creates hollows on the downwind side of obstacles, such as trees, buildings, and bushes, which provide observation points or firing positions. Snowdrifts may provide cover for soldiers to approach an objective. Soviet Army doctrine cited as the threshold snow depth that impairs mobility for troops, cavalry and vehicles, except tanks for which the threshold was . Thaw Thawing conditions can impair mobility and put soldiers at risk of trench foot by turning soil to mud; it can also weaken and break up ice cover on bodies of water. Maintaining roads becomes more difficult during spring-thaw run-off periods and requires mud removal by heavy equipment. Slushy and muddy ground causes clothing and equipment to become wet, damp and dirty. Muddy conditions greatly inhibited Napoleon's ability to maneuver in Russia in the autumn of 1812 and also the German attempt to take Moscow in the autumn of 1941. The 1942 Taschenbuch für den Winterkrieg acknowledges that neither tracked nor wheeled vehicles can maneuver during conditions of thaw and that aircraft operations must be constrained to concrete runways. It addresses minimizing the use of roads during this period and dismantling bridges that are likely to be taken out by ice floes. It emphasizes how positions in frozen soil must be improved to avoid deterioration from thaw and the necessity of changing uniforms from ones for cold to those for wet conditions. Tactics The dominant tactical concern in cold conditions is the ability to maneuver in vehicles or on foot. Additionally, during winter, night operations become the norm at higher latitudes with their long periods of darkness. Snow enhances night vision because of high reflectivity and the visibility of combatants against the white background. Mounted movement The German Taschenbuch für den Winterkrieg emphasizes reconnaissance to ascertain the conditions and capacity of the roads to be used. It describes snow clearing from roads and recovery of bogged-down vehicles. Soviet Army doctrine emphasized the use of sleds for transporting machine guns and mortars over snow, towed in a train by tracked tractors. It addressed the need to pre-heat tanks for use in winter and their application in advance of marching troops to take out enemy positions. Finnish military doctrine calls for small-unit movements with Anti-tank guided missiles and multiple launch rocket systems to attack foreign forces that have entered the country. US Army guidance advocates that over snow-covered terrain, vehicles may be employed to establish and