The German S-mine (Schrapnellmine), also known as Bouncing Betty, is the best-known version of a class of mines known as bounding mines. These mines launch into the air at about waist height and explode, propelling shrapnel horizontally at lethal speeds. The S-mine was an anti-personnel 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 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 (TM-E 30-451, 1945).

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 (Valias, 2005). 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.

CHARACTER
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 fuze, where its trigger or sensor was attached. The SMi-35 had a central fuze, while the SMi-44 had an offset fuze. 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 (TM-E 30-451, 1945).

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 fuze inside the device. The standard pressure sensor used a percussion cap for this purpose (FM 5-31, 1943).

The main fuze 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 ensure 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 (TM-E 30-451, 1945).

DETECTION & DEACTIVATION
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 (FM 5-31, 1943).
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 granted access to the three detonators inside the mine. These could be unscrewed and the detonators removed (FM 5-31, 1943).