Military animals are trained animals that are used in warfare and other combat related activities. As working animals, different military animals serve different functions. Horses, elephants, camels, and other animals have been used for both transportation and mounted attack. Pigeons were used for communication and photographic espionage. Many other animals have been reportedly used in various specialized military functions, including rats and pigs. Dogs have long been employed in a wide variety of military purposes, more recently focusing on guarding and bomb detection, and along with dolphins and sea lions are in active use today.
Source: Wikipedia
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.