Imitation is the Sincerest Form of Flattery: How the U.S. Took a German Ordnance Item for its Own, by Thomas A. Crawford

Imitation is the Sincerest Form of Flattery: How the U.S. Took a German Ordnance Item for its Own

Thomas A. Crawford

Introduction

While history is resplendent with examples of one belligerent using the tactics and weapons of another, it is less known the United States has done this as well; especially in the twentieth century. Yes, most know of the importation of former German scientists for our fledging rocket program that ended with the Apollo Moon landings; however simpler, more lethal examples are lesser known.

By being able to learn about and following the development of German ordnance supplied to the United States by Great Britain prior to our entry into World War II, the United States had a better start on countering the current threat. These threats were not insignificant, learning to counter some of the first submunitions developed and deployed for the sole purpose of denying areas to troops and causing civilian displacement. Utilizing inerted specimens of the German SD–2“Schmetterling” (butterfly), U.S. Army Picatinny Arsenal conducted tests and produced a copy of this munition for our own use. These were initially classified as 4 pound fragmentation bomb T10, with fuzes T47, 48, and 49; later given the proper type approved nomenclature, M83 with fuzes M129, M130, and M131. The fuzes as produced for use in the American copied bomb, performed in the same manner as the German original, just with slightly simplified construction. These small changes were employed solely to increase and simplify production and their leading to increased quantities of bombs in less time.1

In addition, the design of the bomb was simplified in order to facilitate yet another increase in its rate of manufacture. The U.S. design yielded a weapon produced in two equal halves, welded together around its circumference; whereas the German design produced a bomb made as a single piece. This unique difference is a feature used today as a positive means of identification feature in the field by Explosive Ordnance Disposal personnel. The M83 4-pound Fragmentation Bomb, was finally classified as obsolete in 1975, but not before it was supplied to other countries as a result of the participation by the United States Mutual Defense Aid Programs. Deplopyment of these “Butterfly Bombs” can still be encountered in the fields of foreign nations today. This is a lasting legacy indeed for German ordnance technicians.2

A Detailed Description of the German Bomb

The “Butterfly Bomb” (or Sprengbombe Dickwandig 2kg or SD–2) was a 2-kilogram anti-personnel submunition used by the Luftwaffe during World War II. It was so named because its thin cylindrical metal outer shell when hinged open when during deployment gave it the

FIG 1. Field warning sign used in European Theater. Courtesy of U.K. MoD/ U.S. Army Historical Archives.

superficial appearance of a large butterfly. The distinctive design of this antipersonnel weapon made it easy to recognize. SD–2bomblets were not dropped individually, but were packed into containers holding between 6 to 108 submunitions e.g., the AB 23 SD–2and AB 250–3 submunition dispensers, or carried on under wing racks that dropped the submunitions in series or salvos. The SD–2 submunitions were individually released after the container was dropped by the aircraft and respectively burst open. Owing to the fact SD2s were always dropped in groups (never in singlet) the discovery of one unexploded SD–2 was a reliable indication any number of bombs had been dropped nearby.3 This bomb device 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 and released the SD–2 bomblets and scattering them into the air were alternatively referred to as the “Devil’s Eggs” by Luftwaffe air and ground crew.4 The SD–2 were targeted against British cities, often being dropped in combination with other high explosive and incendiary ordnance. A relatively small weapon, its primary purpose was as an area denial, anti-personnel

FIG 2. Current use bombing range / impact sign. Courtesy of the author. bomblet, and booby-trap device. The primary intention of its use was to slow the progress of troops, create much needed repair of bomb damage, and terror inducement following a bombing raid.5

A common configuration for the SD–2 was to load them into a container with a capacity for twenty-three bomblets whose appearance resembled that of a standard 50kg-HE bomb.

The AB–250 bomblet dispenser would hold 144 of the anti-personnel SD–2 submunitions, or 30 of the anti-armor SD–4 submunitions.6 AB–250s were most frequently carried by the Focke-Wulf–190F/G series aircraft. However, AB–250s could be carried by a wide variety of aircraft, up to and including the infamous Me–262 jet fighter-bombers. Me–262s were sent on nuisance raids against Eindhoven in early 1945 loaded with AB–250 bomblet dispensers.7

FIG 3. Luftwaffe ground crew loading SD–2s on JU–87. Courtesy of LuftAchive.de. FIG 4. Modern model of the under wing bomb rack system used on various Luftwaffe aircraft to carry single SD–2s, also the open shipping crate showing the shipping configuration. Courtesy of Eduard Bassin, Master Modeler.

Functional Description of the Individual Bomblets (Submunition)

Following the bomblet’s release, torsion springs pop the wings open. Air drag pulls the spring-loaded assembly to the end of the connecting cable piece where it sets and, in turn, locks it into the wing’s body. This assembly proceeds to rotate, unscrewing the threaded arming spindle from the fuze body itself. This thread has a stop that keeps it from completely becoming detached from the body of the bomb assembly. Once the spindle completes about ten turns, the released parts of the fuze, rotate into an armed position. Once armed, insitu disarmament was not possible. The bomblet had to be destroyed in place, thereby making damage to property and the risk of injury or death unavoidable.8

These diminutive but lethal devices were found on roofs, on beds, hanging by one wing through ceilings, and the only way for the bomb disposal squads to deal with them was to blow them up with a charge wherever they happened to be.

Com. Sir Aylmer Firebrace, C.B.E., R.N., Chief of Fire Staff, British National Fire Service, wrote:

A Grimsby, UK, fireman told me “they tied the whole town up for three days—everything came to a standstill.” A German prisoner of war told our bomb disposal people the Luftwaffe dropped some containers of butterfly bombs onto a race course near Paris in order to give their bomb disposal squads the experience of coping with them. The result was a number of German casualties. Very thorough.

Historical Notes

The German Schmetterling (Butterfly) bombs were first used against Britain at Ipswich, in 1940, but were also dropped on Kingston, Hull, and Grimsby and upon Cleethorpes in June 1943. Additional attacks were carried out elsewhere in the United Kingdom. These bomblets were subsequently used against Allied forces starting in the Middle East. The British government deliberately suppressed news of the damage and disruption caused by butterfly bombs in order not to encourage the

Germans to keep using them. On 28 October 1940, some butterfly bombs that had incompletely armed themselves were discovered in Ipswich by British bomb disposal technicians Sergeant Cann and 2d Lieutenant Taylor. By screwing the arming rods back into the fuzes (i.e. the unarmed position) the two men were able to recover safe examples of how to reverse engineer.9

The SD–2 saw use in the opening stages of Operation Barbarossa, the German invasion of the Soviet Union. Twenty to thirty aircrews had been picked to drop SD–2s and SD–10s (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. It was reported Kampgeschwader (Fighter Squadron) 51 had lost fifteen aircraft due to accidents with the SD–2s, nearly half of the total Luftwaffe losses that day.10

The last recorded death from a German butterfly bomb in England occurred on 27 November 1956, over eleven years after the end of the war: Flight Lt. Herbert Denning of the RAF was examining an SD–2 at the “Upminster Bomb Cemetery” (some remote sandpits situated East of RAF Hornchurch, where unexploded ordnance disposal (UXB) experimentation operations and research work took place) when the SD–2 device suddenly detonated. Denning died of shrapnel and blast injuries at Oldchurch Hospital the same day.11 FIG 6. German SD–2 in Full Deployed configuration Courtesy of Dave Birkin.

FIG 7. German SD–2, full deployed configuration. Note triangle wings in use

FIG 5. Butterfly Bomb deployment sequence identical for both U.S. and German munitions. Courtesy of Dave Birkin.

Courtesy of Dave Birkin.

On the island of Malta in 1981, Paul Gauci, a forty-oneyear-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. The latest find of such a bomb was on 28 October 2009, by an eleven-year-old boy in a secluded valley close to a heavily bombed airfield. This bomb was safely detonated on-site by the Armed Forces of Malta.12

The SD–2 Butterfly Bomblet would be fitted with one of three fuzes, which were made of aluminum and stamped with the model type surrounded by a circle. All were factory installed and set: (1) impact or air burst, (2) long delay (5–30 minutes), and (3) antihandling. The bomblet has a lethal radius of up to seventy yards.13 Dopp. Z. 41 or 41AZ fuze—has an external selector switch with two settings. The Z or “Zeit” (time) setting will detonate the bomb in the air, approximately five seconds after being armed. The AZ or Aufschlagzünder (impact) setting triggers detonation when the bomb hits the ground. The fuze is armed if four 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. L.Zt.Z 67 fuze—or Langzeitzünder (long time delay fuze). The time of detonation can be set between five and thirty minutes, in five minute increments, 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. Zünder 70A or B fuze—anti-handling (i.e. booby-

FIGs 8 & 9. German SD–2 in full deployed configuration (left) and closed/shipping configuration (right). Bomblet is safe. Courtesy of the Imperial War Museum © IWM (MUN 2447).

FIG 12. SD–2 as it would sometimes become entangled with trees, vegetation or buildings. Courtesy of Dave Birkin.

FIG 13. Top view of German Dopp. Z–41 fuze. Note selector switch with AZ (impact) and ZEIT (time). Courtesy of Dave Birkin.

FIG 10. Butterfly Bomblet as it would appear upon landing, armed and functioning if delay or disturbance fuzed, dud fired if impact fuzes. Courtesy of Dave Birkin.

FIG 11. Another view of German SD–2 upon landing. Note difficulty in observing type fuzed employed. Courtesy of the Imperial War Museum © IWM (MUN 2447).

FIG 14. Various color schemes used on German manufactured SD–2s, others may exist but as of now no verifiable information has been found. Authors notes, combined with assistance from Dave Birkin. 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.14

Butterfly bombs were usually found painted either straw yellow (desert camouflage, or if fitted with the Dopp Z (41) or (41) A fuze), dark green or gray. The German technical reports show the following colors used as standard.

Red Oxide—Normally associated to training use (bomb omitted smoke) Field Grey—A lighter version of the normal dark green & sometimes seen on World War II German gas mask containers Dark Green—No identification markings Dark Green—With yellow identification band on drogues’ only (sometimes hastily brush applied) Dark Green—With yellow identification band and red band on wings and drogues (red denoting “SD”) Yellow—over-all yellow with red bands on wings. Two variations of yellow shade have been identified from original examples; one quite bright, another of a more golden/dark yellow. 15

The American Version

The United States manufactured a copy of the SD–2. It was widely used in the second half of World War II, the Korean War, and Vietnam War. After technical ordnance evaluations it was designated the M83 fragmentation bomb. The four-pound fragmentation bomb was used in the U.S. M28 100 lb. (preloaded) and M29 500 lb. cluster bomb (field loaded).16

FIG 15. Portion of technical drawing from U.S. Army Ordnance Development 1944 for U.S. M–83 four-pound fragmentation bomb. U.S. Army Ordnance Archives.

This U.S. made M83 antipersonnel fragmentation bomb (now known as a submunition) entered active use in the middle 1940s and afterwards. Picatinny Arsenal was the main developer for the United States. It is an almost identical copy of the infamous German SD–2 Splitterbombe (“Splinter Bomb”), commonly known to the Allies as the “Butterfly Bomb,” both bombs had this nickname attached to itself. Very few characteristics differ between these two munitions.17

The M29 cluster bomb, a 500-pound cluster bomb used by the United States Army Air Force (later United States Air Force), Navy, and Marine Corps aircraft beginning

in World War II, against troops, airfield, unarmored vehicles, and artillery positions, as well as an area denial munition. The weapon contained ninety four-pound M83 fragmentation submunitions, in nine ten-bomb “wafers.” The M28 was a one hundred-pound equivalent of the M29 containing twenty-four bomblets. This bomb was shipped from the factory preloaded. All contained a mixed load of different fuze types with intermixed fuze settings.

Both cluster-bombs were fitted with a mechanical time fuze that could be set to open the cluster at a preselected time between five and ninety seconds by triggering a burster charge. The case sides and ends sprung open, allowing the bomblets to be freed and fall out. The bomblets spring loaded cup shaped wings opened; the canted sides imparted a counterclockwise rotation of the bomblet, while helping to retard the fall as well, the wings rotated to arm the fuze.18

U.S. Fuzing

There were three fuzes available for the U.S. Butterfly bomb: M129, M130, and M131. The fuzes were armed after 3½ (¼-inch of travel) revolutions of the arming cable assembly, this is rotated by the deployed drogue wings. M129 Bomb Fuze—designed to function approximately five seconds after the cluster opens (aerial burst) or upon impact. The setting switch on top of the fuze body, designating “ground or air,” can be set for the desired functioning. The fuze is set in the factory and the wafers are not to be disassembled in the field to alter the settings.

M130 Bomb Fuze—a mechanical time fuze which can be

FIG 17. U.S. Air Force M–29 cluster bomb unit after accidental jettisoning from aircraft. Note now armed Butterfly Bombs around cluster, circa 1966. Courtesy the author.

FIG 18. Ordnance Field Guide, Vol II, Revised September 1945 (Harrisburg, PA: Military Service Publishing Company, 1946).

FIG 16. Exploded view of inert U.S. M–83 four-pound bomblet. Courtesy of the author. FIG 19. Dud U.S. M–83 in Laos found in 1993 during ordnance clearance operations to restore farming land. Courtesy the author. set to function at various times up to thirty minutes. The time setting is predetermined at the factory and cannot be adjusted in the field.

M131 Bomb Fuze—an antidisturbance fuze which arms upon impact and will be functioned by vibrations or disturbances in its near vicinity.19

The U.S. manual warns that, “Use of the M131 (antihandling) fuze is not recommended in areas that are expected to be occupied by friendly forces as they constitute a potential booby-trap hazard.”20

Conclusion

Some references have been made by foreign historians the German Butterfly Bomb holds the distinction of being the “first scatterable mine,” followed by the Italian Thermos Bomb; however, reading of the German technical

FIG 20. German Butterfly Bomb warning sign distributed in Great Britain during World War II. Courtesy of the Imperial War Museum © IWM (MUN 2447 manuals does not give this ordnance item that deployment usage. Neither did the design outline of intended usage. One example references German General Rommel having staff officers fly over areas prior to deploying these bombs; they were used to supplement hand laid minefields. Never were they classified as scatterable mines or looked upon as such. It would not be proper to apply late twentieth century tactical thinking to items used prior to the advent of such. Notwithstanding this point, the German SD–2 was the first submunition designed, deployed, and updated for use exactly as today’s cluster munitions are designed for. As the grandfather of cluster munitions, the “Butterfly” Bomb has a firm claim to this distinction, and as an outstanding idea it was duplicated by the United States to even greater usage.

Notes

1. Engineering Technical Summery, Picatinny Arsenal, U.S.

Ordnance Corps, U.S. Army Data Sheet 104–44, 1944. 2. U.S. Naval EOD School, Notes from Air Ordnance Division,

Submunitions, author’s collection, March 1979. 3. U.S. Navy, NAVORD OP 1666, German Explosive Ordnance, 11

June 1946, 32–34. 4. Jonathan Garraway, ”Operation Barbarossa,” Fly Past, no. 359 FIG 21. German Luftwaffe personnel posting danger sign in France during World War II. Courtesy of Dave Birkin.

(June 2001): 70. 5. Royal Army, Department of Unexploded Bomb Division, Bulletin 306, 8/43, Lecture Notes on Butterfly Bombs, sect III, (8). 6. U.S. Navy, NAVORD OP 1666, German Explosive Ordnance, 11

June 1956, 30–31. 7. Robert Forsyth, Me–262 Bomber and Reconnaissance Units (Oxford, UK: Osprey Publishing, 2012), 31. 8. U.S. Army, Army Technical Manual, TM9–1985–2, March 1953, 42–44. 9. James I. Rogers, (21 June 2013), “Remembering the terror the

Luftwaffe’s butterfly bombs brought to the North,” The Guardian, retrieved 9 February 2016. 10. Maj. Lonnie O. Ratley III, “A Lesson of History: The Luftwaffe and

Barbarossa,” Air University Review (March-April 1983). 11. web.archive.org/web/20120304162916, www.rafbdhistory.co.uk/ new_page_6.htm. Archived from the original on 4 March 2012, retrieved 14 May 2012. 12. “Boy Finds Lethal WWII Bomb in Qormi Valley,” Times of Malta, 29 October 2009. 13. U.S. Navy, NAVORD OP 1666, German Explosive Ordnance, 11

June 1956, 36–39. 14. Ibid. 32–33. 15. U.S. Army, Army Technical Manual, TM9–1985–2, March 1953, 44–45. 16. U.S. Navy, Bureau of Ordnance Circular Letter, AV14–44, 31 May 1944. 17. Engineering Technical Summary, Picatinny Arsenal, U.S.

Ordnance Corps, U.S. Army Data Sheet 104–44, 1944. 18. Ordnance Field Guide, Vol II, Revised September 1945 (Harrisburg

PA: Military Service Publishing Company, 1946), 410–413. 19. Ibid. 20. U.S. Navy, Bureau of Ordnance Circular Letter, AV14–44, 31 May 1944.