Animals have traditionally been used in warfare, especially horses, camels, elephants, mules, donkeys and dogs. Pigeons have been used to carry messages (with some 20,000 having been killed in the First and Second World Wars) and have been proposed as guidance devices for missiles. Bats have been tested as delivery systems for incendiary devices. Dogs, cats and pigs have been tested for the delivery of explosives and for torpedo guidance. In the light of research in public aquaria, marine mammals are increasingly exploited by the military whether for torpedo recovery, espionage or suicide missions.
Animals are extensively used in military research: animals are shot to determine the damage capacity of bullets and explosive devices; after being subjected to lethal doses of radiation, cats, dogs and other animals are run to death in rotary drums to determine their survival capacity; other animals are tested with biological and chemical weapons and then exposed to similar endurance tests.