Germans retreating through Northern Italy, late in 1944, made increasingly desperate attempts to delay the Allied advance with mines and elaborately disguised booby traps. Trickiest of all were the “Pappmine” also known as the “Topfmine” and the “S” mine. The first used a case made of compressed wood-pulp, cardboard and tar along with glass plugs and components designed to be undetectable to Allied mine detectors. Often the only metallic part of the mines was the detonator. To enable the mines to be found by friendly forces, the mines were painted with a black sandy substance called Tarnsand. Allied forces found that although the mines were undetectable by Allied mine detectors, German mine detectors could find the mines when they had been marked with Tarnsand. The secret of Tarnsand was maintained until after the end of the war, when it was discovered that it was actually a mildly radioactive substance and the German mine detectors incorporated a simple Geiger counter. A British sapper neutralises a booby trap made from a Childs doll (1) A bottle of wine being disconnected from its deadly charge (2) A cunningly concealed egg-grenade (friction-fuse type) is removed from the branch of a pear tree (3) Neutralizing an antipersonnel mine Intended to be detonated by a trip-wire (4) The German S-mine (Schrapnellmine in German), also known as the 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 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. 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.