Monday, March 9, 2015

SD 2 Schmetterling

The air-delivered German SD 2 Schmetterling (butterfly) cluster bomb appears to be the first purpose-built scatterable landmine laying system employed in combat. It was first used against the Poles in September 1939. The Germans used air-burst/impact (SD 2A (41) and SD 2B (41) A), anti-disturbance (SD 2B (70) B, with selectable self-destruct times from four to thirty hours) and time-delay (SD 2B (67) with a 5-30 minute delay) fuzes with their SD-2s. “All three types of fuze were used indiscriminately in the same container load.” The Luftwaffe deployed the Schmetterling from low-altitude as submunitions carried in the AB 23 (23 SD 2s), AB 70-3 (22 SD 2s), the AB 250-1 (96 SD 2s), the AB 250-2 (144 SD 2s), the AB 250-3 (108 SD 2s), the Mk 500 (6 SD 2s), and the AB 24t (24 SD 2s). By May 1941, fifteen different groups of the Luftwaffe had the specially modified aircraft (five of Ju-88s, three of Do-17s, four of Me-109s, or three of Ju-87s) required for emplacing the SD 2. Each modified Ju-88 or Do-17 could dispense 360 SD 2s, while the modified Me-109 or Ju-87 could dispense 96 of the SD 2s. The Germans planned to modify two groups of Me-110s (each capable of dispensing 96 SD 2s) beginning in July of 1941. “As long as fronts remained fluid, these bombs proved highly effective although unfortunately in short supply.” However, effective antiaircraft defenses could limit the ability of the Luftwaffe to employ them. Although the Germans had several other types of cluster bombs (e.g. SD 1, SB 3, SD 4 (with a shape charge), and SD 10), none of these were fuzed to function as a landmine and these were not used in quantities comparable to that seen of the SD 2. In addition, the German ABB 500 container could carry 2,200 “crow’s feet” (caltrops). Interestingly, these early cluster bombs (with anti-disturbance fuzes) were not officially called “mines” until the Vietnam War. Perhaps the vocabulary with respect to these devices developed in this fashion because the air-scattered landmine evolved from a cluster bomb as well as the fact that these rested on the surface of the ground and were not buried as landmines were.

Royal Engineer Major Arthur Hartley, who performed EOD work during the Battle of Britain, noted that in 1942 one of the principal developments was the increased use of butterfly bombs by the Germans. “Butterfly bombs had already made their appearance as an occasional and minor constituent of the dose in large raids, but it was only now that they began to be regularly employed. As the year wore on the reports on nearly every raid recorded their use and the casualties they had inflicted. These little devices, each weighing two kilos (about 4 ½ lb.), were launched from the bomber in a sheet metal container which usually was designed to hold twenty-three or twenty-four… Once armed the butterfly bomb could not be disarmed again. The only method of disposal was demolition in situ… Since their thick-walled cases gave powerful fragmentation and made them very effective anti-personnel weapons, great care had to be exercised in accounting for them. Several officers and N.C.O.’s were killed at different times not by the bomb they were engaged in demolishing, but by the sympathetic explosion of another lying undiscovered some little distance away. Thus it was usually necessary to account for every bomb in a batch before demolition could start; something easier said than done, for though recovery of the original container would indicate the number scattered over a particular spot, these hideous little mobile booby-traps had an extraordinary aptitude for hiding themselves in garden hedges, long grass, and a thousand other places.” Beginning with a saturation raid on east London and Essex, the Luftwaffe began employing the SD 2 “very effectively.” The heaviest use of them against an urban area occurred on 13 June on Grimsby and Cleethorpes when the Luftwaffe dropped “great numbers of the sensitive, post-impact booby-trap type” (nevertheless, the majority of SD-2s had time-delay fuzes) and brought both towns almost to a standstill. During this time a single company (No. 3) cleared 1,500 butterfly bombs. “Considering how successfully this raid had dislocated movement and production, it was naturally feared that this would be a prelude to a series… But the expected raids never materialized… There is little doubt that this was at least partly due to the great improvement in security arrangements. In spite of the scale of the operation it seems that the Germans never realized the full measure of the bomb’s potentialities” against civilian targets. 

Unexploded Bomb, A History of Bomb Disposal, by Arthur Hartley, W. W. Norton & Company, New York, 1958, page 213. The failure to use SD-2s against Operation Overlord may stem from the fact that the Luftwaffe had higher priority tasks (such as defending their homeland and fighting the Russians) or the fact that they may have exhausted their supply of SD-2s and never replenished it.

The German SD 2B Schmetterling was also used effectively against the Russians during Operation Barbarossa, beginning in June 1941. The SD 2B, fitted with the (70)A chemical/mechanical long delay and anti-disturbance fuze with a selectable self-destruct time from four to thirty hours, constitutes one of the earliest self-destructing scatterable mines. Nevertheless, the Germans forbade the use of SD 2s with anti-disturbance fuzes against retreating opponents due to the hazard to friendly forces. The SD 2 with anti-disturbance fuze was intended for use against targets behind enemy lines for “harassing effect” only. The Germans “at least understood the value of these little bombs against military formations. Colonel S. M. Lovell, a member of a British military mission to the U.S.S.R. who had the duty of advising on bomb disposal matters, had found that the Russians attached the greatest importance to the butterfly bomb… Used in high concentrations it had cost the Red Army great numbers of casualties and effectively held up the movement of formations. Russian soldiers had been reduced to detonating bombs by rifle fire, a method certain to cause casualties since the butterfly’s fragmentation range was a hundred yards, at which distance it presented, at best, a poor target-and the rifleman was bound to have his face toward the bomb.”

During the campaign in North Africa, Field Marshal Rommel employed scatterable mines. On 5 April 1941 Major Heymer, one of his staff officers, “had been sent on a mission with two aircraft to mine the tracks east of Mechili”, presumably to further isolate this post in preparation for an attack. During the period August to September 1942, the Luftwaffe dropped “many thousands” of ‘butterflies’ just in the 2nd New Zealand Division area, but caused few casualties. At the end of October during Operation Lightfoot, German aircraft dropped SD 2s on the 2nd New Zealand Division’s artillery, apparently in one of the first attempts to re-seed a minefield that the British 8th Army had breached earlier in the battle. The Luftwaffe also employed SD 2s in Tunisia and Italy.

During the difficult days at Anzio in February 1944, “The enemy used increasingly large percentage of anti-personnel ‘butterfly’ bombs in his night attacks, which caused casualties throughout the beachhead.” Soldiers serving at Anzio referred to the German pilots who regularly dropped strings of antipersonnel bombs that crackled as they dispersed, Popcorn Pete. These landed in every corner of the beachhead. “Between January 22 and March 12, antipersonnel bombs dropped from German planes killed 40 men and wounded 343.” On 7 February, a German plane under attack by British Spitfires jettisoned its cluster bombs. In the tightly backed beachhead, these fell on the 95th Evacuation Hospital, killing 28 and wounding 64. “Two raids on March 17 killed 16 and wounded 100.”

During preparations for the invasion of Europe, the British were deeply concerned about the use of butterfly bombs against the marshalling and embarkation areas. “No such attacks were made either on the ports and their surroundings or on the close-packed Caen Peninsula (in Normandy). The neglect of such an obvious, effective and economical weapon at such a time was never to the author’s knowledge, been satisfactorily explained.” Impressed by the effectiveness of the SD 2, the US attempted to copy it as the M83. After numerous tests Aberdeen Proving Grounds through 1944, the US Army standardized the cluster bomb with three different types of fuzes (M129 impact, M130 Clockwork long delay and M131 Anti-Disturbance) and two different sizes of container (the M15 and M16 cluster adapters, holding 24 and 90 M83 respectively), with testing continuing through the summer of 1945. However, “Fuze failure and the tendency of the cluster to open too soon after release sometimes made experience with the bomb in the field discouraging.” Consequently, the M83 did not see significant action during WWII. However, the US did employ it in Korea and Vietnam.

Italy soon followed the Germans with their air-scattered “Thermos Bombs” (also called the 4-AR Anti-Personnel Bomb Manzolini). Like the SD 2, the thermos bombs also came with anti-disturbance/time-delay fuzing (but apparently no impact fuze). The time-delay feature of the Manzolini Fuze causes the Thermos bomb to self-destruct between 60 to 80 hours after its deployment. Twenty-four of the Thermos Bombs could be carried as a submunition in an aircraft dropped Bomb Container. They made their combat debut against the 4th Indian Division under the British in Egypt on 14 September 1940. “A group of Italian bombers strewed the Baqqush and Naghamish areas with thermos flasks and shaving-stick antipersonnel bombs – vicious little contrivances which exploded when moved. An unwary officer and four other ranks were killed in picking up these missiles. Rough harrows towed by carriers were devised to deal with them but for some time natural curiosity took its toll and these booby traps retained considerable nuisance value.” During the subsequent campaign in North Africa, the Italians employed them fairly extensive numbers. For example, the Italians also dropped Thermos bombs on the 6th Australian Division as it invested Bardia in January 1941 and to cover their retreat along the trails west of Tobruk in February. However, on 4 April 1941 as Rommel directed an advance by his 5th Light Division (which later became famous as the 21st Panzer Division) along the Trigh el Abd toward the Libyan coast between Derna and Tobruk, the remaining Thermos bombs posed something of a problem. An Italian general anxiously pointed out to Rommel, “that trail is a death track! We saturated it with Thermos mines two months ago during our retreat.” Rommel ignored his objections. Consequently, “Hefty explosions suddenly lit the sky as the first Thermos mines were hit. An ammunition truck erupted in a ball of fire, illuminating the desert for miles around.” The Italians also used them during the siege of Tobruk in April and May. During Operation Crusader in November 1941, the 6th New Zealand Engineer Company had “an unpleasant experience by camping in a nest of thermos bombs, one of which advertised its presence by exploding under Lieutenant McFarland’s truck. ‘We walked on tip-toe all night; marked off 20-odd more without further explosion, then moved out and set them off with rifle-fire. MacFarland wasn’t hurt, but the truck was very battered underneath.’” Although early scatterable mines, such as the “Butterfly” and the “Thermos Mines” laid on the surface of the desert with contact-fuzes (and hence could be easily avoided), they routinely caused casualties among the unwary.

However, there seems to be little information on British use of their air-scatterable mines, called the Mk II fragmentation bomb. It was fitted with long-delay (factory-set up to 6 hours on Tail Fuze No. 880) and/or anti-disturbance fuzes (tail fuzes No. 881 and No. 883). Field Marshal Rommel makes reference to them (or something similar). Describing actions on the night of 2 September during his failed attack at the Battle for Alam Halfa, “the Afrika Korps, part of the Italian armoured divisions and the 90th Light Division were once more subjected to non-stop pounding by powerful British bomber formations… vast quantities of H.E. and fragmentation bombs, even some landmines, dropped into the territory occupied by my troops… Hundreds of our vehicles were destroyed or damaged.” The British “Cluster Projectile 500-lb. No. 7 Mk I” could carry 56 Mk II fragmentation bombs.

During the Korean War, beginning on 31 May 1951, “In an effort to establish roadblocks, 3d Bombardment Wing B-26’s strewed M-83 butterfly bombs at prebriefed choke points on the enemy’s main supply routes.” The US Air Force used M15 and M16 “cluster adapters” to carry the M83, each holding 24 or 90 munitions respectively. Apparently, a B26 Intruder (which frequently dropped the M83s in Korea), could carry up to fourteen M16 Cluster Adapters (a total of 1260 M83s). As finally fielded, the US copies of the German SD 2 came fitted with one of three fuze options: Impact (M129), Clockwork long delay (M130), or Anti-Disturbance (M131). The US Air Force continued to refine its mining tactics. Beginning in late August 1952, “At last light, fighter-bombers cratered selected highway intersections, and at first darkness two intruder B-26’s dropped butterfly bombs and delayed action ordnance on adjacent feeder and secondary roads. Two major and two minor roadblocks were usually established each night on the highway net south of Pyongyang and on the lateral road to Wonsan. Forty-five minutes following the establishment of a major roadblock, and at such intervals throughout the night, individual B-26 intruders flew armed reconnaissance missions over the isolated roads, attacking stalled vehicles with … fragmentation bombs. The new tactics worked well. Up to 25 vehicles were frequently found and destroyed within a roadblock area, and the September destruction claims rose to 2,167 vehicles.” Toward the cease-fire, Communist prisoners “stated that they had been highly demoralized by the butterfly bombs which they stumbled on in the dark.”

However, ineffective (or non-existent) reporting of the locations where M83 had been dropped could cause problems for friendly ground forces. For example, “In the Hongch'on area, the [1st] cavalry division stood fast along the Hongch'on River on the 15th [of March 1951] to wait for the marines to come up on its right. Strong enemy positions on a ridge due east of Hongch'on stalled the marines in that area, but at the far left of the Marine zone the town itself fell to the 1st Battalion, 7th Marines, at noon. A motorized patrol, first to enter, found the town ruined and undefended. On the return trip, following an explosion that damaged a truck, the patrol discovered that Far East Air Forces bombers had liberally sprinkled the eastern half of the town with small [M83 butterfly] bombs set to explode when disturbed. A company of Marine engineers began the uncomfortable task of clearing these explosives while the 1st Battalion passed through and occupied high round immediately northeast of town.”

I would be very interested in more information on these devices. How many were produced? Who invented/manufactured them? Any other exmplaes of their use in combat?

References and notes:
1. German Explosive Ordnance (Bombs, Fuzes, Rockets, Land Mines, Grenades, and Igniters), TM 9-1985-2, Departments of the Army and the Air Force, Washington, D.C., March 1953, pages 33-42, 95-108, 132-134, 187. Unexploded Bomb, A History of Bomb Disposal, by Arthur Hartley, W. W. Norton & Company, New York, 1958, pages 132-134. “Those [SD-2s] equipped with the sensitive after-impact fuzes would often detonate from the shock caused by another bomb of the batch exploding in the vicinity.” German Air Force Operations in Support of the Army, by Paul Deichmann, USAF Historical Studies: No. 163, Arno Press, New York, pages 43-44.

2. British Explosive Ordnance, TM 9-1985-1, Department of the Army, July 1952, pages 5, 6, 187-189, 201-203, 208-210, 220-224, 229-233, 236-237, 258-260, 279-281, 285-289; and Japanese Explosive Ordnance, TM 9-1985-4, Department of the Army, March 1952, pages 144-154, 179-182. Of the major combatants in World War II, only the Soviet Union appears to have not developed some form of scatterable landmine. See Soviet Explosive Ordnance (WWII) (Russische Munition), DTIC # ADB031828, January 1944, particularly page 4.

3. The Rommel Papers, edited by Liddell Hart, Harcourt, Brace, & World, New York, 1953, pages 113-114. 2nd New Zealand Divisional Artillery, by W. E. Murphy, Historical Publications Branch, Department of Internal Affairs, Wellington, New Zealand, 1967, pages 397, 401. See The Turning Point, With the N. Z. Engineers at El Alamein, pages 181-182. See also German Air Force Operations in Support of the Army, by Paul Deichmann, USAF Historical Study No. 163, Arno Press, New York, 1962, page 43. However, this study is mistaken in one respect, the SD-2 (not the SD-1) was subsequently copied by the Americans. See also German Explosive Ordnance (Bombs, Fuzes, Rockets, Land Mines, Grenades, and Igniters), TM 9-1985-2, Departments of the Army and the Air Force, Washington, D.C., March 1953, pages 34-35, 97-98, 100-110. For the efforts of a Major Reid of the Royal New Zealand Engineers to disassemble a German butterfly mine in the summer of 1942, see The Turning Point, With the N. Z. Engineers at El Alamein, pages 112-113. No information has been found to date that discusses the methods used by the Axis to employ or mark the locations of their scatterable mines (however, maps are extant which show the general areas into which they were dropped). In the German case, it appears, considering the small number available, that the ‘doctrine’ for their use was left to the discretion of either the senior ground commander or his air force staff officer. In North Africa, at least, the Axis’ scatterable mines do not appear to have been well integrated with any of the ground tactical operations. North Africa, 1940-1943, Landmine and Countermine Warfare, Engineer Agency for Resources Inventories, Washington, D.C., June 1972, pages15, 20, 30 50, & 51.

4. North Africa, 1940-1943, Landmine and Countermine Warfare, page 15. Luftwaffe Handbook, 1939-1945, by Alfred Price, Charles Scribner’s Son’s, New York, New York, 1997, page 42.

5. Anzio Beachhead, 22 January – 25 May 1944, CMH Pub 100-10, US Army Center of Military History, Washington, D. C., 1948, pages 52-53. A photo in this book shows part of a AB 500-1 cluster bomb. Anzio, The Gamble that Failed, by Martin Blumenson, Dell Publishing Company, New York, 1963, pages 145, 147.

6. Unexploded Bomb, A History of Bomb Disposal, by Arthur Hartley, W. W. Norton & Company, New York, 1958, page 213. The failure to use SD-2s against Operation Overlord may stem from the fact that the Luftwaffe had higher priority tasks (such as defending their homeland and fighting the Russians) or the fact that they may have exhausted their supply of SD-2s and never replenished it.

7. The Ordnance Department: Planning Munitions for War, by Constance McLaughlin Green, Harry C. Thomson, and Peter C. Roots, Office of the Chief of Military History, Department of the Army, Washington, D. C., 1955, page 461.

8. The 1st Cavalry Division and Their 8th Engineers in Korea, edited by Frank Armstrong, Bull Run of Vermont, South Burlington, Vermont, 1993, page 180.

9. Viet Cong Boobytraps, Mines, and Mine Warfare Techniques, TC 5-31, Headquarters, Department of the Army, December 1969, page 2-11.

10. North Africa, 1940-1943, Landmine and Countermine Warfare, Engineer Agency for Resources Inventories, Washington, D. C., June 1972, pages 15 (based on Fourth Indian Division, by Stevens, Constable, London, 1955, pages 37-38), 20, 30, 44, 51. The claims that this was the first use of scatterable mines is incorrect, nor does it appear the Italian design influenced the German development of the SD 2. For technical data, see Italian and French Explosive Ordnance, TM 9-1985-6, Departments of the Army and the Air Force, Washington, D. C., March 1953, pages 3, 24-25, 59-60). A Corporal Ted Madigan (a New Zealand sapper) and a Major ‘Waddy’ Wadison, Royal Engineers, disassembled a dud thermos mine in late 1940 and learned how it worked. See New Zealand Engineers, Middle East, page 16. Trail of the Fox, by David Irving, Clark, Irvin and Company, Toronto, 1977, pages 76-77. Die 5. (lei.)/21. Panzer-Division in Nordafrika, 1941-1943, by Heinz-Dietrich Aberger, Preußischer Militär-Verlag, Reutlingen, 1994, pages 44-45.

11. The United States Air Force in Korea, 1950-1953, by Robert F. Futrell, Office of Air Force History, US Air Force, Washington, D.C., 1983, pages 131, 132, 165, 302, 327, 328. However, it proved next “next to impossible to evaluate the success or failure” of the delayed-action mines against hostile supply lines, consequently, “Bomber Command soon rejected this tactic.” Brooks filed his patent application on 19 October 1942 to improve the 3,000 year old design of the caltrop, however, it is uncertain if the caltrop dropped by the US in Korea was related to this patent in anyway. Most US and European patents are available online at ,however, for older patents, one must know the number or be prepared to search by “patent category.”

12. Ebb And Flow, November 1950-July 1951, by Billy C. Mossman, United States Army In The Korean War, Center Of Military History United States Army, Washington, D.C., 1990 reprint, page 328, available online at: .

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