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. Frostbite Frostbite is localized damage to skin and other tissues due to freezing. At or below , blood vessels close to the skin start to constrict, and blood is shunted away from the extremities. The same response may also be a result of exposure to high winds. This constriction helps to preserve core body temperature. In extreme cold, or when the body is exposed to cold for long periods, this protective strategy can reduce blood flow in some areas of the body to dangerously low levels. This lack of blood leads to the eventual freezing and death of skin tissue in the affected areas. Frostbite was responsible for over one million casualties in wars in the 20th century. Adequate insulation from clothing is the best way to avoid hypothermia in the field. Training by nation The following nations report regular training programs in cold-weather warfare: Canada – In 2008, the Canadian Forces established the Nanisivik Naval Facility, a winter warfare training center above the arctic circle in Resolute, Nunavut for annual exercises. China – The People's Liberation Army trains annually in regions subject to harsh winter conditions. Lightly armed border patrol units are mounted on horseback or snowmobiles and are expected to provide early detection of incursion. Finland – The Finnish Defence Forces train every conscript for skiing and Arctic warfare regardless of the branch, approximately 25,000 soldiers per year. Finland also trains US Army students in Arctic warfare. Germany – The Bundeswehr maintains its mountain troops in Bavaria. After the 2001 disbandment of the 1st Mountain Division, mountain troops were reorganized as the Gebirgsjägerbrigade 23 with a strength of 5,000 Troops. India – The Indian Army trains 100 officers and 400 non-commissioned officers and junior commissioned officers annually, at its High Altitude Warfare School. Its graduates are assigned to the Siachen Glacier border garrison. Iran – Members of the 65th Airborne Special Forces Brigade train for warfare on snow at their winter camp in Emamzadeh Hashem, Iran. Italy - The Alpini are the Italian Army's specialist mountain infantry. Established in 1872, they are the oldest active mountain infantry in the world. Japan – In the Japan Ground Self-Defense