Over 16 million animals served in the First World War. They were used for transport, communication and companionship.
In 1914, both sides had large cavalry forces. Horse and camel-mounted troops were used in the desert campaigns throughout the war, but on the Western Front, new weapons like the machine gun made cavalry charges increasingly difficult.
However, animals remained a crucial part of the war effort. Horses, donkeys, mules and camels carried food, water, ammunition and medical supplies to men at the front, and dogs and pigeons carried messages. Canaries were used to detect poisonous gas, and cats and dogs were trained to hunt rats in the trenches.
Animals were not only used for work. Dogs, cats, and more unusual animals including monkeys, bears and lions, were kept as pets and mascots to raise morale and provide comfort amidst the hardships of war.
This fox cub was the mascot of No.32 Squadron. The cub is pictured at Humieres Aerodrome, St Pol, France in May 1918. It looks as if the cub would like to take a flight in this bi-plane fighter.
Camels carry wounded men to safety on the North West Frontier of India in 1917. Camels were also used in the Sinai and Palestine campaigns. Their ability to carry heavy loads and go without water made them an ideal mode of transport in hot climates.
French Red Cross dogs line up for inspection on the Western Front, 1914. These specially trained dogs wore harnesses containing medical equipment, which they delivered to injured soldiers on the battlefield.
British troops scraping mud from a mule near Bernafay Wood on the Western Front, 1916. British military authorities tried to ensure that animal handlers cared for their animals properly.