Sticky bomb

The Grenade, Hand, Anti-Tank No. 74, commonly known as the S.T. Grenade or sticky bomb, was a British hand grenade designed and produced during the Second World War. The grenade was one of a number of anti-tank weapons developed for use by the British Army and Home Guard as an ad hoc solution to a lack of sufficient anti-tank guns in the aftermath of the Dunkirk evacuation. Designed by a team from MIR(c) including Major Millis Jefferis and Stuart Macrae, the grenade consisted of a glass sphere containing nitroglycerin covered in a powerful adhesive, and surrounded by a sheet-metal casing. When the user pulled a pin on the handle of the grenade, the casing would fall away and expose the sphere; another pin would activate the firing mechanism, and the user would then attempt to attach the grenade to an enemy tank or other vehicle with sufficient force to break the sphere. After it was attached, releasing the lever on the handle would activate a five-second fuse, which would then detonate the nitroglycerin.

The grenade had several faults with its design. In tests, it failed to adhere to dusty or muddy tanks and, if the user was not careful after freeing the grenade from its casing, it could easily stick to his uniform. The Ordnance Board of the War Department did not approve the grenade for use by the British Army, but personal intervention by the Prime Minister, Winston Churchill, led to the grenade going into production. Between 1940 and 1943, approximately 2.5 million were produced. It was primarily issued to the Home Guard, but was also used by British and Commonwealth forces in North Africa, accounting for six German tanks; used by Allied Forces on the Anzio Beachhead, including the First Special Service Force; as well as by Australian Army units during the New Guinea campaign. The French Resistance were also issued a quantity of the grenades.

Development
Since at least 1938, Jefferis had been toying with the idea of a demolition or anti-tank weapon that would be ideal for irregular warfare. It would work by having an explosive charge deform so that it has a substantial area of intimate contact with the surface of the target. Then, when detonated, the effect of the explosion would be focused on a small area and would rupture an armoured plate much thicker than would otherwise be the case. Sappers call such a device a "poultice" or "squash head" charge. Jefferis enlisted Drs Bauer and Schulman of the Colloid Science Department of Cambridge University, they had experimented with lengths of bicycle inner tube filled with plasticine to represent the explosive. These were fitted with wooden handles and dipped in rubber solution to make them sticky. In experiments, these prototypes proved difficult to aim and only by chance did any stick to the metal bins used to represent tanks.

With the end of the Battle of France and the evacuation of the British Expeditionary Force from the port of Dunkirk between 26 May and 4 June 1940, a German invasion of Great Britain seemed likely. However, the British Army was not well equipped to defend the country in such an event; in the weeks after the Dunkirk evacuation it could only field twenty-seven divisions. The Army was particularly short of anti-tank guns, 840 of which had been left behind in France and only 167 were available in Britain; ammunition was so scarce for the remaining guns that regulations forbade even a single round being used for training purposes.

Under the circumstances, Jefferis considered that his idea might have more general application for the British Army and the Home Guard. Jefferis was in charge of a department known as MIR(c), which had been created to develop and deliver weapons for use by guerilla and resistance groups in Occupied Europe. MIR(c) was now charged with the development of the Sticky Bomb.

The problem of designing a sticky bomb had been delegated to the enthusiastic genius of Robert Stuart Macrae. Clearly, some sort of flexible bag was required to contain an explosive gel so that it did not matter how the bomb landed on the target. However, a flexible bag is hard to throw and trials had not been at all satisfactory.

Discussions of the problem in Macrae's office were overheard by Gordon Norwood, a master printer who Macrae had recruited from his former magazine publishing employer, but he was not directly working on the weapon. Norwood suggested that what was needed was a frangible container and to the annoyance of the War Office store keeper he obtained a 150 W light bulb with which to demonstrate his point: a spherical glass flask inside a sock of woven wool is rigid when thrown, but on contact the glass breaks and the bomb deforms to the required shape. Experiments with glass flasks filled with cold porridge confirmed that this was the way to go. The grenade needed a delay for the thrower to get clear, so the woollen sock was covered in a sticky substance ensuring that the bomb stayed in place for a few seconds before detonating. Having covered the bomb in glue, a non-sticky handle was required; in the handle, a delay fuse ignited by releasing a sprung lever so that a five second time delay starts as the grenade leaves the thrower's hand (just like the levers found on a conventional Mills bomb type hand grenade).

Meanwhile, finding a suitable adhesive was a significant problem. After unsuccessful experiments with a variety of candidates, somebody suggested birdlime – a viscous sticky compound used since ancient times to trap birds by spreading it on tree branches and waiting for birds to get stuck. Birdlime performed better than anything previously tested, but it was still not good enough. Macrae's tin of birdlime was labelled with a large letter 'K' and an indication that tin came from Stockport but with no more clues as the manufacturer. Macrae got on a train to Stockport and there found a helpful taxi driver who took him to Kay Brothers Ltd. The company's Chief Chemist was soon working on the problem of a suitable adhesive and within a matter of weeks the problem was solved to Macrae's satisfaction.

The filling for the bomb was developed by ICI. It was nitroglycerin-based with a variety of additives to make it more stable and viscous. The glass flask containing the main charge held about 1+1/2 lb of this explosive that was described as having the consistency of Vaseline.

The adhesive surface was protected by a light metal case which was released by pulling a safety pin: the case fell away as two hemispheres connected by a sprung hinge. The inside of the case was fitted with a number of rubber spikes that kept it clear of the glued surface of the grenade. Early models also had a strip of adhesive tape round the neck of the casing.

Development continued, but there were problems with service regulations that were not written with such an unconventional weapon in mind. The sticky bomb was inevitably rather fragile and even a specially designed box could not fully meet the army's demanding requirements for withstanding rough handling without damage. It seemed there were problems at every turn. The Prime Minister, Winston Churchill, who was concerned with the state of the country's anti-tank defences, learnt about the grenade and urged its development. The Ordnance Board of the War Office did not approve the grenade to be used by the Army. However, Churchill ordered further tests to be conducted in July, and after personally viewing a demonstration of the grenade ordered that it immediately be put into production. His memo of October 1940 simply read "Sticky bomb. Make one million". A couple of days later, Anthony Eden, then Secretary of State for War, added a scribbled note to a cabinet minute that recorded the order to go ahead with the bomb:

"Anti-Tank (& indeed anti-enemy generally) bombs for Home Defence are vitally urgent and should be available in very large quantities. I don't mind where they come from as long as we get them, home or abroad. [emphasis as in original]"

In spite of top level pressure, the arguments rumbled on. Trials were disappointing, it was not possible to get the bomb to adhere to any surface that was wet or covered with even the thinnest film of dried mud "a customary condition of tanks" as Major-General Ismay, on 27 June, could not resist pointing out.

Churchill was not amused:

"General Ismay, I understand that the trials were not entirely successful and the bomb failed to stick on tanks which were covered in dust and mud. No doubt some more sticky mixture can be devised and Major Jefferis should persevere. Any chortling by officials who have been slothful in pushing this bomb, over the fact that at present it has not succeeded will be viewed with great disfavour by me."

Macrae, Ismay and Churchill all saw fit to record these arguments over the technical issue of stickiness. As Eden had pointed out, there was a lot at stake. The British infantry and Home Guard had little with which to put up a fight against tanks and to any who had witnessed trials of Molotov Cocktails and SIP grenades it was evident that they could do little to a modern tank other than to provide a blinding pall of smoke. What was needed was a hand weapon to deliver a coup de grâce by punching through the armoured plate. The sticky bomb could do the job and little else was available.

In his memoirs, Ismay recalled that he never solved the puzzle of how to convey his very genuine concerns of the time to the right people. A thrown sticky bomb simply would not reliably stick to a vertical surface. However, the bomb would stick if it was thrown onto the top of a tank where the plates were more or less horizontal – and thinner – but this reduced the throwing range to twenty yards at the most – getting that close would only be possible in an ambush or in street fighting.

Churchill considered any obstruction, however well-meaning, as singularly lacking in imagination. In the event of invasion, he foresaw a desperate fight to the last and after the war, he wrote about how he envisaged the use of the sticky bomb: "We had the picture in mind that devoted soldiers or civilians would run close up to the tank and even thrust the bomb upon it, though its explosion cost them their lives. There were undoubtedly many who would have done it [Italics added for emphasis]." He also later recorded how he intended to use the slogan: "You can always take one with you."

Arguments rumbled on and there were endless delays. Early versions of the sticky bomb were prone to leaks as well as breakage in transport. There were understandable concerns over the explosive charge: pure nitroglycerin is notoriously susceptible to the slightest knock, but the mixture developed by ICI proved to be very safe even if it should get into the hinges of the storage boxes. By December 1940, fewer than 66,000 had been produced and the rate of production was disappointing at five to ten thousand per week. Further, it was suggested that the original order of one million be reduced to 200,000. Minor improvements to the design were made, of which the most significant was to replace the glass flask with plastic. Finally, after passing all the required tests, the sticky bomb – now the No 74 Grenade Mk II – was accepted by the Ordnance Board; it was put into full-scale production and it became a service issue.

On 14 May 1941, Lieutenant-General Sir Ian Jacob reflected:

"The most extraordinary feature of the whole business, however, was the fact that the Secretary of State for War, in a Minute addressed to the Prime Minister on 25 November, 1940, said that the Director of Artillery and the Ordnance Board had only just been able to obtain from ICI the details of the explosive contained in the bomb. Seeing that the bomb was demonstrated in June 1940, this statement can hardly hold water. The War Office seems to be to blame in that, up to the end of April, 1941, no sticky bombs had been issued to any unit, nor had any dummies been provided for training. In view of our acute shortage of anti-tank weapons, the whole story is discreditable."

Between 1940 and 1943 approximately 2.5 million were produced.

Design
The Grenade, Hand, Anti-Tank No. 74 consisted of a glass sphere in which was contained approximately 1.25 lb of semi-liquid nitroglycerin devised by ICI. The sphere was covered in stockinette which was coated with a liberal amount of birdlime, an extremely adhesive substance from which the nickname 'sticky bomb' was derived. A casing made out of thin sheet-metal, and formed of two halves, was then placed around the sphere and held in place by a wooden handle, inside which was a five-second fuse. The handle also contained two pins and a lever; the first pin was pulled out to make the casing fall away, and the second to activate the firing mechanism in the grenade. This primed the grenade, with the lever being held down to ensure the fuse was not triggered; then the user would run up to the tank and stick the grenade to its hull, using as much force as possible to break the sphere and spread the nitroglycerin onto the hull in a thick paste. Another alternative was for the user to throw it at the tank from a distance. Either way, the lever would be released and the fuse activated, and the grenade would then detonate.

The grenade did possess several problems with its design. Users were urged to actually run up to the tank and place it by hand, rather than throw it, thus the adhesive could very easily stick to their uniform in the process; the user would then be placed in the unenviable situation of attempting to pry the grenade loose whilst still holding onto the lever. It was also discovered that as time passed the nitroglycerin began to deteriorate and become unstable, which made it even more difficult to use. As the grenade was a short-range weapon, users were trained to hide in a trench or other place of concealment until the tank went past them, and then to stick the grenade to the rear of the tank, where its armour was thinnest. However, provided that they were not in line with the handle when it detonated they were relatively safe if only a few yards away. The Mark II design used a plastic casing instead of glass, and a detonator instead of a cap.

Operational use


According to a War Office training pamphlet dated 29 August 1940, the sticky bomb should be regarded as a portable demolition device which can be "quickly and easily applied". It was reckoned to be effective against armour of up to one inch (25 mm) thickness and was suitable for use against "baby" tanks, armoured cars and the vulnerable points on medium and heavy tanks. The safest and easiest application was simply to drop it from an upstairs window; otherwise, it could be used in an ambush of mobile tanks moving along a narrow road or in an attack on tanks parked up for the night. The sticky bomb could be either thrown or slapped in place by hand, in the latter case, the advice was to use sufficient force to break the glass thereby creating a greater area of contact resulting in a more effective explosion. Finally, there was also the option of placing the bomb first and then pulling out the pin at a safe distance by means of a length of string.

Macrae credits the Australian army with developing the technique of slapping a sticky bomb directly onto a tank instead of throwing it from a relatively safe distance. Since the bomb used a blast effect, it was safe to do this and walk away provided only that the bomb's handle was pointing away from the bomber – the handle would be shot away from the explosion "like a bullet." Macrae gives no date for the development of this tactic. Macrae confirmed that placing the bomb rather than throwing it gives better adhesion and allows thicker plates to be penetrated.

The potential of the sticky bomb for physical humour has frequently proved too tempting to be neglected, a good example being David Niven's novel Go Slowly, Come Back Quickly. The unfortunate officer Stanni, while attempting to demolish a smelly privy, loses his dignity and a large section of trouser fabric to such an incident. The sticky bomb also featured in the British television comedy series Dad's Army. In the episode Fallen Idol Lance-Corporal Jack Jones sticks his grenade to an improvised target and retires as instructed but keeps a hold of the grenade which is now primed and stuck to an old dustbin lid.

However, the dangers inherent in the weapon were real enough, if the bomb became inadvertently stuck in mid-throw, it could easily be pulled from a soldier's hand triggering the firing mechanism and putting him in mortal danger. There were tragic accidents during training.

By July 1941, 215,000 sticky bombs had been produced. Of these, nearly 90,000 had been sent abroad to North and South Africa, the Middle East and to Greece where it did useful service. The remainder were stored at Ordnance Depots or distributed to army and Home Guard units. There were many calls for the total production to be cut back and it is not clear how many were manufactured by the end of the war, but it was probably not much more than 250,000.

The grenade was first issued in 1940 to Home Guard units, who appeared to have taken a liking to it despite its flaws. Although the Ordnance Board had not approved the grenade to be used by Regular Army units, a quantity were provided for training purposes. However, a number of sticky bombs did find their way to British and Commonwealth units participating in the campaign in North Africa, and were used as anti-tank weapons. During the Afrika Korps advance towards the town of Thala in February 1943, they accounted for six German tanks. They were also issued to units of the Australian Army, who used them during the Battle of Wau and the Battle of Milne Bay. They were used by various allied units on the Anzio Beachhead, namely the First Special Service Force, who obtained them from the British. A large number were also supplied to the French Resistance.

Recognition
In 1947, the Royal Commission on Awards to Inventors considered claims from Macrae and from the managing director of Kay Brothers. Macrae's legal representative was Edward Terrell – himself a wartime inventor. At the time the crown opposed granting an award; when Macrae was asked what elements of the sticky bomb he claimed to have invented, he replied "I am claiming no invention; I merely claim the development of the bomb, which was my job." However, in 1951, the commission recommended that Macrae should receive an ex-gratia payment of £500 [about £0 in ] and Norwood received £250 [£0] for his contribution.

Users
Users of the grenade included:
 * 🇦🇺 Australia
 * Free French Forces
 * 🇬🇧 United Kingdom