An anti-handling device is an attachment to or integral part of a landmine or other munition e.g. some fuze types found in general purpose air-dropped bombs, cluster bombs and sea mines. It is specifically designed to prevent tampering. When the protected device is disturbed it detonates, killing or injuring anyone within the blast area. There is a strong functional overlap of booby traps and anti-handling devices: a munition with an anti-handling device fitted has, for all intents and purposes, been booby-trapped.
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Anti-handling devices serve two military purposes:
Anti-handling devices greatly increase the impact of munitions on civilian populations in the areas in which they are used because their mechanisms are so easily triggered. An unexploded bomb may or may not detonate if it is lifted or overturned, whereas an anti-tank mine with an anti-handling device fitted is almost guaranteed to detonate if it is lifted/overturned, because it is specifically designed to do so. Additionally, munitions fitted with anti-handling devices increase the difficulty and cost of post-conflict clearing operations, due to the inherent dangers of attempting to render them safe.
Not all munitions will have an anti-handling device fitted or enabled. Perhaps one in ten antitank mines in a large defensive minefield will have boobytrap firing devices screwed into their secondary fuze wells. Even so, deminers and EOD personnel are forced to assume that all items they encounter may have been boobytrapped, and must therefore take extra precautions. This has the effect of significantly slowing down the clearance process, even allowing for the fact that the anti-tank mines in question may be interspersed with various different types of minimum metal antipersonnel mines such as the VS-50 or TS-50, some of which can also have anti-handling features.
Technology to incorporate sophisticated anti-handling mechanisms in fuzes has existed since at least 1940 e.g. the Luftwaffe's ZUS-40 anti-removal fuze (of which 3 slightly different versions existed)[1] which was used during the London Blitz and elsewhere.[2][3] ZUS-40s were designed to fit underneath most Luftwaffe bomb fuzes. When a delayed-action bomb containing a ZUS-40 was dropped on a target, the massive jolt after it hit the ground freed a ball-bearing inside the ZUS-40, thereby arming a spring-loaded firing pin. However, so long as the main bomb fuze remained inside its fuze well, the cocked firing pin in the ZUS-40 was prevented from springing forward. ZUS-40s were often fitted underneath a type 17 clockwork long delay fuze, which gave up to 72 hours delayed detonation. Rendering safe a type 17 fuze was normally a simple and straightforward process i.e. unscrew the fuze locking ring, remove the fuze from its pocket in the side of the bomb and unscrew the gaine. However, fitting a ZUS-40 underneath a type 17 fuze made the render-safe process much more complicated and dangerous. Removing the main time-delay fuze more than 2 cms from its fuze pocket (without neutralising the anti-handling device underneath) automatically released the cocked firing pin inside the ZUS-40, which sprang forward to strike a large percussion cap, thereby causing detonation of the bomb and the death of anyone kneeling beside it. Because the ZUS-40 was designed to be concealed underneath a conventional bomb fuze, it was very difficult to know whether a particular bomb was fitted with an anti-handling device or not. In any case, many electrically-fired German bomb fuzes (which could be fitted above a ZUS-40) already had a tiny pendulum based "trembler" device inside them, which closed the circuit and triggered detonation if the bomb was subjected to rough handling. Some German anti-handling fuzes were even more sophisticated and therefore particularly dangerous to EOD personnel e.g. the type 50 and 50BY fuzes. These were normally fitted to 250/500 kg bombs and contained two mercury tilt switches which detected movement across vertical and horizontal axes. The fuzes fully armed themselves approximately 30 seconds after hitting the ground. Subsequently, if the bomb was moved in any way, the mercury switch completed an electrical circuit and triggered detonation. To complicate matters still further, German bombs could have two separate fuze pockets fitted, with different fuze types screwed into each one. As a result, one bomb could incorporate two separate anti-handling devices working independently of each other e.g. a type 17 clockwork fuze with a ZUS-40 hidden underneath it screwed into one fuze pocket, and a type 50BY in the other. Although the designs of these anti-handling fuzes varied, all were specifically designed to kill bomb disposal personnel who had the task of rendering them safe.
Allied forces developed their own designs of anti-handling devices during World War II. For example, the American M123, M124, M125 and M131 series of long delay tail-fuzes, or the British "Number 37 Long Delay Pistol", were used in air-dropped bombs. These were primarily designed to operate as chemical long-delay fuzes, with time settings ranging between 30 minutes and 144 hours. However, they also contained anti-withdrawal mechanisms designed to kill anyone who tried to render a bomb safe: any attempt to unscrew and remove one of these long-delay fuzes from the fuze pocket of a bomb after it had been dropped would automatically trigger detonation by releasing a cocked firing pin which struck a percussion cap connected to an adjacent detonator.[4] The British nose fuze number 845 Mk 2 (used by RAF Bomber Command during World War II) operated purely in anti-disturbance mode. It contained a mercury tilt switch which triggered detonation if the bomb was moved after a 20 second arming delay, which started when the bomb hit the ground.[5]
Since then, many nations have produced munitions with fuzes which have some form of anti-handling function. Alternatively, they have produced munitions with features which make it very easy to add an anti-tamper function e.g. extra (but empty) threaded fuze wells on anti-tank landmines, into which the detonators on booby-trap firing devices (plus booster attachments) can be screwed.
US Army field manual FM 20-32 classifies four classes of anti-handling devices:
The different classes of anti-handling devices are normally created using a variety of fuzes. This is a list of the types of fuzes used as anti-handling devices: