WWII Tech Pubs Briefing

Written by
The TechPubs Team

Unsupported by armour or anti-tank guns, a company of British infantry holding the line in Calais, France has to rely on a brave sapper to stop the onslaught of German Panzer IIIs. With a great deal of luck, the satchel charge he has thrown will lodge in the lead tank’s running gear and immobilize it in the French cobblestone lane, fouling the advance of the column behind it.

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Overview

Military engineers have been using explosives since the invention of gunpowder, working alongside front-line troops in extremely hazardous conditions. During World War I, to overcome the bloody stalemate of trench warfare, engineers dug tunnels under enemy positions, packed them with explosives, and detonated these “mines” in attempts to breach enemy lines. Although the Battle of the Somme opened with the explosion of two such mines, the most dramatic use occurred at Messines, Belgium, where 19 mines containing 470 long tons (478 tonnes) of explosives were simultaneously detonated, causing 16,000 dead or missing German casualties and demolishing huge sections of German trenches and fortifications.

The more fluid nature of warfare in World War II meant that demolition explosives would play a much smaller role, although German paratroopers used regular explosives and shaped charges to spectacular effect in their assault on the fortress of Eben Emael in Belgium. Here, a small, highly trained unit landed in gliders on the fortress and neutralised the guns guarding a key approach to be used by the German army at the start of the Blitzkrieg in 1940. Demolitions were also used to clear anti-tank obstacles or barbed wire ahead of an assault. In a defensive role, demolitions could be used to destroy bridges or military installations, especially ports, to slow an advancing army.

Much of the skill in using explosives comes from knowing where and how to place them. To destroy hardened structures, a charge has to have its blast directed inwards, towards the structure. If simply placed onto or next to the target, the majority of the explosive force is lost, as it is directed harmlessly away from the target and into the air. Tamping the explosives, typically with sandbags, is the answer to this problem. Heavy sandbags packed around the explosive charge concentrate the force of the explosion toward the target, vastly increasing its destructive potential.

In World War II, satchels were sometimes used to carry or secure explosives. These were normally simply bags with handles, similar to briefcases used to carry documents. These “satchel charges” were made up in relative safety with a pre-determined amount of explosives, then carried to their target, placed carefully, and tamped - often under fire. The engineer could detonate the explosives with a safety fuse, with a flash fuse on a timer, or with an electric charge sent through wires from a plunger or twist generator operated from a safe distance.

The explosive force and weight of a infantry-borne explosive charges can range from 100 g (3.5 oz) to several kilograms of explosive. German troops often used six stick-grenade heads secured around a seventh, which they colloquially called the Geballte Ladung (clenched charge), confusingly the same name officially applied to standard demolitions TNT containers. The seven grenades combined to supply 1.155 kg (2.55 lb) of TNT.

Using a satchel charge against enemy armour was a hit-or-miss affair. The soldier would try to toss the satchel charge onto or under the tank from very close range. In order to be vulnerable to such an attack, the tank would usually have to be slowed or halted or have its maneuverability reduced by obstacles or terrain such as an urban setting. Targeting the engine deck was effective as blast and/or hot gases could enter the engine compartment via cooling grills, where petrol fumes present due to blast-ruptured fuel lines or poor maintenance might ignite. Such a result would most likely destroy the engine and the fire could detonate on-board ammunition and brew up the tank.

Yet, satchel charges proved most effective against tank tracks. Placed in or under the track, they would break the track and probably cause running gear damage. In most cases, these immobilized tanks retained their armament, becoming, in effect, pillboxes.

If a satchel landed anywhere else on the tank, it would have little chance of doing serious damage – perhaps minor fittings, aerials, and the like might be destroyed. With luck, a sub-optimally placed satchel charge might produce spall inside a tank, concuss the crew, or injure someone directly opposite the detonation point. If a charge exploded on top of a hatch, it might blow the hatch open, allowing a soldier to drop a grenade into the tank.

During the Winter War, Finnish General Headquarters studied the effectiveness of its anti-tank kasapanos (piled charge). It noted in February 1940 that 1.0-2.0 kg (2.2-4.4 lb) of TNT was sufficient to sever the track of a tank if blown under or next to the track. A charge of 2.0 kg (4.4 lb) could destroy vehicles of around 6.0 tonnes (5.9 long tons), 3.0 kg (6.6 lb) was sufficient to destroy 12.0-tonne (11.8-long-ton) vehicles, and 4.0 kg (8.8 lb) was sufficient for 30-tonne (29.5-long-ton) vehicles such as the Soviet T-28 medium tank.

According to the Finns, 6.0 kg (13.2 lb) of explosives was powerful enough to knock out any tank of 1940 vintage, provided a soldier could get close enough to place it and placed it where it could do damage, on the tank’s rear deck. Destroying a tank with a satchel charge any other way was extremely difficult, as the charge could not be tamped and so much of the explosive force was lost. Some success was scored by soldiers who lay in trenches and allowed a tank to pass overhead, then secured explosives to the weaker underside armour of the tank with adhesive. When this worked, it would incapacitate the crew with over-pressurisation rather than disable the tank itself.

Despite whatever theoretical effectiveness explosive charges had in stopping armoured vehicles, they had many disadvantages. In general, high explosives were confined to engineering stores. Soldiers had to be trained in their use and bricks of TNT (or the equivalent) were not standard infantry issue. Furthermore, the attacker needed to just about crawl on top or beneath an enemy tank to make an attack. Because of these drawbacks, and limited opportunities, successes against tanks rarely occurred. Until the introduction of infantry anti-tank weapons such as the Panzerfaust (tank fist), PIAT (Projector Infantry Anti Tank), and bazooka, anti-armour defence depended on crewed anti-tank guns. Using a satchel charge to take out a tank was a desperate move forced by the absence of more effective anti-tank weapons.

Satchel charges were not the only improvised anti-tank weapons. Molotov cocktails, which contained petrol, a thickener, and a fuse, and other fire-based weapons could succeed if they set the vehicle’s engine afire or somehow found their way into the fighting compartment. Military Training Pamphlet No. 42: Tank Hunting and Destruction, a British Army publication produced in August 1940, included even more desperate measures. It suggests that a team of four can take out tanks with a length of railway track, a blanket, a bucket of petrol, and matches. The team was to hide in an alleyway or alongside a house where the tank is expected to pass. Two men hold the railway track with the blanket draped over it. As the tank passes the hiding place, these two run out and jam the railway track into the tank’s suspension. The third man throws the bucket of petrol over the blanket, now entangled in the track, and the fourth sets it on fire. Another plan from that booklet is for a single man with a hammer and hand grenade to station himself near the expected route of a tank. When the tank passes, the man is to jump onto the passing tank and pound on the turret hatch with the hammer. When the tank commander opens the hatch to find out what is going on, the attacker is to drop the hand grenade inside. There is no record of these tactics ever being attempted.

At the start of World War II, all countries had standard demolitions explosives. Great Britain used guncotton, which was issued in tin cases containing 14 1.0-lb (0.45-kg) slabs in the explosive’s wet form for demolitions purposes and in boxes of six tin tubes that each contained ten primers in the dry form for detonators, and ammonal, a less violent explosive that was issued in tins of 2.5, 25, and 50 lb (1.1, 11, and 22.7 kg). Germany’s Geballte Ladung, TNT contained in a watertight zinc container, was issued in standard sizes of 1.0, 3.0, and 10.0 kg (2.2 lb. 6.6 lb, and 22.0 lb) although other, smaller 100-g (3.5-oz) and 200-g (7.1 oz) charges existed for specialized work.

As the war progressed, more powerful explosives developed. The Allies developed RDX (Research Department Explosive) which was later used as the base of plastic explosive and which was also used to fill the blockbuster aerial bombs. Germany developed aluminised explosives that greatly increased the temperature of detonation (and thus blast effect) and eliminated the need for an incendiary component in their cannon Minengeschoss (mine projectile), and Nipolit, an explosive of high mechanical strength that could be cut, shaped, or milled like hard plastic.

The Allied Bangalore Torpedo and the German Rohrladung (tubing charge) were small-diameter tubes filled with explosive that were used to clear barbed wire. Several tubes could be clipped together end to end, then pushed under the wire and detonated to clear a path through the wire obstacle.

The Munroe effect of a shaped charge - producing a supersonic blast of gas and molten metal - was well known and employed by all combatants early in the war. Great Britain and France had effective anti-tank rifle grenades in 1940 and German refinements led to the Hafthohlladung (detention hollow charge), a magnetically attached anti-tank weapon that ranged in size from 2-10 kg (4.4-22 lb), in 1942. The Hafthohlladung could also be attached to a concrete blockhouse by a length of chain to blast a hole through the wall. Another version of this was the Abstandsladung (spacer charge) H15, which was fitted with folding legs and was used for attacking armour plate and reinforced concrete in static defences. Great Britain developed three types of shaped charges: the Beehive Charge that was used for burning holes through concrete or armour plate, etc; the Hayrick Charge, a linear charge that was used for cutting the reinforcing bars in concrete, etc; and the arched or General Wade Charge, which was an arched linear charge that would give a combined cutting and pressure effect.

As the war progressed, ranged shaped-charge weapons such as the US bazooka, the British PIAT, and the German Panzerfaust evolved. Germany developed a series of remotely controlled vehicles that could deliver an explosive charge under fire, and the British produced the Gammon grenade, basically a grenade whose explosive filling could be added as and when required, and developed HESH (High Explosive Squash Head) for use against fortifications, although it today serves as the UK’s preferred anti-armour round.

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Specifications

Specifications are for the British satchel charge.

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