care must be taken to ensure that the armour's reaction to fire does not cause issues with regards to the fire barrier being armoured to defeat explosions and projectiles in addition to fire, especially since both functions must be provided simultaneously, meaning they must be fire-tested together to provide realistic evidence of fitness for purpose. Combat drones use little to no vehicular armour as they are not manned vessels, this results in them being lightweight and small in size. Animal armour Horse armour Body armour for war horses has been used since at least 2000 BC. Cloth, leather, and metal protection covered cavalry horses in ancient civilisations, including ancient Egypt, Assyria, Persia, and Rome. Some formed heavy cavalry units of armoured horses and riders used to attack infantry and mounted archers. Armour for horses is called barding (also spelled bard or barb) especially when used by European knights. During the late Middle Ages as armour protection for knights became more effective, their mounts became targets. This vulnerability was exploited by the Scots at the Battle of Bannockburn in the 14th century, when horses were killed by the infantry, and for the English at the Battle of Crécy in the same century where longbowmen shot horses and the then dismounted French knights were killed by heavy infantry. Barding developed as a response to such events. Examples of armour for horses could be found as far back as classical antiquity. Cataphracts, with scale armour for both rider and horse, are believed by many historians to have influenced the later European knights, via contact with the Byzantine Empire. Surviving period examples of barding are rare; however, complete sets are on display at the Philadelphia Museum of Art, the Wallace Collection in London, the Royal Armouries in Leeds, and the Metropolitan Museum of Art in New York. Horse armour could be made in whole or in part of cuir bouilli (hardened leather), but surviving examples of this are especially rare. Elephant armour War elephants were first used in ancient times without armour, but armour was introduced because elephants injured by enemy weapons would often flee the battlefield. Elephant armour was often made from hardened leather, which was fitted onto an individual elephant while moist, then dried to create a hardened shell. Alternatively, metal armour pieces were sometimes sewn into heavy cloth. Later lamellar armour (small overlapping metal plates) was introduced. Full plate armour was