by both
Portuguese and British troops, and they would definitely be a hard nut to crack
if Massena chose to assault them. A mixture of fortifications had been
constructed – redoubts, lunettes, redans and trenches criss-crossed the rough
terrain, and all of them appeared to be mutually supporting.
When he had seen enough, Pelet motioned for them to go, and
he and Captain Richoux with their escort of vigilant voltigeurs, made their way
back down to friendly territory. Massena would not like their report, but would
take it to heart and no doubt, as per his usual practice, he would make his own
reconnaissance. Massena was no fool. He was a good commander who could be
ruthless when need be, but he would not waste his troops in useless assaults
against what appeared to be an impregnable position.
Since the dawn of warfare, man has attempted to protect
himself and what is his with some type of fortification. Alexander and his
near-invincible Macedonians were successful in the attack of fortified
positions, be they temporary or permanent. The Romans were excellent military
engineers and understood in depth the defence and attack of places. In the
Middle Ages the fortified castle could sometimes withstand a siege, especially
if the garrison had enough provisions and access to a potable water supply. With
the introduction of gunpowder artillery in the fourteenth century, castles
could now be breached more easily, and it was gunpowder artillery manned by the
Ottoman Turks that finally defeated the walls of Constantinople in 1453,
arguably the most sophisticated defensive system up to that time, the Eastern
Romans being the capable inheritors of the Roman ability and flair for military
Recognizing that modern artillery had rendered the older
systems of fortifications obsolete, such military engineers as Vauban and
Coehorn developed fortification systems that were lower, harder to breach, and
usually were organized and defended in depth.
There are generally speaking two types of fortifications –
permanent and temporary. Permanent fortifications usually took the form of the
large masonry defences of fortified cities and major fortresses. These required
constant maintenance because if left alone they would fall into disrepair.
Despite their imposing appearance and apparent strength and impression of
solidity, masonry and brick fortifications could be quite fragile. Temporary
fortifications took the form of earthworks, and these could be built for use on
a battlefield and take the shape of anything from a strong redoubt, to redans,
flèches, and lunettes that would be hastily constructed in a battery position
by artillery gun crews. Some temporary fortifications could be used as
semi-permanent structures, such as those used to fortify a bridgehead, or those
made in the breach of a besieged fortress after an artillery bombardment had
punched a hole in the curtain wall.
Interestingly, earthworks were also used in permanent
fortifications either to enhance the masonry works or to repair them. They were
also used to construct new defensive works during a siege to replace works that
had been breached or destroyed.
Siege works were also semi-permanent field fortifications
and were constructed of earth and wood. Siege batteries would be built of earth
reinforced with gabions or wood. Embrasures for the siege guns would be earth
reinforced with wood. and the gun platforms inside the works, essential for
stable firing positions for siege artillery, were constructed of wood.
Fortresses filled more roles than merely defensive
structures. They served as depots and magazines and would be filled with
supplies during a campaign, especially along an army’s line of communication.
They could be garrisoned by regular troops, but these would usually be
forwarded to the field army, and their place taken either by recruits or
conscripts who would then complete their training before being sent forward as
replacements when needed or requested.
Fortresses were usually ‘easy’ to defend against an
attacking or besieging army, and it was a long, tedious process for an army to
prepare to besiege a fortress, especially a fortress city. Just to invest and
surround a fortress took a large number of troops and units, and it also took
time to prepare the siege works. Many times defences had to be prepared by a
besieging army to protect itself from an army marching to relieve the siege.
Sometimes, sieges would be lifted by the besieging force having to march
against an enemy army intent on relieving the fortress, which was done during
one of the British sieges of Badajoz in 1811, resulting in the bloody battle of
Albuera between Marshal Soult’s French and British General Beresford’s British
When gunpowder weapons, especially artillery, were developed
in the late Middle Ages, all existing fortifications soon became obsolete. What
resulted was a new range of permanent and field fortifications which, if not
impervious to artillery fire, then at the very least made it more difficult for
artillery to breach permanent defences. The use of earthworks became more frequent
over the years, but permanent masonry fortifications were developed that would
give the defender at least a chance of withstanding modern artillery fire.
Overall, one of the best concepts of defensive works was to
construct them in depth which gave the attackers the problem of overcoming
defences in layers and in order to accomplish that mission they might incur
heavy enough casualties to cause the siege to fail.
The great objective of fortifications and the artillery that
one employs as the principal agent of their defence is to make one’s troops,
which are inferior in numbers, in morale, or in skill of manoeuvring, more able
to resist another’s troops which are superior in one or another of these
points. The success of the defence depends, therefore, on the ability of the
general, the strength of the fieldworks, the proper disposition of the troops,
and the effective use of the artillery.
Permanent defences would begin from the inside and be
constructed outward. Geometrical patterns were used to construct bastions along
the curtain wall which had interlocking fields of fire against any attacker. In
front of the curtain wall, redans would be constructed as outworks, not
attached to the bastions or curtain wall. A ditch, either dry or wet, would be
constructed in front of the curtain wall and the interlocking bastions. This
was designed to impede any infantry assault and would make the curtain wall
even taller to the assaulting infantry if they reached the ditch. The ditch
might have a palisade in the middle to impede any assault further. Inside the
main fortress, a citadel was usually constructed which was the last line refuge
for the garrison which they would fall back to if the curtain was breached and
the enemy infantry assault was successful.
How the available artillery was employed was critical to the
defence of the place:
In the case where one places the cannon at various points
in the entrenchments, it will be necessary, as much as possible, that they not
get in the way of the infantry, or diminish the execution of their fire. In the
entrenchments, as everywhere else, large batteries should not be made, because
the enemy can simply avoid them. They often lead to defeat, for they strengthen
one point of the line while weakening the rest, which can be all the more
dangerous if the number of pieces is very considerable.
Vauban also believed that artillery was critical for the
defence of a fortress and should be the main emphasis by the defenders. He also
pushed for the development and production of iron fortress pieces, as iron was
much less expensive than bronze, but his recommendations were ignored by the
Duc de Main, who was the Grand Master of the Artillery during that period.
Finally, it should be stressed that ‘The science of
fortification was by no means unknown and uncultivated long before … Vauban.’
The first publication describing a complete system of fortification was written
by Errard de Barleduc who served Henry IV, the first Bourbon king of France.
Subsequently, the Chevalier Antoine de Ville wrote a treatise of fortification
while serving Louis XIII as an engineer. De Ville’s methods were termed ‘the
French system’ and he was not only a theorist, but a practitioner. The ‘Dutch
system’ was developed by Samuel Marollois, whose writings influenced Maurice of
The Count de Pagan was Vauban’s ‘direct ancestor’ in the
science of siege warfare and probably served as a model for Vauban. Pagan was
both experienced and knowledgeable and his conduct of sieges during the reign
of Louis XIII was successful. Pagan’s system was ‘improved upon by Alain
Manesson Mallet, and his construction of fortification is … looked upon as the
most perfect’ and was little different from Vauban’s first system and was
probably the model for it.
Menno, Baron Coehorn, the great Dutch engineer and
contemporary of Vauban, has already been mentioned; he was at the same time
general of artillery and lieutenant general of infantry in the Dutch service.
He was also Director General ‘of all the fortified places belonging to the
United Provinces’. Coehorn was noted as being ‘intelligent and sagacious’, as
well as ‘thoroughly convinced, that, however expensively the rampart of a town
may be constructed, it could not long sustain the shock of heavy ordnance’ and
he ‘invented three different systems, by which he throws so many obstacles in
the way of a besieging enemy, that, although the place be not in reality
rendered impregnable, it is nevertheless so far secured as to make its conquest
a business of considerable hazard and expense’. It should also be noted that
Coehorn designed his systems to defend Holland, a country that is generally
flat and level and so could tailor his fortifications to that one reality.
Vauban did not have that luxury. When the two actually faced each other in the
attack and defence of places, at the siege of Namur in 1692, Vauban’s system
proved to be superior to Coehorn’s.
While fortresses were not the main focus of campaigns during
the French Revolutionary and Napoleonic periods, they were still useful in a
number of ways. Holding key fortresses in an occupied territory or country was
a constant reminder to the population at large that there was a garrison,
usually a large one, that could become hostile and a major problem in the event
Occupying and maintaining fortresses in one’s own nation
provided a shield or covering force behind which the army could mobilize and
take the field. Well-garrisoned and provisioned fortresses supplied with enough
artillery could pose a major problem to an invading army, usually so much that
forces had to be left behind, or the enemy commander believed that they had to
be left behind, to invest the fortress and either nullify it or take it. This
could lead to the invading army’s strength being depleted to such a point as to
leave it too weak when it finally came up against the defending army.
Fortresses also provided a safe and sheltered environment
where recently conscripted units could complete their training before becoming
part of the field army. And those garrisons of conscripts could be a reassuring
reminder both for the native population and the enemy that the garrison could
become a hostile force if provoked. Napoleon used this approach during his
Coastal defences were necessary for the protection of naval
bases, ports, and other facilities deemed essential. The fortifications were
usually nothing out of the ordinary and generally followed the patterns
developed by inland fortifications other than that they also had to be able to
defend themselves against attacking ships if necessary.
One interesting development by the British was the Martello
Tower. Built on the coastline, these were round, two-storey masonry structures
with a flat roof, upon which would typically be placed one coastal defence
piece, either a naval long gun or a carronade. The piece was usually put on a
traversing gun carriage that could be pointed in any direction in a full
circle. They could be a standalone work, or be coordinated with other defensive
measures and they were built in Britain, Canada, and other places in the
British Empire. While small and usually armed with only one garrison piece,
they were quite innovative, easy to build and man, and if nothing else could
provide early warning of a naval or land attack.
Coastal defence ordnance was normally, but not always, of
the iron naval type. The gun carriages used with the ordnance could be of
several types, including the standard naval gun carriage of the truck type, the
traversing carriage, or the older slide carriage. Mortars could also be used in
the defence of ports and naval bases.