The term “blockbuster” is widely popular in cinematography today, signifying something immensely popular and groundbreaking. However, this term originated during World War II, coined by British journalists, and unofficially designated the heavy bombs used by British aviation. This name, “block destroyers,” perfectly characterized the purpose of these heavy bombs, available in 4, 8, and 12-thousand-pound calibers.
The directive for designing high-power heavy bombs was issued in September 1940, outlining specific requirements. Significant debate ensued regarding the choice of explosive; amatol was preferred, but concerns arose about its availability in sufficient quantities. Consequently, a mixture of RDX and TNT was chosen, as Britain possessed ample stocks of these. Ultimately, however, serial bombs were equipped with pure amatol.
Design and Development
The primary challenge was fitting the bomb into the bomb bay of the “Wellington” bomber. Barnes Wallis, working at Vickers Armstrong Ltd, ingeniously resolved this task in just six weeks by October 1940. Dr. Alfred Brooks oversaw the overall project, later receiving the Order of the British Empire in 1947 for his creation of the “Blockbusters.” The bomb itself was often referred to in the English press as “Blockbuster Brooks.”
Initially, four fuzes were placed on the bomb, providing four activation modes: half-second instantaneous, 30-second delay, 30-minute delay, and “long” delay. These multiple fuzes were later removed from serial production due to the specific nature of deploying the bombs against cities.
The 4000-pound bomb, a simple cylinder, entered testing in the autumn of 1940. It featured a relatively thin-walled casing and a large explosive content, which comprised three-quarters of the bomb’s total mass (1360 kg). Contrary to initial forecasts regarding the explosive type, serial bombs were equipped with pure amatol.
Experiments were conducted during 1940 to equip the bomb with a ballistic nose cone, a tail section with annular stabilizers, and a parachute system. Drop tests with such parachute-equipped bombs were carried out at Vickers Armstrong in December 1940 but were never completed. The ballistic tip and stabilizer showed no significant advantage over the standard “barrel-shaped” form, as the bomb still oscillated in flight. Therefore, these additional “devices” were abandoned, and serial bombs were typically used without them. The blunt-nosed shape ensured an explosion on the surface without deep ground penetration, directing the blast wave almost parallel to the ground and causing immense damage to structures.
Deployment and Variants
By the end of February 1941, an order for the first thousand serial 4000-pound “Cookie” bombs was placed, followed by an ongoing order for 360 bombs per month. Their active deployment began in May 1941, with 226 bombs of this type dropped by August 1941. In January 1942, the bomb was officially adopted by the RAF as the “4000lb HC Mk.I.”
Several modifications were released later. The Mk.II featured three fuzes instead of one, concentrically arranged in the nose at a slight angle to the longitudinal axis. In the Mk.III, two more fuzes were added to the bomb’s side surfaces. The Mk.IV introduced a device for suspending and hoisting the bomb onto the bomber.
During a visit to England, American General Arnold was highly impressed by the “Cookie” bomb, noting that the maximum caliber bomb in American aviation was 2,000 pounds. Upon returning to the USA, General Arnold requested the Ordnance Department to develop a similar bomb. The British later provided their transatlantic allies with all documentation for the “Cookie” bomb. A similar munition was then mass-produced in the USA under the designations “4000lb HC Mk.V” and Mk.VI.
Legacy and Effectiveness
Between 1941 and 1945, approximately 93,000 “Cookie” bombs were produced. Their deployment demonstrated that the 4000-pound Blockbuster was 1.4 times more effective against urban areas than an equivalent total weight of general-purpose bombs. This was unsurprising, given that a single “Cookie” contained 2.5 times more explosive content than general purpose bombs of similar weight.