During some periods of the war, 1,000 horses per day were arriving in Europe as remounts for British troops, to replace horses lost. Equine casualties were especially high during battles of attrition, such as the 1916 Battle of Verdun between French and German forces. In one day in March, 7,000 horses were killed by long-range shelling on both sides, including 97 killed by a single shot from a French naval gun.[66] By 1917, Britain had over a million horses and mules in service, but harsh conditions, especially during winter, resulted in heavy losses, particularly amongst the Clydesdale horses, the main breed used to haul the guns. Over the course of the war, Britain lost over 484,000 horses, one horse for every two men.[67] A small number of these, 210, were killed by poison gas.[34]