Military Subjects: Organization, Strategy & Tactics


The Ammunition

The Mortars

Système Gribeauval

The Crews

Functioning Principles

Firing Pieces

Preparations

Firing the Mortar

Commands

Towing Mortars

Bibliography

Links


The Siege Mortars and Their Related Skills during the Napoleonic Era

By Marc Morillon

Drawings by Pierre Salamand

Translation from French into English by Paul Morillon

Some of you have probably noticed in "la Cour d'honneur des Invalides", some strange "guns" with a short and wide tube. Those artillery pieces are never worked out by modelers who, by the way, ignore most of their roles and functions. These devices, have nevertheless been extensively used during the sieges of strongholds during the XVIII and XIX centuries. For the First Empire period, which will be our focus now, this materiel deserves to be better known and represented. It has undoubtedly been much more employed in the field than some others which, even though popular, are almost theories such as the well known "Wurst" belonging to the medical services .

The Ammunition

The originality of these artillery pieces lays with their projectiles: the bombs.

Mortar Bombs

Mortar Bombs

There were two different types of bombs at that time:

Cannonballs, solid projectiles, fired by the ordinary field artillery pieces along a straight alike trajectory.

Hollowed projectiles: the "shells", hollowed spheres, iron or cast iron made, filled with powder and set afire by a fuse. When blowing up, they generally set fires as witnessed by General Griois; the shell splinters were far from having the effectiveness demonstrated in more modern conflicts.

Bombs which were hollowed projectiles, even though much heavier (50 to 75 kilos) which added a breaking effect to the burst. This result was particularly sought against buildings during siege operations. The powder load reached 3 to 4 kilos. 

So the bomb was a hollowed sphere, which inner surface was reinforced in its bottom (culot in French) whose role was to sustain the burst pressure. However, there was always the danger that the projectile would explode soon after departure, in which case the artillery piece could be damaged or destroyed. Every bomb was equipped with a fuse, a hollowed pipe made from a lime tree and filled with an inflammable mixture, which length and density were "estimated" by the artificer.

The powder load (we would say the military head today) could also be adjusted to put the emphasis more on the incendiary effect or on the lightening effect for instance. Every bomb was equipped with 2 rings passing through "ears". Those rings eased the transport of the particularly heavy projectiles, with the help of levers and S shaped hooks.

The Mortars

Their look is typical: the tubes are short and huge: calibre reaching 200 to 300 mm. The carriages are bulky; in fact these are sorts of bases able to sustain the almost vertical propelling burst, being understood that the firing angles ranging from 45 degrees, as a minimum, to 60 degrees, the most frequently used. The whole lot, extremely bulky, weighted depending on the calibre, 1500 to 2500 kilos.

There were several types of tubes used during the Napoleonic Wars:

Cylindrical Chamber

Truncated Mortars

Cylindrical Chamber Mortars

Mortars with Truncated Cone Chambers

10 Inch Mortar

Spherical Chamber

10 Inch Gribeauval Mortar

Mortars with Spherical Chambers


 

Tubes with cylindrical chamber, in service at the beginning of the wars with the Gribeauval system (the chamber was designed for a 1 to 2 kilos propelling charge!). With this system, the bomb weight was irregularly distributed in the mortar bore, leaving a gap of about 3 to 4mm with the inner tube, "the wind". One can easily figure out that, in these conditions, the bomb knocked against the inner tube when fired, and that, as a consequence, the tubes were quickly damaged. One artillery piece could fire 48 bombs within 24 hours, but it was wise to limit this rate to 30 to avoid damaging the mortar even more quickly.

To alleviate this disadvantage, the Knight of Gomer, artilleryman and friend of Gribeauval, had conceived truncated cone alike chambers. Therefore, the bomb was laid on a circular fulcrum and was centred. It was also boosted with a more regular thrust around its surface, which provided a fire power enhancement. These "modern" mortars were built from 1791 on.

Let's note finally that some archaic models survived in fortresses, such as the spherical chamber mortars known since the end of the XVII century. Such pieces were still used during the Napoleonic wars. In that case, those were mortars with bases which tube was solid with the carriage and therefore had a fixed tangent scale. They were employed for the defence of fortresses, along the sea coasts, and by the Navy.

Mortiers du Système Gribeauval

Chamber
Calibre
Total Weight
Bomb weight
Maximum Range

Cylindrical Chamber 12 inches

325 mm
2560 kilos
72 kilos
1550 m

Cylindrical Chamber 12 inches

274 mm
2310 kilos
49 kilos
2750 m

Cylindrical Chamber 12 inches

274 mm
1660 kilos
49 kilos
2150 m

Truncated Cone-like Chamber 10 inches

274 mm
2200 kilos
49 kilos
2700 m

The Crews

The gun crews were composed of 5 men. In 1808, one 6 inch mortar type, with a 3 men crew was added to the list. There was also an 8 inch mortar, outside the Gribeauval system. For these small calibres, the bombs could be loaded by one single man and the hooks were not needed.

Functioning Principles

Firing: until the mid XVIII century, the ignition was twofold. The ignition of both the fuse on the top of the bomb, and the propelling powder, required two igniters. One can imagine why this procedure was not only not convenient but also dangerous. Artillerymen then realised that the ignition of the powder contained in the chamber could set fire to the fuse under the condition that some space was left along the inner tube to enable the fire to communicate. This condition was fulfilled when the bomb was steadied with stocks along the inner tube and therefore saved a space, the "wind" to enable the ignited gas to bypass.

Firing the Gribeauval Type Pieces

Aiming the Mortar

Aiming the Mortar

Aiming the Mortar

Aiming the Mortar


Loading the Bomb

Elevating the Mortar

Loading the Bomb

Elevating the Mortar


 

  1. Loading the propelling powder: The tube was elevated to a vertical angle. One man poured the powder in the chamber. It was either a pre-designed charge, contained in a cartridge or a certain powder volume poured out of a bucket, then calculated by the artificer. It was possible to complement the powder charge with earth when firing a small charge.

  2. Loading the bomb: The crew, (1 to 4 to carry the bomb depending on its weight), put the projectile in place, centering it with the wooden stocks. These were driven in with a spatula and a beetle. Once the projectile had been put in place, the tube was slanted to approximately 45 degrees.

  3. Aiming: This critical operation was the bombardier's responsibility. The angle of elevation, combined with the propelling charge, had a direct impact on the fire accuracy. Taking the bearing could be achieved with levers which were placed against the lugs on the outside of the carriage. This operation and the gun's weight required a strong platform, which was made first with a layer of flat stones and then covered with a second layer of timbers (those last ones laid perpendicularly to the carriage axis). The tube could be elevated because of its pivots. The weight was carried by a "coussinet", which slid onwards and backwards underneath. This "coussinet" was carved in order to install an additional piece, "le coin de mire", triangular shaped element which enabled a better adjustment. To aim, two bombardiers took each a lever, reinforced with iron, which they inserted under the "coussinet". A third man, checked the elevation with a compass. The key point was to make sure that the "coin" leant on the "coussinet". Otherwise there was a risk that it could slightly slip and thus change the intended angle of elevation.

According to Manuel de l'Artilleur the following were the procedures for firing the 10 and 12 inch mortars:

Preparations for Loading

On the Left of the Mortar On the Right of the Mortar
2 gunners, 1 artificer
2 gunners
2 levers
2 levers
1 gun's brush, 1 rammer
1 broom
1 drain
1 bucket
1 quick-match bag
1 pipe cleaner
1 pair of long cuffs (the bombardier's)
1 earth filled bag
1 compass, 1 double iron hook
1 spatula, 1 beetle
The bombs were 20 feet behind the battery
1 fuse-chaser
1 portfire 20 feet behind the battery
stocks


Bomb Hooks

Bomb Hooks

The careful reader will have noticed the presence of some strange tools:

The broom: one can easily imagine that when the bomb was fired, incandescent powder pieces fell down on the wooden platform. Under these conditions, handling lightened portfires and powder was dangerous. One gunner was therefore tasked to sweep the surroundings immediately after each bomb departure.

The Bombardier's long cuffs: this man had, amongst other tasks, the critical responsibility to centre the bomb and to chock the stocks. Therefore he had to protect his sleeves when manipulating inside the inner tube.

Bomb's hook: only used for 10 to 12 pounds bombs.


Firing the Mortar

Initial Gunners' Positions

Initial Gunners' Positions

Commands

The following commands were given to fire the mortar:

"Front" Everybody faces the mortar.

"Approvisionnez" The mortar is laid on its front "coussinets". The tools are stowed away.

"Aux leviers" The gunners take up the levers.

"Embarrez" The levers block the screws.

"En Batterie" The mortar is put in place on its platform with the 4 levers. The bombardier, standing behind direct the gunners.

"Dressez le mortier" The bombardier, has his left hand laid on the top of the mortar and his right hand on the ear, while the gunners help him with the levers. The mortar is then steadied in front and behind with a "coin de mire".

"A la poudre, à la bombe" The loaders start when given the signal by the left side gunner. The first gunners take up the bomb with the hook and face each others, on the left side of the mortar. The one who is the closest to the mortar handles the smaller end of the lever. The bombardier goes to the depot, takes the cartridge and comes to take his position before the first right hand gunner.

"La poudre dans le mortier" The bombardier climbs on the carriage, and pours the powder in. It is compressed with the rammer. The rammer is put back on the trestles.

"La bombe dans le mortier" The four gunners lift up the bomb. Then, they carry the buckets/baskets containing the tools, in particular, the stocks.

"Baissez le mortier" This manoeuvre is executed with the levers.

"Aux leviers" The bombardier take the compass. The gunners keep the levers which will be used for the aiming

"Donnez les degrés, pointez" Two levers underneath the mortar tube will be used to elevate the tube to the right angle, while the bombardier checks the compass and directs the gunners. Two levers are inserted underneath the carriage notches on the rear.

"Posez vos leviers" The levers are left aside (note from the translator).

"Dégorgez, amorcez" The bombardier clears the way with the fuse chaser in the left hand and put the quick-match in, with the right hand. The second gunner on the right covers it with the earth filled bag. The first gunner on the right sweeps the platform.

"Au boute-feu; Marche; Front Boute-feu; Marche" One gunner drops down the earth filled bag. The bombardier goes on the right or on the left to monitor the centering of the bomb.

"Haut le bras" The first gunner thrusts out his arms while holding the portfire, takes one step backwards with the left foot and bends the right knee. He bends down and brings the portfire to 4 fingers off the aperture, nails over, right arm stretched, left arm bound to the body along the thigh.

"Feu" The gunner ignites the quick-match. This move is dangerous, since the gas pressure blowing out of the aperture can break his arm.

Towing and Moving the Mortars

Moving the Mortar

Moving the Mortar

It is easy to figure out that this type of equipment, extremely heavy and without wheels, was difficult to move. For long distances they where mixed with the siege teams, equipped with the tremendous 24 pounds' guns, designed to breach down walls. Special harnessing were used. Tubes and carriages were transported together or separately, depending on their weight, on "mortar lorries", 2 wheeled vehicles, towed by 4 horses in single file. These transport dispositions were also of more practical use for moving within the trenches during besieging operations. The unloading was done by tipping out the lorry. Putting the gun on its carriage required lifting crabs. The bombs were transported in ammunition carts, trailer typed vehicles with rails. One could also use smaller means: cannon balls carts or even bombs' hand-barrows, which were similar to stretchers.

We have seen that most of the systems in use during the Napoleonic wars were relatively outdated, and therefore some tentative improvement were undertaken. The Peninsula War and in particular during the siege of Cadix (which lasted for more than 2 years) spurred the creativity of two artillerymen. Sénarmont and Villantroys explored the way to build long range mortars. Those almost revolutionary devices were used with variable success, but that is something for another article.

Bibliography

Le Blond, M. L'artillerie raisonnée Paris; 1761.

Duturbie, T. Manuel de l'Artilleur Paris An III de la République.

Aide mémoire des officiers d'Artillerie Paris; 1809.

Les canons de Valmy Booklet by the National French Army Museum (Les Invalides).

Links

"Le Bivouac" is a French association of miniatures collectors and modellers, which is settled around Toulon and Hyeres, but gathers members and associates from everywhere in France. Privileged ties are also maintained with Italian and Spanish enthusiasts. You can contact us at: "Le Bivouac"

Placed on the Napoleon Series: February, 2000

 

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