Accurate reconstruction of an onager, produced in the 1930s under the direction of the Istituto Storico e di Cultura dell'Arma del Genio. The onager was a war machine used to hurl blunt projectiles, such as stones. Its name derives from the animal of the same name, a type of Southeastern Asian donkey, whose kicking was compared with the action of the weapon. It was formed from a massive wooden frame whose central part was furnished with a propulsion mechanism formed from two bands of elastic material. Enclosed within this web was an arm, made of a thick pole, furnished with a sling with a projectile. This arm was lowered under tension by a winch. By making the release mechanism function, the pole was thrown forward with great force and hit an inclined surface in such a way that the projectile was launched on an arched path. The onager was capable of hurling blunt projectiles to a height of 40 m and a distance of 30 m. By changing the attachment of the sling, the path and the height of the projectile could be altered.