Sticky bomb

In 1938, Maj. Millis Jefferis developed the idea of a anti-tank weapon that would be ideal for irregular warfare. It would have an explosive charge deform so that it had a substantial area of intimate contact with the surface of the target.[4] Then, when detonated, the effect of the explosion would be focused on a small area and would rupture an armored plate.[4] Sappers call such a device a "poultice" or "squash head" charge.[4] Jefferis enlisted Bauer and Schulman of the Colloid Science Department of Cambridge University, they 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 stuck to the metal bins used to represent tanks.[5]

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.[6] 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.[7] 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.[7]

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 guerrilla and resistance groups in occupied Europe.[8] MIR(c) was now charged with the development of the sticky bomb. The problem of designing a sticky bomb was delegated to Robert Stuart Macrae.[5]

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 was found to be 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. He obtained a 150 W light bulb with which to demonstrate his point: a spherical glass flask inside a sock of woven wool, rigid when thrown, but on contact the glass broke and the bomb deformed to the required shape.[9] Experiments with glass flasks filled with cold porridge confirmed that this was the way to go.[10]

The grenade needed a delay for the thrower to get clear, so the woolen sock was covered in a sticky substance ensuring that the bomb stayed in place for a few seconds before detonating.[10] Having covered the bomb in glue, a non-sticky handle was required. In the handle, a delay fuse was ignited by releasing a sprung lever so that a five second time delay started as the grenade left the thrower's hand (just like the levers found on a conventional Mills bomb type hand grenade).[11]

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 to the manufacturer. Macrae got on a train to Stockport and there found a taxi driver who took him to Kay Brothers Ltd.[11] 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.[12]

The filling for the bomb was developed by ICI.[11] 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 (0.68 kg) of this explosive that was described as having the consistency of Vaseline.[13]

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.[11] Early models also had a strip of adhesive tape round the neck of the casing.[13]

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.[14] 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.[15]

The Ordnance Board of the War Office did not approve the grenade to be used by the army.[16] 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.[17] His memo of October 1940 simply read "Sticky bomb. Make one million".[18] 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:

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, pointed out.[19]

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.[20]

Macrae, Ismay and Churchill all saw fit to record these arguments over the technical issue of stickiness.[21] 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.[22] 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.[23]

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.[24] A thrown sticky bomb simply would not reliably stick to a vertical surface; 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 20 yd (18 m) at the most, getting that close would only be possible in an ambush or in street fighting.[25]

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". He also later recorded how he intended to use the slogan "You can always take one with you".[26]

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.[27] By December 1940, fewer than 66,000 had been produced and the rate of production was disappointing at five to ten thousand per week. It was suggested that the original order of one million be reduced to 200,000.[23] 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.[28]

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.[29]

Between 1940 and 1943 approximately 2.5 million were produced.[30]

Sticky bomb diagram. British explosive ordnance[31]

The grenade, hand, anti-tank No. 74 consisted of a glass sphere in which was contained approximately 1.25 lb (0.57 kg) 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 placed around the sphere and held in place by a wooden handle, inside which was a five-second fuse.[32] 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.[16] 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.[33]

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.[16] 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 armor was thinnest.[34] Users were relatively safe from a few yards away, as long as they were not in line with the handle when it detonated.[35] The Mark II design used a plastic casing instead of glass, and a detonator instead of a cap.[36]

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".[13] 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.[13]

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.[13] 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.[13]

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.[35] 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."[35] 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.[28]

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 they did useful service.[39] The remainder were stored at Ordnance Depots or distributed to army and Home Guard units.[39]

The grenade was first issued in 1940 to Home Guard units, who appeared to have taken a liking to it despite its flaws.[40] Although the Ordnance Board had not approved the grenade to be used by regular army units, a quantity were provided for training purposes.[16] 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.[41]

They were also issued to units of the Australian Army, who used them during the Battle of Wau[42] and the Battle of Milne Bay.[43] 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.[44]

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.[45] 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."[46] However, in 1951, the commission recommended that Macrae should receive an ex-gratia payment of £500 (equivalent to £16,700 in 2021) and Norwood received £250 (equivalent to £8,400 in 2021) for his contribution.[45][47][48]

Users of the grenade included:

•  Australia[42]
•  Free French Forces[44]
•  United Kingdom[16]

• British anti-invasion preparations of World War II
• No. 73 grenade
• No. 76 special incendiary grenade
• Blacker Bombard
• Smith Gun
• Northover Projector
• PIAT

Wikimedia Commons has media related to Sticky bomb.

• Home Guard site
• The Home Guard Pocket Manual, by Capt. A. Southworth, M.B.E., pp 47–48: description of the sticky bomb, use and diagram.
• Imperial War Museum Collection Search: sticky bomb (search results)

• H 30178 (photograph): Home Guardsmen training with the sticky bomb

• Manufacturing at Kay Brothers
• School for Home Guard - news item featuring sticky bomb (Newsreel). British Pathé. 7 August 1941. Event occurs at 0:27. Retrieved 8 March 2010.