World War I cost France 1,357,800 dead, 4,266,000 wounded (of whom 1.5 million were permanently maimed) and 537,000 made prisoner or missing - exactly 73% of the 8,410,000 men mobilized.
France had 40 million citizens at the start of the war; six in ten men between the ages of eighteen and twenty-eight died or were permanently maimed.
The use of horses in World War I marked a transitional period in the evolution of armed conflict. Cavalry units were initially considered essential offensive elements of a military force, but over the course of the war, the vulnerability of horses to modern machine gun and artillery fire reduced their utility on the battlefield. This paralleled the development of tanks, which would ultimately replace cavalry in shock tactics. While the perceived value of the horse in war changed dramatically, horses still played a significant role throughout the war.
The military mainly used horses for logistical support during the war; they were better than mechanized vehicles at traveling through deep mud and over rough terrain. Horses were used for reconnaissance and for carrying messengers, as well as pulling artillery, ambulances, and supply wagons. The presence of horses often increased morale among the soldiers at the front, but the animals contributed to disease and poor sanitation in camps, caused by their manure and carcasses. The value of horses, and the increasing difficulty of replacing them, was such that by 1917 some troops were told that the loss of a horse was of greater tactical concern than the loss of a human soldier. Ultimately, the Allied blockade prevented the Central Powers from importing horses to replace those lost, which contributed to Germany's defeat. By the end of the war, even the well-supplied U.S. Army was short of horses.