Mortars & Infantry Guns

Of the legion of weapons deployed during the course of World War Two, the mortar was the most despised by the foot soldier.  It was, if  I recall correctly, the single biggest killer of infantrymen throughout the war.  Yet it was one of the simplest devices to be found on the battlefield.

The mortar had first appeared in the Great War, but during the inter war period the design was updated by the Brandt company.  The weapon comprised just three parts; a barrel, a bipod leg assembly and a heavy baseplate.  The mortar bomb was simply dropped, tail first, down the barrel.  At the base of the barrel was a firing pin.  This ignited a charge in the tail of the bomb which in turn detonated the propellant charge.  The bomb was then shot out of the barrel and the weapon was ready to fire again.  There were no spent casings to extract and eject, no moving parts to oil, nothing to rely on other than gravity meaning the bomb fell down the tube and concussion ensuring the charge detonated.  Ranging was achieved by manipulating the elevation and the size of the propellant charge.  

This operation though meant that the mortar had a minimum range it could deliver fire to.  The mortar could not be fired safely at any angle less than 40 degrees and even with the smallest propellant charge the bomb would still fall some 100 metres from the firing position.  If the enemy had moved into this dead zone they could not be engaged.  Partially as a solution to this problem, and also to increase firepower, light mortars saw extensive use during World War Two.  These weapons were simply a scaled down version of the mediums.  In many designs the bipod was deleted, the barrel simply being held by the gunner.  Often, the firing procedure was altered in that the bomb was not launched upon hitting the base of the barrel.  Instead, a trigger was fitted which meant the firing pin would not strike the charge until pulled.  There was no facility to alter the propellant charge amount, all ranging being affected by the angle used.

The medium (80 mm calibre) mortar was the first step in the long chain of fire support available to the infantry, which culminated in the massive artillery pieces held under Corps and Army Group control.  It was also one of the most effective.  Firstly, it was integral to the Infantry Battalion, and was not subject to providing other support missions.  Secondly, the steep angle of fire meant a steep angle of descent.  Simply put, the bomb falls very close to the vertical.  This has a profound effect on the blast radius of the bomb on detonation.  Shells fired from artillery pieces had a tendency to 'dig in' on landing, directing a good portion of their explosion into solid ground.  Mortar bombs fell almost on their nose, meaning the bulk of their destructive power was radiated outwards.  Thirdly, the rate of fire they could achieve was astonishing.  An average crew could put a dozen bombs in the air inside of a minute.  Multiply that by six crews in a typical Battalion, and you have over seventy rounds of ammunition impacting on the same target area in sixty seconds.  The effect is too awful to contemplate on men caught in open ground.  Against a machine gun just lying flat provided some defence, but against mortar bombs the only chance was to dig in, deep.  Even then, that high angle could deliver a round right into a dugout.  A well drilled crew could fire around 30 bombs in a minute, though due to the barrel overheating this rate of fire could not be sustained for long.

The success of a mortar strike would bring almost instant retaliation.  Once a firing position was located it could be targeted for 'counter battery fire'.  Here again the mortar had an advantage.  It could be broken down into its three parts and spirited away by Jeep, cart, horse or man in seconds.  Depending on the range, as the first bomb in a series landed, the last one may just have been fired.  That meant the crew could have disassembled their weapon shortly after the last round hit and be gone.  Not a feat that could be achieved with traditional towed artillery.  Light mortars though proved of less use.  Their range, accuracy, rate of fire and destructive impact were all far lower than their medium contemporaries.  Both the Germans and Russians gradually phased theirs out of use, but they never completely vanished.  

Below are detailed the main types of mortars found within the Battalions discussed elsewhere on this site.

British Army

2 inch Mortar

A 2 inch mortar team of 159th Infantry Brigade, 11th Armoured Division, demonstrating the typical manner in which the weapon was deployed

3 inch Mortar

This shot of a 3 in mortar team in North Africa shows some of the paraphernalia needed to keep the weapon in action

The 2 inch mortar was originally issued one per Rifle Platoon, though as the war progressed this extended to one per Carrier Section and each 6 pdr AT Gun crew.  The usefulness of the weapon lay less in its minimal high explosive capability and more in its other munitions.  The suggested load for a Rifle Platoon was 12 rounds HE as opposed to 18 rounds smoke.  The illumination rounds were particularly useful for crew served weapons in lighting up targets.

The specifications for the weapon are difficult to be sure of, as it seems there were over a dozen versions.  These included a Carrier weapon which could be fired from the vehicle and included a larger baseplate.  There was also an airborne model which is quoted at just 4 kg and dispensed with the baseplate in favour of a simple spade.  Perhaps the single greatest advantage the 2 inch had over other such weapons was that, thanks to its trigger operation, it could be fired horizontally against point targets such as bunkers.  This was a dangerous practice, seemingly pioneered by the Commandos, but proved particularly effective in street fighting.  

The 3 inch mortar was a standard medium design.  It was originally dogged by its notably short range.  The early rounds could reach just over 1400 metres, improvements increasing this to 2500 metres.  In the interim some captured German or Italian tubes were used in North Africa to alleviate the problem.  The standard transport for the weapon and crew was the Universal Carrier, fitted for 3-inch mortar.  The weapon had to be dismounted and assembled for firing.  In Airborne units or difficult terrain man or horse power was substituted as appropriate.

The United States Army

60 mm Mortar M2

An indication of the men needed to keep a weapon like the 60 mm in the field.  Note the man second from right bedding the bipod legs in (apologies for the grainy image)

81 mm Mortar M1

The 81 mm mortar, displaying the barrel, bipod and baseplate arrangement which holds good for every medium calibre weapon described here

The 60 mm mortar was one of the more useful light mortars to see service.  It was a normal 'drop fired' weapon issued on the scale of one per Rifle Platoon; in Infantry and Marine Companies they were grouped into a single section, while Airborne, Armored and Ranger units deployed them within the individual Platoons.  If it had one drawback it was the weight, which normally meant a five or six man Squad was required to carry weapon, mount and ammunition.  A cut down model, with no bipod and a spade plate saw some Airborne service.  The M19 weighed over 9 kg, but was not as successful as the standard model.

The 81 mm mortar was another typical medium design, with a particularly good range of almost two miles.  In Infantry Battalions transport was provided by a Jeep and trailer, while Airborne and Marine units used a small, two wheeled hand pulled cart.  The Armored Infantry mounted their mortars on M3 halftracks, designated the M21, the weapon being fired from the carrier without the need for ground assembly.

The Red Army

50 mm Mortar (50-PM 40)

This team are firing the lightweight 50 mm mortar, in which the bipod was deleted, accounting for the serious look on the face of the gunner as he braces the tube for firing.  The small size of the bomb is clearly evident

82 mm Mortar (82-PM 41)

82 mm mortar crews in action.  The men in the right corner are towing the M1910 heavy machine gun

The 50 mm mortar flitted in and out of Red Army service throughout the war.  It was originally intended as a Rifle Platoon weapon, but was soon removed to the Regimental Mortar Battalions.  When these curious short-lived units were disbanded the 50 mm was returned to the Rifle Company in a separate 'Platoon' serving an ever decreasing number of weapons.  The 50 mm served through the war, but its bomb was just too small for the developing artillery dominated doctrine of the Red Army and was often discarded by Battalions.  A lightened version, devoid of the bipod, was also introduced, probably weighing in around 5 to 6 kg.

The 82 mm mortar was another standard weapon, with the best range of the class.  The specifications given above are for the 1941 model, which used pre-fabricated parts to speed production.  I assume this contributed to the notably lighter weight given, as the original PM-37 weighed in at 56 kg complete.  If anyone reading this can shed any light, or knows the breakdown of the component weights, please drop me a line on the address below.  Horse and cart was the prime mover for the mortar, with lorries in motorised units.

The German Army

5 cm mortar (leichte Granatwerfer 36)

A 5 cm grenade launcher crew, almost certainly on the firing range.  The weapon is poised at a particularly steep angle, indicating a short range shot

8 cm mortar (schwere Granatwerfer 34)

Superb study of a mortar in action, capturing the bomb as it slides down the barrel.  The smile on the face of the middle paratrooper suggesting perhaps this was not taken during combat?

12 cm mortar (schwere Granatwerfer 42)

This could be either the Russian original or German copy of the 120mm/12 cm mortar.  Both used the same design and carriage.  To fire, the frame would be removed and the mortar bedded in as usual.  It could not be dismantled as a medium calibre weapon could

The German 5 cm 'light grenade launcher' was issued one per Rifle Platoon at the outset of the war.  It was a heavy, trigger fired weapon with relatively short range and its explosive effect fell far short of the soldiers' requirements.  It saw service in 1939 and 1940, but by 1941 was falling from favour and was gradually withdrawn from frontline units.  It was restricted to high explosive rounds, fifty of which were carried between the three man crew and the Platoon supply wagon.  

The 8 cm 'heavy grenade launcher' was another matter entirely.  There was nothing unique in its design, it was just another standard mortar.  It actually had the shortest range in its class when the British 3 inch mortar was upgraded.  Yet it was the single most lethal weapon at the disposal of the German Infantry Battalion commander.  German mortar crews seemed to gain almost mythic status among friend and foe alike for their effectiveness.  There is no doubting their accuracy, the carnage wrought on so many allied soldiers proved that.  Perhaps their reputation was boosted though by the fact they had more opportunity to engage targets.  There is no suggestion British and American crews were somehow inferior, but by mid-war the Germans were on the defensive everywhere.  That meant they were static while their opponents were advancing to contact, exposed to enemy fire.  German mortar crews had ample experience to perfect their lethal trade.

A shortened, lightened weapon, the Kurzer 42, appeared mid-war.  It weighed around 28 kg complete and had a reduced range of some 1100 metres.  Perhaps this is the weapon which was issued to Rifle Companies in around 1943 in lieu of the 5 cm launcher, as discussed on The German Grenadier Battalion 1943 to 1945 page? 

The 8 cm was carried by horse and cart in Infantry units, lorries and field cars in motorised formations.  Mechanised Panzer Grenadiers deployed the 8 cm mounted in both light and medium halftracks, as the Sonderkraftfahrzeug 250/8 and 251/2 respectively.  In both vehicles the mortar could be fired from the vehicle giving it great flexibility.  

The 12 cm mortar blurred the distinction between infantry weapons and light artillery pieces.  The German Army first encountered this monster the hard way.  The Red Army had introduced the 120 mm HM-38 before the war, and the Germans had a taste of its effectiveness early on.  The weapon was excellent enough to eliminate the usual need to produce a 'Germanic' design and so it was simply copied.  The specifications above should hold good for both Russian and German models and in usual fashion many captured examples were used in Wehrmacht service.  

The Red Army did not include their 120 mm in any Infantry Battalion tables as I recall, but the Germans did their 12 cm copy.  How many units actually received them is highly debateable , but it seems they began to appear at the start of 1944.  The increase in range and firepower was massive but came at some cost.  Firstly, the average rate of fire was halved to six rounds per minute, but this was offset by the tremendous explosive effect.  Of more importance to the German Army was the need to supply each mortar with motor transport.  The 12 cm Platoon represented the largest concentration of vehicles in any Infantry Battalion and due to the weight involved and the need to move the weapons as quickly as possible horse power could not be substituted.  The Raupenschlepper Ost, a tracked lorry, was the preferred tow, though ordinary lorries would suffice.  Panzer Grenadier employed halftracks in the role where available.

7.5 cm le IG 18 (leichte Infantriegeschutz)

The 7.5 cm light gun in action.  It seems a very expensive way to deliver a relatively small round, but the gun remained in service throughout the war

The 7.5 cm light gun was one of many such weapons deployed at Regimental level to give some form of organic artillery support.  As such, they were manned by Infantrymen, not Gunners.  In the German Army, these weapons were also to be found issued directly to Battalions, initially those without Regimental Gun Companies (Panzer Grenadiers, Mountain Troops), latterly Volks Grenadiers and some Grenadier units.

The guns required a great deal of manpower and transport to maintain in action.  Infantry units, as always, relied on horses, roughly a dozen being needed for each gun and ammunition limber.  In motorised units a variety of wheeled and halftrack tows were employed.  In mechanised units, the 7.5 cm was mounted on both light and medium armoured halftracks, as the SdKfz 250/8 and SdKfz 251/9 respectively.  

The guns were far less mobile than mortars, but had the ability to engage both direct and indirect targets, firing either on line of sight or on a steep trajectory.  That flexibility was perhaps the reason they endured in German service throughout the war, despite their obvious limitations regarding mobility. 

The Japanese Army

Type 89 50 mm Mortar (Grenade discharger)

An artist's depiction of the trigger fired 50 mm mortar.  Contemporary American accounts described the weapon as being fired with the base plate braced against the leg.  Ouch... (try www.peleliu.net/JapWeapons/Kmortar.htm for a better illustration)

The Type 89 cannot properly be described as a mortar, as in the truest sense it was nothing more than a grenade launcher.  However, the rounds it fired were not the same as those thrown by the infantryman.

The Type 89 was widely used down to Platoon level where an entire Squad served usually three such dischargers.  Its weight meant it was usually carried against one leg or the other.  This is credited as the reason why the Americans mistranslated the term 'leg mortar' to mean 'knee mortar'.  This was taken to be a reference to the firing procedure, not the carrying method.  Trying to fire the discharger braced against the leg, or any other limb, resulted in a broken bone from the fierce recoil generated.

The long range and lightweight of the discharger, combined with its issue at practically the rate of one per Rifle Squad made it a useful local support weapon.

Type 92 (Battalion Gun)

Fuzzy shot of Japanese troops hauling the small 70 mm gun into action.  The need to transport equipment by hand was due to the lack of motorisation and hostile terrain

The Type 92 was issued at the usual rate of two per Infantry Battalion, though this could be doubled for specific units.

It was a much lighter weapon by comparison to the German 7.5 cm gun, important as it was manhandled or towed by horses wherever the Japanese Army fought.  It benefited from a relatively long range, though it was also deployed at much closer ranges.  By firing at a higher elevation, it was possible to engage targets just 100 metres distant.  This also meant the shells impacted at a much steeper angle, more akin to a mortar than a gun.  Manpower wise it was a very expensive weapon to maintain in the field, but its flexibility more than compensated. 

The Italian Army

45/5 Modello 35

Necessity again forces me to purloin an artist's image.  The 45/5 was a most curious weapon, even down to the cushion depicted above which served as a seat during firing, and helped prevent the heavy tripod hurting the back during carrying.  As much consideration was not given to the weapon's performance

The 'Brixia' was undoubtedly the oddest variant of the mortar ever conceived.  It formed a large part of the firepower of an Italian Infantry Battalion, and as such severely limited their flexibility.

The shortcomings of the 45/5 are endless.  It weighed half as much again as the British 2 inch, yet delivered a smaller round.  The bomb and propellant were actually separated.  The upright magazine held ten charges, one being loaded after the rear mounted breach had been closed following the insertion of a new bomb.  

All in all, the 45/5 was a wholly inadequate support weapon.  But with their 81 mm mortars retained under Regimental control, it was likely to be all a typical Rifle Company could call upon without pressing into service other allied or axis weapons.  It use was sufficiently widespread in North Africa for a German language manual to be produced.  The DAK must have been mightily impressed by the design... 

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