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.