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SD 2 – Closed: fuze is not yet armed.
SD 2 – Open: wings have flipped open and screw threads at the base of arming spindle are visible: fuze is now armed.

The Butterfly Bomb (or Sprengbombe Dickwandig 2 kg or SD 2) was a German 2-kilogram (4.4 lb) anti-personnel submunition (or bomblet) used by the Luftwaffe during the Second World War. It was so named because the thin cylindrical metal outer shell which hinged open when the bomblet deployed gave it the superficial appearance of a large butterfly.[1] The design was very distinctive and easy to recognise. SD 2 bomblets were not dropped individually, but were packed into containers holding between 6 and 108 submunitions e.g. the AB 23 SD 2 and AB 250-3 submunition dispensers. The SD 2 submunitions were released after the container was released from the aircraft and had burst open. Because SD 2s were always dropped in groups (never individually) the discovery of one unexploded SD 2 was a reliable indication that others had been dropped nearby. This bomb type was one of the first cluster bombs ever used in combat and it proved to be a highly effective weapon. The bomb containers that carried the SD 2 bomblets and released them in the air were nicknamed the "Devil's Eggs" by Luftwaffe air and ground crew.[2]

Description

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The SD 2 submunition was a 76-millimetre (3.0 in) long cylinder of cast iron, which was slightly larger in diameter before its wings deployed. A steel cable 121 mm (4.8 in) long was attached via a spindle to an aluminium fuze screwed into the fuze pocket in the side of the bomblet. The outer shell was hinged and would flip open as two half-cylinders when it was dropped. Additionally, spring-loaded wings at the ends would flip out. The wings at the end were canted at an angle to the airflow, which turned the spindle (connected to the fuze) counterclockwise as the bomblet fell. After the spindle had revolved approximately 10 times (partially unscrewing itself from the bomb) it released a spring-loaded pin inside the fuze, which fully armed the SD 2 bomb. The wings and arming spindle remained attached to the bomb after the fuze had armed itself, as the bomb descended towards the ground. Butterfly bombs contained the kleine Zündladung 34 (kl. Zdlg. 34/Np with a blasting cap and 7 grams of Nitropenta) booster and the main explosive filling consisting of 225 grams of cast Füllpulver 60/40 (Amatol) explosive. The fragmentation density produced by an SD 2 was 1 fragment per m2 in 8 meters radius from a ground burst SD 2 bomb; overall, the body of an SD 2 produced about 250 fragments with a mass of over 1 gram and a still greater number of lighter fragments. The fragments were generally lethal to anyone within a radius of 10 metres (33 ft) and could inflict serious fragmentation injuries (e.g. deep penetrating eye wounds) as far away as 100 metres (330 ft). Butterfly bombs were usually painted either straw yellow (desert camouflage), or, if fitted with the DoppZ (41) or (41) A fuze, dark green or grey.

Butterfly bombs could be fitted with any one of three fuzes, which were made of aluminium and stamped with the model type surrounded by a circle:

  • 41 fuze – has an external selector switch with two settings. The Zeit (time) setting will detonate the bomb in the air, approximately five seconds after being armed. The "AZ" (Aufschlagzünder - impact) setting triggers detonation when the bomb hits the ground. The fuze is armed if 4 screw threads at the base of the arming spindle are visible. This fuze is highly sensitive to disturbance if the selector switch is set to Zeit and the bomb is unexploded. The particular switch setting of any type 41 fuze is clearly visible on its exterior.
  • 67 fuze – clockwork time delay. Time of detonation can be set between 5 and 30 minutes after arming itself in the air. This fuze also has an external selector switch for impact detonation. The particular switch setting of any type 67 fuze is clearly visible on its exterior.
  • 70 fuze – anti-handling device (i.e. booby trap) will trigger detonation if the bomb is moved after impact with the ground. The fuze is armed if three screw threads at the base of the arming spindle are visible.

Butterfly bombs in a submunitions container could have a mixture of different fuzes fitted to increase disruption to the target. Additionally, when a single fuze type with two operating functions was fitted (e.g. type 41), bombs in a submunitions container could have either or both possible fuze settings selected by the Luftwaffe ground crew. Fuze variants such as the 41A, 41B, 70B1, 70B2, etc., also existed. These variants were inserted into the fuze pocket via a bayonet fitting (the fuze was held in place via two steel clips) but otherwise functioned identically.

As with more modern cluster bombs, it was not considered practical to disarm butterfly bombs which had fully armed themselves but failed to detonate. This was because SD 2 fuzes were deliberately designed to be extremely difficult and dangerous to render safe once they had armed themselves. Instead, the standard render safe procedure for any unexploded SD 2 butterfly bomb was to evacuate the area for at least 30 minutes (in case the bomblet was fitted with a type 67 time delay fuze), then surround it with a ring of sandbags (to contain the explosion) and destroy it in situ by detonating a small explosive charge beside it. Other solutions were to attach a long string to the bomb and tug on it after taking cover, or for bombs in open countryside, shooting at them with a rifle from a safe distance.

Not all unexploded SD 2 butterfly bombs still have their wings attached. In some cases the wings have rusted away and fallen off. The SD 2 then resembles a rusty tin can with an aluminium disc (the fuze) in its side, sometimes with a short stub projecting from it. Regardless of age and condition, all unexploded SD 2s remain highly sensitive to disturbance and can easily detonate.

Use

[edit]

Butterfly bombs were first used against Ipswich in 1940, but were also dropped on Kingston upon Hull, Grimsby[3] and Cleethorpes in June 1943, amongst various other targets in the United Kingdom.[4] Lieutenant Colonel Eric Wakeling led the clearance of the unexploded ordnance in Grimsby within the Royal Engineers.[5] They were subsequently used against Allied forces in the Middle East.[6] The British Government deliberately suppressed news of the damage and disruption caused by butterfly bombs in order to avoid encouraging continued use by the Germans. On October 28, 1940, some butterfly bombs that had failed to arm themselves properly were discovered in Ipswich by British Army ordnance technicians Sergeant Cann and 2nd Lieutenant Taylor. By screwing the arming rods back into the fuzes (i.e. the unarmed position) they were able to recover safe examples of the new weapon system to allow the British to reverse-engineer and understand the mechanism.[7]

The SD 2 saw use in the opening stages of Operation Barbarossa, the German invasion of the Soviet Union which began on 22 June 1941. Twenty to thirty aircrews had been picked to drop SD 2s and SD10s (10 kg submunitions) on key Soviet airfields, a flight of three aircraft being assigned to each field. The purpose of these early attacks was to cause disruption and confusion as well as to preclude dispersion of Soviet planes until the main attack was launched.[8] It was reported that Kampfgeschwader 51 lost 15 aircraft due to accidents with the SD 2s – nearly half of the total Luftwaffe losses that day.[9]

Luftwaffe monthly consumption of the SD 2 increased from 289,000 examples in the summer of 1941 to 436,000 in July 1943 and 520,000 in August 1943. This increase was nowhere near high enough to match the Luftwaffe senior leadership's demands.[10]

The AB 250-2 cluster bomb could carry 144 SD 2 anti-personnel submunitions, or 40 of the anti-armor SD-4 submunitions. While the AB 250-3 could carry 108 SD 2s. AB 250s were most frequently carried by the Focke-Wulf Fw 190 F/G series, but in practice, they could be lifted by a wide variety of aircraft, including the Me 262. Because of Hitler's interference, these jet-powered fighters were pressed into service as a Jabo (Jagdbomber, fighter-bomber), a role for which they were poorly suited. Notably, Me 262s were sent on nuisance raids against Eindhoven in early October, loaded with AB 250 bomblet dispensers.[11]

The last recorded UK death from a German butterfly bomb in England occurred on November 27, 1956, over 11 years after the end of the war: Flight Lieutenant Herbert Derrington[12][13] of the RAF was examining an SD 2 at the "Upminster bomb cemetery" (some remote sandpits situated East of RAF Hornchurch, where explosive ordnance disposal experimental and research work took place) when it detonated. He died of shrapnel and blast injuries at Oldchurch Hospital the same day.[14]

On the island of Malta in 1981 Paul Gauci, a 41-year-old Maltese man, died after welding a butterfly bomb to a metal pipe and using it as a mallet, thinking it was a harmless can.[15] The latest find of such a bomb was on 28 October 2009, by an 11-year-old boy in a secluded valley close to a heavily bombarded airfield. This bomb was safely detonated on-site by the Armed Forces of Malta.[15]

[edit]
  • Photo of an SD 2 from Civil Defence Training Pamphlet No 2: Objects Dropped From The Air (3rd Edition).
    Photo of an SD 2 from Civil Defence Training Pamphlet No 2: Objects Dropped From The Air (3rd Edition).
  • AB 23 submunition dispenser.
    AB 23 submunition dispenser.
  • AB 24T submunition dispenser.
    AB 24T submunition dispenser.
  • AB 70-3 submunition dispenser.
    AB 70-3 submunition dispenser.
  • AB 250-1 submunition dispenser.
    AB 250-1 submunition dispenser.
  • AB 250-3 submunition dispenser.
    AB 250-3 submunition dispenser.

US copy

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The United States manufactured a copy of the SD 2 for use during World War II, the Korean War and Vietnam War, designating it the M83 submunition.[16] The 3 fuze types used on the M83 submunition were slightly modified versions of the original German designs:

  • M128A1 - airburst or impact fuze. Airburst detonation occurred 2.5 seconds after arming. Detonation on impact was instantaneous. The fuze setting is clearly marked on the exterior and was selectable by ground crew
  • M130A1 - clockwork time fuze with time delays ranging from 10, 20, 30, 40, 50 or 60 minutes. Has no markings, but is recognisable by the square-shaped fitting for the arming spindle
  • M131A1 - anti-disturbance fuze. Detonation triggered when the device was disturbed. Has no markings, but is recognisable by the pentagonal-shaped fitting for the arming spindle

The 4-pound (1.8 kg) M83 fragmentation bomblet was used in the US M28 and M29 cluster bombs.

  • US M83 cluster bomb with wings closed. The fuze has not yet armed itself
    US M83 cluster bomb with wings closed. The fuze has not yet armed itself
  • US M83 cluster bomb with wings deployed.
    US M83 cluster bomb with wings deployed.
  • 500 lb M29 cluster bomb with ninety M83 submunitions inside it
    500 lb M29 cluster bomb with ninety M83 submunitions inside it

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Butterfly Bomb

View on Grokipedia
from Grokipedia
The Butterfly Bomb, officially designated the SD 2 (Sprengbombe Dickwandig 2 kg), was a 2-kilogram anti-personnel submunition developed and deployed by the German during the Second as part of early cluster bomb systems. Consisting of a thin sheet-steel cylindrical body approximately 8 cm long, it featured hinged halves that split open in flight under spring tension, with attached vanes that stabilized descent, imparted spin to arm the , and gave the device its distinctive butterfly-like appearance. Filled with 225 grams of TNT explosive, the bomblet was fitted with sensitive fuzes such as the impact/time-delay Type 41 or the anti-handling Type 70, making it highly dangerous to touch or disturb, with a lethal fragmentation radius of up to 25 meters and potential for injuries extending to 150 meters. Introduced as the world's first operational , the Butterfly Bomb saw its initial combat use on 29 October 1940, when German aircraft dropped clusters over in , . It was subsequently employed in numerous raids on British targets, including in 1940 and more devastating attacks on , , and in June 1943, where over 1,000 SD-2 bomblets were scattered in a single assault on , causing widespread terror, civilian deaths, and injuries due to the bomblets' tendency to lodge in grass, roofs, or soil without immediate detonation. The bombs were typically dispensed from larger aerial containers like the AB 23 (holding 6 bomblets) or AB 250-3 (up to 108), which burst at altitude to disperse the submunitions over areas up to 200 meters wide, targeting personnel and disrupting ground operations. Often painted field grey with yellow bands or red stripes for identification, these devices were also used in , such as at , where Allied forces recovered examples amid the 1942 battles. The Butterfly Bomb's design proved influential, inspiring similar submunitions like the American M83 used in the Korean and Wars, and it highlighted the psychological and persistent hazards of cluster weapons. British authorities issued public warnings through posters and broadcasts from to , urging civilians not to handle suspected devices and to report them to air raid wardens or police, as the bomblets' vibration-sensitive fuzes could trigger delayed explosions. Postwar, remained a threat; the last recorded death in the from a Butterfly Bomb occurred in 1956, underscoring the long-term dangers of such scatterable munitions.

History and Development

Origins and Design Intent

The Butterfly Bomb, designated SD 2 (Sprengbombe Dickwandig 2 kg), emerged from German engineering efforts in the late 1930s to fulfill requirements for a compact, scatterable anti-personnel submunition capable of targeting formations and areas with minimal to buildings or . This design prioritized fragmentation effects over high-explosive power, allowing deployment in large numbers to cover extensive ground without the structural devastation associated with heavier bombs. As a core component of early cluster munitions, the SD 2 was engineered to enhance area denial through its dispersal mechanism, releasing dozens of bomblets from containers to saturate targets and impede enemy movement. The intent extended to psychological disruption, achieved via specialized fuzes enabling delayed detonation or anti-handling sensitivity, which deterred recovery operations and sustained fear among affected populations long after initial attacks. These features made it a harassing suited to the Luftwaffe's tactical doctrine of disrupting rear areas and morale without committing resources to prolonged engagements. Development progressed rapidly in the late , with the SD 2 first used operationally on 28 October 1940 over , , marking its debut as the first purpose-built scatterable anti-personnel system in combat history. Prototypes and initial variants were refined for compatibility with containers like the AB 23, which carried 23 bomblets and ensured even distribution upon release from such as Ju 88s and Do 17s. This innovation reflected the Luftwaffe's pre-war emphasis on versatile aerial ordnance for rapid territorial gains in a mechanized conflict.

Initial Production and Deployment

Mass production of the SD 2 Butterfly Bomb commenced in 1940, as part of the Luftwaffe's efforts to develop effective anti-personnel munitions. The bomb's design featured a body filled with approximately 225 grams of TNT, enabling fragmentation upon detonation, and was produced in significant quantities for widespread deployment throughout the war. To facilitate aerial dispersal, the SD 2 was packed into cluster bomb containers such as the AB 250-3, which accommodated 108 bomblets within a thin sheet housing that split open in flight via torsion springs, scattering the submunitions over targeted areas. This integration allowed for efficient coverage of personnel concentrations from , marking an early innovation in cluster weaponry. Other containers, like the AB 23 holding 23 bomblets, were also employed depending on mission requirements. The first operational deployment occurred in 1940, with Butterfly Bombs dropped over , , on , where British ordnance teams recovered incompletely armed examples, indicating initial challenges in fuze activation reliability. These early uses served to test and refine the bomb's performance in real conditions, leading to adjustments in the arming process. Logistical aspects of production included variations in external coloring to enhance and adapt to different theaters, with bodies painted black, lead-grey, red, yellow, or field grey, often accented by yellow or red bands on the wings. Yellow schemes supported operations, while green-grey finishes were prioritized for European environments; these adaptations balanced operational concealment with manufacturing efficiency amid wartime resource constraints.

Design and Components

Physical Structure

The Butterfly Bomb, designated as the SD-2 (Sprengbombe Dickwandig 2 kg), features a compact cylindrical body measuring approximately 79 mm in length and 76 mm in diameter, with a wall thickness of about 10 mm, designed to house the explosive payload while ensuring effective fragmentation upon . This body includes a transverse pocket on its side for inserting the arming mechanism, and its interior is coated with a composition to protect the filling and facilitate the exploder cavity. The total weight of the assembled bomblet is 2 kg, making it lightweight for aerial dispersal in large clusters. Encasing the cast iron body is a thin sheet steel outer container composed of four hinged sections—two curved side pieces and two end flaps—that form the distinctive "wings" responsible for the bomb's name and function. These wings are connected by a hinge bar and secured by a safety pin during storage and carriage; upon release from the parent container, torsion springs cause them to deploy outward, creating a butterfly-like profile that stabilizes the descent, induces spin for arming, and aids in scattering over a wide area. The deployed configuration spans roughly 310 mm in height, 240 mm in length, and 140 mm in width, enhancing aerodynamic performance while mimicking innocuous debris to evade detection. At the core of the design is a central burster well containing approximately 212 g of cast TNT explosive charge, surrounded by a layer of bitumen for added stability and to prevent premature detonation. This filling is optimized for high-explosive fragmentation, where the detonation shatters the thick cast iron casing into numerous lethal shards, maximizing anti-personnel effects through the bomb's simple yet robust construction. Externally, the bomblet often bears painted markings for identification, including a red stripe on the end plates against a yellow or field grey background, with variations in color such as black or lead-grey reported across production batches.

Fuze Systems and Arming

The fuze systems of the Butterfly Bomb (SD-2) were designed to arm reliably during descent while incorporating multiple detonation modes to enhance its anti-personnel effectiveness. The primary fuze, designated as the (41) or Type 41 mechanical clockwork , was a zinc-alloy cased device that could be selectively set via a screw for either "Zeit" (time delay for airburst) or "AZ" (impact) . In the Zeit setting, it provided a short delay of approximately 2 to 5 seconds after arming, resulting in airburst at low altitudes typically between 1 and 10 meters depending on descent speed, which scattered fragments over a wider area. The AZ setting ensured immediate upon ground impact. This was screwed directly into the bomb body for secure installation. The arming sequence commenced upon release from the cluster container, when torsion springs caused the bomb's sheet-metal wings to deploy and form a stabilizing parachute-like . These wings, functioning as vane-driven windmills, induced of the during fall, which in turn unscrewed the arming spindle connected to the after three to six revolutions, fully withdrawing the safety bolt and unmasking the striker channel after about 3 seconds. A bore-riding safety within the mechanism further prevented premature initiation by blocking the striker until sufficient occurred, ensuring the device remained safe during handling and initial dispersal. For delayed and anti-handling capabilities, the Type 67 was employed, featuring an adjustable for delays ranging from 5 to 30 minutes to facilitate post-drop explosions that could catch responders off guard. This was pushed into the and secured by projections fitting into casing slots, with arming achieved by vane rotation withdrawing an arming rod about 1/4 inch to start the . Complementing this, the Type 70 (variants A and B) provided anti-disturbance functionality, triggering upon tilt, , or handling after a brief post-impact delay of around 5 seconds in the B variant; the A variant incorporated longer chemical delays up to 30 hours. Like the Type 67, it was installed via slot projections and armed through spindle withdrawal, enhancing the 's hazard persistence on the ground.

Operational Employment

Use in European Theater

The Butterfly Bomb, known technically as the SD 2, saw its first combat deployment by the in October 1940 over , , as part of the early Blitz bombing campaign targeting British cities. These initial attacks involved cluster containers dispersing the bomblets over urban areas to maximize anti-personnel effects, marking one of the earliest uses of cluster munitions in . British ordnance teams recovered several unexploded units shortly after the raid, allowing analysis of their design and mechanisms. In 1943, the weapon featured prominently in raids on northeastern English port towns, including , , and , during a renewed effort to disrupt Allied shipping and morale. On June 14, 1943, a major attack on and released thousands of the bomblets alongside conventional explosives, scattering them across residential areas, docks, and streets; this assault alone caused over 60 civilian deaths and hundreds of injuries, with many fatalities occurring post-raid as residents disturbed the delayed-action devices. Similar deployments over Hull in the same month targeted industrial sites, exacerbating disruption in these key fishing and trade hubs vital to the . The bomblets' tendency to lodge in trees, roofs, and gardens prolonged the danger, hindering recovery efforts and cleanup. On the Eastern Front, the Butterfly Bomb was employed starting with in June 1941, where bombers, including Ju 88s, dispersed SD 2 clusters over Soviet airfields, troop concentrations, and urban centers to deny area access and fragment formations. During the advance toward Leningrad, these munitions were used in support of ground operations, with aircraft carrying up to 360 bomblets per to saturate targets and impede Soviet ; their lightweight design allowed wide dispersal, contributing to the psychological and tactical strain on defenders amid the siege. Production limitations eventually curtailed their scale, but they remained a staple in anti-personnel roles throughout the campaign. British authorities responded to the bombs' unpredictable nature by issuing targeted warnings through posters and , advising civilians to report sightings to wardens without handling them, while restricting detailed media coverage to prevent widespread panic and further exploitation of fear. By the war's end, the had documented thousands of such incidents, underscoring the weapon's role in sustained aerial harassment.

Tactical Applications and Effects

The Butterfly Bomb, or SD-2 submunition, was tactically deployed by the in cluster containers such as the AB 23 or AB 250, which held up to 23 bomblets each and were released from medium bombers including the and to achieve broad dispersal patterns over targeted zones. These containers burst open mid-air via time or impact fuzes, scattering the bomblets to cover areas up to several hundred meters wide, primarily against troop concentrations, soft targets like vehicles, and urban districts to maximize anti-personnel disruption and deny terrain to the enemy. The design emphasized area denial, with the bomblets' stabilizing vanes and parachutes ensuring even distribution during descent. The weapon's effectiveness stemmed from its fragmentation capabilities and psychological terror, as the thick cast-iron casing produced over 200 high-velocity shards upon detonation, lethal within a 25-meter radius and capable of inflicting penetrating injuries up to 150 meters away. Delayed-action fuzes (up to 30 minutes or more) and anti-handling variants, such as the 70-series, detonated upon disturbance, simulating minefields and forcing troops and civilians to avoid affected areas, thereby amplifying operational delays and morale impact during raids. This combination of immediate blast effects and prolonged threat made the SD-2 particularly suited for harassing unarmored forces and sowing confusion in contested environments. Civilian impacts were severe due to the bomblet's design for "soft" targets, with its compact size (about 8 cm long) and wing-like vanes often leading children to mistake unexploded units for toys, resulting in accidental handling and detonation. In the UK, such deployments caused widespread casualties among non-combatants; for instance, during June-July 1943 raids on and , around 3,000 SD-2s were scattered, killing 114 people—over half the total deaths from 37 raids on the region across the war—and injuring many more while instilling paralyzing fear that disrupted daily life and . The psychological strain was acute, as the unpredictable anti-disturbance fuzes turned ordinary landscapes into hidden dangers, exacerbating trauma in bombed communities. British countermeasures focused on specialized bomb disposal units within the Royal Engineers, trained to identify SD-2 variants and mitigate risks through methods like erecting barriers around clusters, waiting at least 30 minutes for time fuzes to expire, and remotely detonating devices with small charges or pull-ropes from covered positions. Despite these protocols, the fuzes' sensitivity to movement led to high failure rates in handling, with several disposal personnel killed by premature explosions during WWII operations, underscoring the bomblet's role in endangering even trained experts.

Variants and International Copies

German Fuze Variants

The German developed several specialized variants for the SD-2 Butterfly Bomb to improve its operational flexibility, including adaptations for delayed action and anti-disturbance capabilities, beyond the standard impact or time fuzes. These modifications addressed limitations in early designs, such as the need for tactical versatility in cluster deployments. The standard fuze was the Type 41, a mechanical device with a case and / mechanism, arming in 2.3-3.5 seconds for aerial burst or impact . The Type 41A variant, used in the SD 2B, featured similar but with a joint and V-shaped vanes, arming in 2.9-3.5 seconds. The Type 79 (A/B) was an aerial burst with settings for at altitudes of 1000-1900 meters or 1900-2500 meters, used in containers like AB 23 and AB 24T. Other variants included the Z 69D, an electrical impact fuze with a 1-second delay, used in AB 70-3 and AB 250-1 containers, and the (89)B electrical fuze for AB 250-3. The (69) series electrical fuzes were employed in AB 250-2. The Type 67 provided a delay of 5-30 minutes. Anti-tamper enhancements were integrated into the Type 70 fuze series. The Type 70A was a chemical-mechanical fuze with approximately 5 minutes arming time and a 4-30 hour delay, including self-destructive features. The Type 70B (and 70B/1) employed a clockwork anti-disturbance system that armed 5 seconds post-impact and triggered on any subsequent tilt or vibration, with delays of about 0.5 seconds on descent, 5 seconds on impact, and 1 second on disturbance; these built on the core arming process of wind-driven rotation to ensure reliability in contested environments. Markings such as "8/42" indicate production in 1942 for the Type 70A. Variants were fitted via threaded (SD 2A) or bayonet (SD 2B) attachments to the bomb's side pocket.

United States M83 Adaptation

The developed the M83 submunition as a reverse-engineered adaptation of captured German SD-2 Butterfly Bombs during , with initial documentation appearing in late 1943. This design drew inspiration from the original German bomblet's aerodynamic dispersal mechanism but incorporated modifications for mass production and compatibility with American delivery systems. The M83 retained the core concept of a lightweight, winged anti-personnel fragmentation device intended for aerial cluster deployment against troop concentrations and soft targets. Key differences from the German original included a fully construction for the cylindrical body, cast in two halves and welded together, which reduced costs compared to earlier prototypes while maintaining durability. The M83 weighed approximately 1.8 kg (4 lb) overall, with 0.45 kg (1 lb) of high explosive filler, typically Composition A or TNT, to produce lethal fragmentation upon detonation. Its "butterfly" wings and stabilizing vanes, made of sheet , folded around the body for clustering and deployed via an arming cable during release, ensuring wide-area scatter similar to the SD-2. The M83 was primarily integrated into the M29 500 lb cluster adapter, which held 90 such bomblets in nine "wafer" assemblies of ten each, allowing for efficient aerial delivery from bombers and fighters. The M83 employed several fuze variants to enhance versatility in operational scenarios. The M129 series provided impact or airburst functionality, with settings for ground detonation on contact or delayed aerial explosion. The M130 series offered time-delay options for delayed surface bursts for area denial. For anti-handling protection, the M131 series incorporated a mechanism armed by the deploying wings, functioning as an anti-disturbance that detonated if the bomblet was moved after landing. These fuzes were internally installed in a 1.75-inch threaded cavity, with clusters typically mixing types for varied effects. Deployment of the M83 began in the Pacific Theater during the latter stages of , primarily against Japanese positions, though production scaled up significantly postwar. It saw extensive use in the (1950–1953) for and , followed by widespread application in the from 1965 to 1973, where millions of units were produced and dispersed via cluster bombs to target enemy supply lines and fortifications. The M83's effectiveness in scattering over large areas made it a staple of U.S. anti-personnel ordnance through these conflicts.

Legacy and Post-War Impact

Unexploded Ordnance Hazards

The Butterfly Bomb, or SD 2 submunition, exhibited a failure rate of approximately 10% during World War II, consistent with broader estimates for German aerial ordnance dropped on the United Kingdom. This malfunction rate, attributed to manufacturing defects, improper arming by aircrews, or environmental factors upon impact, resulted in thousands of unexploded devices remaining embedded in soil, structures, and urban landscapes across Britain. Post-war clearance efforts by Royal Engineers and civilian teams recovered many, but an estimated significant number—potentially tens of thousands when accounting for cluster dispersals—persisted as hazards, particularly in heavily bombed areas like London, Grimsby, and Ipswich. The lingering threat manifested in fatal incidents well into the post-war era, underscoring the bomblets' delayed-action fuzes and anti-handling mechanisms. The last recorded death in the UK from an unexploded Butterfly Bomb occurred on November 27, 1956, when Royal Air Force Flight Lieutenant Herbert Denning was killed while attempting to defuse what he believed to be a training device at the Upminster bomb cemetery near RAF Hornchurch, England; the incident highlighted the risks to even trained personnel handling aged ordnance. Discoveries continued sporadically, with unexploded SD 2s surfacing during construction and excavation works; for instance, a Butterfly Bomb was recovered in Nottingham in 2014 from a private collection, prompting EOD intervention. In other European theaters, similar hazards persisted: in Malta, heavily targeted by Luftwaffe raids, unexploded WWII ordnance including cluster submunitions has been uncovered in rural areas, such as a German bomb found by a child in Wied Qirda in 2009, requiring Armed Forces of Malta disposal. In former Soviet territories, where dispersed vast quantities of SD 2s across and , unexploded remnants of WWII ordnance contribute to ongoing operations. Corrosion over decades exacerbates instability, as the thin sheet-steel casing and chemical fuzes degrade, potentially leading to spontaneous or heightened sensitivity to disturbance; studies on WWII UXO indicate that environmental exposure increases volatility, with rusted components failing unpredictably during handling. Disposal of discovered Butterfly Bombs relies on explosive ordnance disposal (EOD) protocols emphasizing minimal manipulation due to the devices' compact size and sensitive fuzes (such as the 41 or 17 types), which incorporate anti-disturbance features. Standard procedures involve evacuating a 30-meter radius for at least 30 minutes to allow any time-delay mechanism to expire, followed by in-situ controlled detonation using donor charges; X-ray imaging may assess fuze condition in accessible cases, but direct intervention is avoided to prevent triggering. In the UK, EOD teams from the British Army's 29 Explosive Ordnance Disposal and Search Regiment handle such operations, prioritizing remote assessment via robotics where feasible. Modern risks from unexploded Butterfly Bombs center on development in former drop zones, where construction sites and agricultural activities unearth buried submunitions; plowing or groundwork can dislodge them, leading to injury or explosion. In the UK, WWII UXO incidents prompt hundreds of annual EOD callouts, with tri-service teams responding to about eight incidents daily across all ordnance types, though cluster remnants like the SD 2 pose unique challenges due to their scatter pattern and small footprint. These hazards necessitate pre-construction UXO risk assessments, particularly in eastern England where 1943 raids were concentrated.

Influence on Modern Cluster Munitions

The SD-2 Butterfly Bomb pioneered the technological concept of cluster munitions through its use of lightweight, aerodynamic submunitions designed to scatter over a wide area upon release from a carrier bomb, a principle that became foundational to post-World War II designs emphasizing area-denial and anti-personnel effects. This scatter pattern allowed for coverage of larger targets with multiple small explosives, influencing the development of modern systems that prioritize similar dispersion for tactical versatility, as seen in the enduring design echoes in contemporary cluster weapons. The ' M83 submunition, a direct wartime adaptation of the SD-2, further propagated this approach into later U.S. munitions like the CBU-87. The Butterfly Bomb's demonstrated indiscriminate nature and high failure rates contributed to international recognition of cluster munitions as a humanitarian concern, culminating in the 2008 , which prohibits their use, production, stockpiling, and transfer. Ratified by 112 states parties as of September 2025, the treaty excludes major producers such as the and , yet mandates stockpile destruction and clearance of contaminated areas to mitigate long-term risks. In compliance, destroyed over 50,000 tonnes of its cluster munitions stockpiles, including more than 60 million submunitions, by 2015—three years ahead of the convention's deadline. Ethical debates surrounding cluster munitions often cite the SD-2 as an early exemplar of weapons causing disproportionate civilian harm, with its unexploded remnants posing persistent threats akin to de facto landmines, fueling advocacy by groups like Handicap International for global bans based on documented victim impacts. These campaigns emphasize the moral imperative to address submunition duds, which historically and currently endanger non-combatants long after conflicts end. In modern conflicts, such as the during the , cluster munitions have proliferated despite the convention, with Syrian and forces deploying them extensively, resulting in widespread that mirrors the Butterfly Bomb's failure rates and creates enduring hazards for civilians. This continued use underscores the treaty's challenges in enforcement, as submunitions contaminate agricultural and populated areas, exacerbating humanitarian crises.

References

  1. https://www.awm.gov.au/collection/C148379
  2. https://www.b17museum.ch/news_e.php?id=91
  3. https://www.nationalarchives.gov.uk/education/resources/home-front-1939-1945-part-one/butterfly-bomb/
  4. https://commons.lib.jmu.edu/cgi/viewcontent.cgi?filename=0&article=2401&context=cisr-globalcwd&type=additional
  5. https://man.fas.org/dod-101/sys/land/docs/981100-schneck.htm
  6. https://stephentaylorhistorian.com/wp-content/uploads/2020/09/op-1666-german-explosive-ordnance-volume-1.pdf
  7. http://michaelhiske.de/Allierte/USA/TManual/9_1985_2/Chap01/FIG_039.HTM
  8. https://www.iwm.org.uk/collections/item/object/30020459
  9. http://michaelhiske.de/Allierte/UK/Handbook/Pamphlet03/03_001.HTM
  10. https://www.iwm.org.uk/collections/item/object/30023426
  11. http://www.lonesentry.com/articles/ttt34/german-ww2-butterfly-bomb.html
  12. https://bombfuze.net/history_of_bomb-disposal.html
  13. https://www.theguardian.com/uk/the-northerner/2013/jun/21/butterfly-bombs-luftwaffe-cleethorpes-grimsby
  14. https://www.grimsbytelegraph.co.uk/news/nostalgia/butterfly-bombs-bring-terror-morning-1683109
  15. https://www.youtube.com/watch?v=kj8mT6Z_LEY
  16. https://www.dangeruxb.co.uk/sd2-butterfly-bomb.html
  17. https://warhistory.org/%40msw/article/sd-2-schmetterling
  18. https://www.dangeruxb.co.uk/royal-engineers-bomb-disposal.html
  19. https://www.bocn.co.uk/threads/butterfly-bomb-sd2-and-m83-collection.81823/
  20. https://cat-uxo.com/uxo-types/submunitions/m83-submunition
  21. https://bulletpicker.com/cluster_-500-lb-frag_-m29.html
  22. https://bulletpicker.com/pdf/OP-1664-V2.pdf#page=65
  23. https://bulletpicker.com/bomb_-4-lb-frag_-m83.html
  24. https://bulletpicker.com/antidisturbance_-m131_-m131a1.html
  25. https://bulletpicker.com/pdf/OP-2216-1960.pdf#page=282
  26. https://www.inert-ord.net/usa03a/usa6/bfly/index.html
  27. https://bulletpicker.com/pdf/OP-1280-1955.pdf#page=150
  28. https://www.london.gov.uk/media/110496/download?attachment
  29. https://cemex.hambleparishcouncil.gov.uk/wp-content/uploads/sites/5/2022/01/Vol-2-Appendix-8.4-UXO-Risk-Assessment.pdf
  30. https://www.bbc.co.uk/news/uk-england-nottinghamshire-27679935
  31. https://www.independent.com.mt/articles/2009-10-30/news/wartime-german-bomb-found-by-boy-265489/
  32. https://commons.lib.jmu.edu/context/cisr-globalcwd/article/2613/viewcontent/Full_Aging_Study_all_FINAL.pdf
  33. https://www.forcesnews.com/services/army/inside-rigorous-training-and-testing-army-bomb-squads
  34. https://www.bbc.com/news/uk-43061244
  35. https://www.gichd.org/fileadmin/uploads/gichd/Publications/Guide-to-Cluster-Munitions-June2009.pdf
  36. https://www.wired.com/story/russia-ukraine-cluster-bombs/
  37. https://www.hrw.org/sites/default/files/related_material/munitionChart061507.pdf
  38. https://www.clusterconvention.org/
  39. https://www.auswaertiges-amt.de/en/newsroom/news/218510-218510
  40. https://www.clusterconvention.org/files/external_publications/Cluster_Munitions_Circle_of_Impact.pdf
  41. https://www.hrw.org/report/2010/11/22/meeting-challenge/protecting-civilians-through-convention-cluster-munitions
  42. https://www.hrw.org/news/2016/07/28/russia/syria-widespread-new-cluster-munition-use
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