Cold-weather warfare
Trench foot is a medical condition caused by prolonged exposure of the feet to damp, unsanitary, and cold conditions at temperatures as warm as for as few as 13 hours. Exposure to these environmental conditions causes deterioration and destruction of the capillaries and leads to morbidity of the surrounding flesh. Affected feet may become numb, affected by erythema (turning red) or cyanosis (turning blue) as a result of poor blood supply, and may begin emanating a decaying odour if the early stages of necrosis (tissue death) set in. As the condition worsens, feet may also begin to swell. Advanced trench foot often involves blisters and open sores, which lead to fungal infections. If left untreated, trench foot usually results in gangrene, which may require amputation. If trench foot is treated properly, complete recovery is normal, though it is marked by severe short-term pain when feeling returns. Trench foot affected tens of thousands of soldiers engaged in trench warfare in World War I. Keeping feet warm and dry, or at least changing into warm and dry replacement footgear, is the best way to avoid trench foot.
Boot (torture)
A similar implement, the "foot press", consisted of a pair of horizontal iron plates slowly tightened around the bare foot by means of a crank mechanism, squeezing the foot with sufficient force to pulverize the bones. Although it was quite standard to line the lower plate with ribs to prevent the foot from popping out of the grip of the instrument as it became sweatier, a crueler variant of this device—typically encountered in Nuremberg, Germany—lined the upper plate with hundreds of sharp spikes. A version from Venice, sometimes called the "foot screw" or "toe breaker", connected the crank mechanism to a drill that slowly mutilated the foot by boring a hole through the center of the instep as the press was tightened. In the most extreme case, the press was tightened until the plates met, so grinding the foot bones to powder.