S-mine
The German S-mine (Schrapnellmine), also known as Bouncing Betty, is the most well-known version of a class of mines known as bounding mines, which launch into the air about waist height to then explode, propelling shrapnel horizontally at lethal speeds. The S-mine was an antipersonnel landmine developed by Nazi Germany in the 1930s and used extensively by German forces during World War II. It was designed to be used in open areas and to attack unshielded infantry. Two versions were produced, designated by the year of their first production: the SMi-35 and SMi-44. There are only minor differences between the two models.
The S-mine entered production in 1935 and served as a key part of the defensive strategy of the Third Reich. Until production ceased with the defeat of Germany in 1945, Germany produced over 1.93 million S-mines. These mines were responsible for inflicting heavy casualties and slowing, or even repelling, drives into German-held territory throughout the war. The design was lethal, successful and much imitated, and remains one of the definitive weapons of World War II.
History
The first Allied forces to encounter the S-mine were French soldiers who were attempting minor probes into the coal-rich German Saar region from September 7th through 11th, 1939, during what is known as the Phony War. The S-mine alone was almost wholly responsible for turning back these French incursions. The mine's performance in the Saar region affirmed its effectiveness in the eyes of the German leadership, and prompted the United States and other countries to attempt to copy the design. After their experience, the French nicknamed the mine the silent soldier.
Nazi Germany used the S-mine heavily during the defense of its occupied territories and the German homeland during the Allied invasions of Europe and North Africa. The mines were produced in large numbers and planted liberally by defending German units. For example, the German Tenth Army deployed over 23,000 of them as part of their defense preparation during the Allied invasion of Italy. S-mines were deployed on the beaches of Normandy in preparation for the D-Day invasion, as part of a general program of heavy mining and fortification. The mines were subsequently used to defend German positions during the Battle of Normandy and in the defense of Northern France and the German border. S-mines were typically used in combination with antitank mines to resist the advances of both armor and infantry.
It was during the Allied actions in Europe that the S-mine gained its cynical nickname Bouncing Betty from American infantrymen. The S-mine had a great psychological effect on Allied forces, because of its tendency to seriously maim infantrymen's limbs or genitalia rather than killing them. In his book Mine Warfare on Land, Lt. Col. Sloan described the S-mine as "probably the most feared device encountered by Allied troops in the war."
Characteristics
The German S-mine was a steel cylinder less than 13 cm (5 inches) tall without its sensor, and only 10 cm (4 inches) in diameter. A steel rod protruding from the mine's top held the main fuse, where its trigger or sensor was attached. The SMi-35 had a central fuse, while the SMi-44 had an offset fuse. It weighed roughly 4 kg (9 pounds), with the weight depending on whether it was loaded with the lighter powdered or the heavier poured TNT.
The main charge of the mine used TNT as its explosive; the propelling charge was black powder. All triggers for the mine were designed to create a spark to set off a flammable fuse inside the device. The standard pressure sensor used a percussion cap for this purpose.
The main fuse was designed to delay the firing of the propelling charge for roughly four seconds after the mine was triggered. The explosion of the propelling charge sent the mine upwards into the air, and activated three short-delay pellets between the propelling charge and the three detonators. These short-delay pellets slowed the mine's detonation long enough for it to reach an appropriate height before exploding.
The standard pressure sensor was built to be activated if it was depressed by a weight of roughly 7 kilograms (15 pounds) or greater. This was to insure it was not detonated by wildlife or natural impacts. The tripwire adapter for the mine was a shallow Y-shaped device, and would trigger the mine if the tripwire was pulled away from the mine.
Usage
The S-mine was normally triggered by a three-pronged pressure sensor. It could also be modified to be triggered by a tripwire. A special tripwire adapter was provided by the German army. The steel tube that held the fuse was threaded to accept any standard German igniter or trigger, allowing the sensor to be removed and the mine to be deliberately triggered by a human operator. When triggered, the mine detonated in two stages (see diagram).
- (1) First, the mine was propelled 0.9–1.5 m (3–5 feet) into the air by a small propelling charge.
- (2) Once the optimum height was reached for wounding infantry and personnel, the main charge exploded.
- (3) The main charge of the mine was surrounded by roughly 360 ball bearings, short steel rods, or scrap metal pieces. These became metal shrapnel that sprayed horizontally from the mine at lethal speeds.
The time between triggering and detonation of the propelling charge varied between 3.9 and 4.5 seconds, depending on the age and condition of the mine. According to German documentation, the S-mine was lethal within 20 meters (22 yards) and could inflict casualties within 100 m (110 yards). American training manuals warned of casualties at up to about 140 m (150 yards). A common misconception about the S-mine is that it would not detonate until its victim stepped off the trigger. This fallacy was propagated by incorrect United States propaganda during World War II. The mine would detonate whether the trigger was depressed or not. Standing still or attempting to run from the S-mine would be equally dangerous. The most effective way to survive the mine's detonation would not be to flee but to fall prone as quickly as possible.
Detection and disarming
The S-mine was constructed mostly of metal, so it could be easily detected by metal detectors. However, such expensive and bulky equipment was rarely available to infantry units and was prone to malfunction. The mine could also be detected through careful manual probing, a time-consuming process. Using a knife or a bayonet, an infantryman would probe at a low angle through the soil. It was important to probe at an angle that would not accidentally depress the pressure sensor.
Once discovered, disarming the S-mine was fairly simple. To prevent triggering while the mine was being planted, the German pressure sensor featured a hole where a safety pin kept the sensor from being depressed. This pin was removed once the mine was planted. If the discovered mine was fitted with the pressure sensor, the disarming personnel would slip a pin (such as a sewing pin) into this hole. If the device was armed with a tripwire or electrical trigger, this could simply be cut. Germans were known to use booby traps to discourage this, so caution was suggested. The mine could then be removed carefully from the ground and the sensor easily unscrewed. If it was necessary to render the mine completely inert, three plugs on the top top granted access to the three detonators inside the mine. These could be unscrewed and the detonators removed.
Internal workings
These diagrams depict the SMi-35 landmine's internal workings, along with the workings of the standard three-prong pressure sensor. The safety pin for the sensor and the three removable plugs for the detonators are clearly visible.
Imitations
The S-mine was an extremely successful design and has been widely copied. Various armies and groups have used similarly designed bounding mines throughout the world.
The Finnish army began purchasing the SMi-35 model S-mine from Nazi Germany following the Winter War. This was part of a larger military assistance agreement between the two nations. Finnish forces achieved great success with the S-mine, but the monetary cost of the mine was considerable. During the Continuation War, the Finns attempted to produce their own version of the mine but with no success.
The American M-1939 bounding mine was inspired by the success of the S-mine. The American army was impressed by the S-mine's role in thwarting the French offensive in the German Saar region at the beginning of World War II. After the war, the American army developed their M16 series of mines directly from captured S-mine designs. The Soviet Union also based the design of its OZM series of landmines on the German S-mine. The Soviet mines tended to be far simpler internally; instead of being filled with ball bearings or scrap metal, the OZM-4 mine was given a solid cast-iron body that would fragment on its own. Later, the OZM-72 bounding mine was filled with steel rods, returning to the original concept of the S-mine. Both of these mines are still being produced by Russia.
Other nations that have produced S-mine-inspired designs include the People's Republic of China and Italy. The use of landmines remains a controversial issue to this day. Antipersonnel mines like the S-mine have been the subject of repeated treaties and human rights objections, and are the subject of extensive international debate.
References
- Lieutenant-Colonel C.E.E. Sloan, Mine Warfare on Land, Brassey’s, London, 1986.
- US Army Field Manual FM 5-31, 1943.
External links
- Lone Sentry: TM-E 30-451 Handbook - US Army Handbook entry for SMi-35 and SMi-44 mines, as well as other German mines
- Technical Intelligence Bulletins Sept - Details relationship between S-mine and later American designs
- Infoseek Japan - Japanese website featuring US military images and diagrams of the S-mine
- Weapons of the Italian Campaign - Details the use of the S-mine and other weapons during the Allied liberation of Italy