In the desperate summer of 1940, after the fall of France and the miraculous evacuation at Dunkirk, the British military faced the prospect of imminent German invasion with severely depleted conventional forces. The Home Guard, a militia force of older men and those unfit for regular military service, would form the last line of defense against any German landing. Recognizing that conventional anti-tank weapons would be insufficient, Winston Churchill approved emergency development and production of an unconventional anti-tank weapon designed specifically for use by poorly trained, hastily organized civilian soldiers: the No. 74 Anti-Tank (AT) Grenade, colloquially known as the "Sticky Bomb."

The weapon was developed by Stuart Macrae and Cecil Vandepeer Clarke, British military inventors working in 1940. The design was conceptually straightforward: a glass sphere approximately the size of a grapefruit, filled with a nitroglycerin-based adhesive paste, covered in a sock or cloth bag soaked in the same adhesive to improve its grip on steel surfaces. The armed grenade was to be thrown or pushed against the side of a tank, where the adhesive would cause it to stick to the armor plating. Once attached, a time fuse of approximately four and a half seconds would detonate the charge, theoretically blowing a hole in the tank's hull through which shrapnel would penetrate the interior. The whole device weighed approximately 2.5 pounds.

The weapon system's fundamental flaw was in its adhesive layer. The nitroglycerin-based sticky paste was designed to adhere to steel tank armor, but it equally adhesive to human skin and clothing. Troops using the weapon frequently found the device sticking to their hands, fingers, uniforms, and equipment as firmly as it would adhere to a tank's armor. Moreover, the adhesive could be affected by mud, dust, rain, and atmospheric conditions. If a tank had muddy armor or accumulated dust and grime—common conditions in field operations—the adhesive would fail to grip properly and the bomb would simply fall off before detonation.

Another critical vulnerability emerged from the very design of the weapon: a soldier employing a sticky bomb had to approach a tank in operation, get close enough to push the device against its armor, and escape before detonation. This required approaching an armored vehicle defended by machine guns, where all occupants would be aware of the presence of a soldier attempting to place an explosive against the hull. The blast radius of detonation was sufficient to injure or kill the soldier who had placed it if they were not at sufficient distance.

Despite its evident disadvantages, the War Office approved emergency production. Approximately 2.5 million No. 74 AT grenades were manufactured between 1940 and 1943. They were issued primarily to Home Guard units for potential deployment in the event of German invasion. Once it became clear that immediate invasion was no longer a threat—following the German invasion of the Soviet Union in June 1941 and the commitment of German military resources to the Eastern Front—the sticky bomb's primary justification disappeared. Yet production continued, and significant quantities were distributed to combat units in North Africa and Burma as the war progressed.

Combat use of the No. 74 AT grenade was limited and largely unsuccessful in conventional military operations. Regular tank crews trained in anti-tank defense were far too capable at preventing hostile soldiers from approaching close enough to place an anti-tank grenade. The weapon found occasional utility in the hands of partisan forces and resistance fighters in theaters where conventional military organization was absent and unconventional tactics predominated. A few confirmed tank kills were attributed to sticky bomb attacks by partisan forces in North Africa and by British and Commonwealth troops in Burma, but these represented anomalies rather than the norm. The overwhelming majority of the 2.5 million sticky bombs manufactured during the war were never used in combat at all.

Churchill himself addressed the concept in his memoir The Gathering Storm, published in 1948, defending his decision to approve emergency production of unconventional weapons in 1940 as a necessary response to existential threat: if invasion had occurred, any anti-tank capability, however flawed, would have been better than none. His logic reflected the desperation of the moment—with regular military supplies depleted and German invasion seemingly imminent, approving production of an imperfect weapon was preferable to having no defensive capability at all.

The No. 74 AT grenade exemplifies a particular category of weapons failure: the emergency improvisation. Unlike Project Habakkuk or the Panjandrum, which were carefully designed by military engineers over extended development timelines, the sticky bomb was essentially a rapid prototyping solution to an immediate crisis. The adhesive chemistry was imperfectly understood, the design had not been thoroughly tested under field conditions, and the fundamental tactical assumptions underlying its employment were questionable. Yet it was produced in enormous quantities precisely because conventional supply chains were broken and improvisation was the only option available.

The sticky bomb's ultimate fate was irrelevance through circumstance change rather than technological obsolescence. The German invasion never occurred. The Home Guard was never deployed in combat in its intended defensive role. The sticky bombs, meant to be the last-ditch weapons of an invaded Britain, became historical curiosities—weapons manufactured by the millions that were never fired in anger, stored in warehouses and magazines until they were eventually disposed of as dangerous waste. In this sense, the No. 74 AT grenade succeeded by failing: because it was produced in such enormous quantities and available as a last resort, the desperate scenario that would have required its employment never came to pass.