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.