The Battle of Verdun was fought from February 21 - December 18, 1916 during WWI on the Western Front between the German and French armies, on hills north of Verdun-sur-Meuse in north-eastern France. The concentration of so much fighting in such a small area devastated the land, resulting in miserable conditions for troops on both sides. Rain combined with the constant tearing up of the ground turned the clay of the area to a wasteland of mud full of human remains. Shell craters became filled with a liquid ooze, becoming so slippery that troops who fell into them or took cover in them could drown. Forests were reduced to tangled piles of wood by constant artillery-fire and eventually obliterated. The effect on soldiers in the battle was devastating, many broke down with shell-shock and some French troops attempted to desert to Spain, those who were caught being shot. It was the longest and one of the most costly battles in human history; other recent estimates increase the number of casualties to 976,000.