Fragmentation Bombs, WWII Tactical and Technical Trends, No. 29, July 15, 1943 (Lone Sentry)

Certain characteristics of fragmentation bombs are described in the following article, reprinted from issue No. 12 of AFGIB (Air Forces General Information Bulletin). Included in the summary is a reference to a few types of Axis bombs in this category, particularly those of a "combination" character.

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In the category of "fragmentation" bombs are included certain bombs of small size designed for destructive effect on personnel, animals, and light materiel targets such as motor transport, and aircraft on the ground or in flight. Bombs of this class are generally less than 100 pounds in total weight, and are often termed antipersonnel bombs.

Whereas general-purpose demolition bombs depend for destructive effect primarily on their violence of detonation, with fragmentation a secondary consideration, fragmentation bombs depend primarily on the projection at high velocity of bomb-body fragments. The design of the bomb-body, and the charge/weight ratio, are determined with this end in view. Thus, with our demolition bombs the high explosive charge may approximate 50% of the total bomb weight; where with fragmentation bombs it may approximate only 15%...

Fragmentation bombs may be dropped singly or in clusters, bound or held together during a portion of their fall and then released, or in containers which operate in a similar manner. The purpose of dropping in clusters or containers is to ensure a closer concentration of bombs dropped from high levels, since bombs dropped singly would tend to disperse considerably during their fall. Such clusters or containers are generally provided with either an explosive cartridge or a spring-loaded mechanical device, which functions after a predetermined period to break open the cluster or container and free the bombs...

The normal fuzing is, therefore, with instantaneous impact-type nose fuze. However, time (delay) fuzing may be necessary if the bombs are to be dropped from low level, in order that the aircraft may be beyond the danger space when the bomb explodes.

In dropping from low level, the disadvantage of time fuzing is somewhat counterbalanced by the fact that the bomb is more apt to ricochet and come to rest on the ground surface, and less liable to bury itself, than if dropped from higher levels. However, low-level drop with instantaneous fuzing has been made feasible by the provision of a chute attachment for the bomb. This greatly retards the flight of the bomb, allowing the aircraft to get beyond the danger zone before the bomb reaches the ground and detonates. Release of this bomb is possible at 100 feet, and lower if tactically required.

In addition to normal types of fragmentation bombs, the Axis nations have employed some which are unusual in design, or of a "combination" character. A few of these are noted below.

The German SD* 2-kilogram "butterfly" bomb differs markedly in appearance from ordinary types. The small drum-shaped body is enclosed in a hinged shell of thin metal which opens in flight and acts as a metal braking drogue similar to a parachute attachment. The usual fuze allows either instantaneous burst or time delayed action of 3 to 5 seconds. It is thought that in some cases a disturbance-operated (antihandling) fuze may be fitted, of a type such that bombs which have come to rest on the ground are thereafter exploded by the least jar or movement.

The Italian 4 A.R.** (thermos) bomb is normally equipped with an anti-disturbance fuze which functions if the bomb is moved or jarred after coming to rest on the ground. This bomb resembles a thermos bottle in general size and shape, and may attract the curious to pick it up, kick it, or otherwise disturb it -- to their extreme misfortune. It partakes of the nature of a booby trap, though it is distributed by airplanes.

It may be pointed out that antipersonnel bombs equipped with these anti-handling fuzes are not only fatal to the unwary -- they are annoying and difficult to dispose of even when their nature is thoroughly understood. Thus they serve to hamper operations on ground where they have been dropped.

The Japanese 50-kilogram phosphorous pellet bomb is a dual-purpose bomb combining antipersonnel and incendiary effects. On detonation, the steel bomb-body fragments are projected at high velocity in a flat cone, and numerous phosphorous-impregnated pellets are scattered. This bomb is described as being quite effective for antipersonnel uses.

The German 2.2-kilogram I.B.E.N. (incendiary bomb with explosive nose) similarly combines incendiary and antipersonnel effect; but this bomb is primarily an incendiary, with the high-explosive and antipersonnel component added to hamper and delay fire fighters. The antipersonnel component may break off and come to rest at a distance from the incendiary portion of the bomb, yet function nevertheless. It explodes from 1 to 7 minutes (approximate time) after the incendiary portion has functioned. The delay is unpredictable, and varies with individual bombs.

During the Japanese raid on Rangoon, 23 December 1941, some ten or a dozen antipersonnel bombs fell in an open space of about 150 by 250 yards, which was laced with slit trenches. But the people were on top of the trenches and even ran out of them, with the result that 250 were killed on the spot in a few minutes. The wounds were generally terrible leg and stomach injuries. The most fatal zone was within 50 to 60 yards of the burst, but some individuals were killed up to 300 yards away.

Had these people remained in the trenches, even without overhead cover, the casualties would have been negligible by comparison. The slit trench or foxhole provides excellent protection against small fragmentation bombs. Wherever they may be expected, a little "digging in" will pay dividends.

Corresponding destruction has been achieved on aircraft or motor transport caught undispersed in the open.

While the SD 2 "butterfly" bomb and the 4 A.R. "thermos" bomb are especially to be avoided, unexploded specimens of any fragmentation bomb should be given a wide berth. Failure of the fuze to function normally on impact may nevertheless leave the bomb in a highly sensitive condition; and the disposal of such "duds" can be safely undertaken only by specially trained personnel.

*[SD is the designation for a bomb with a thick casing, which achieves its effect chiefly by fragmentation.]
**[Armamento Ritardato - delayed action.]