Military of the Sasanian Empire

The Sasanian army was the primary military body of the Sasanian armed forces, serving alongside the Sasanian navy. The birth of the army dates back to the rise of Ardashir I (r. 224–241), the founder of the Sasanian Empire, to the throne. Ardashir aimed at the revival of the Persian Empire, and to further this aim, he reformed the military by forming a standing army which was under his personal command and whose officers were separate from satraps, local princes and nobility. He restored the Achaemenid military organizations, retained the Parthian cavalry model, and employed new types of armour and siege warfare techniques. This was the beginning for a military system which served him and his successors for over 400 years, during which the Sasanian Empire was, along with the Roman Empire and later the East Roman Empire, one of the two superpowers of Late Antiquity in Western Eurasia. The Sasanian army protected Eranshahr ("the realm of Iran") from the East against the incursions of central Asiatic nomads like the Hephthalites and Turks, while in the west it was engaged in a recurrent struggle against the Roman Empire. In the character of their warfare, the Persians of the Sasanian period differed greatly from their forebears under the Achaemenid kings. The principal changes which time had brought about were an almost entire disuse of the war chariot, the advance of the elephant corps into a very prominent and important position, and the increased use and pre-eminence of cavalry on the Parthian model, including both heavy cataphracts and horse-archers. Four main arms of the service were recognized, each standing on a different level: the elephants, the horse, the archers, and the ordinary footmen. In Pahlavi language, smaller divisions of the spāh were referred to as vasht and larger divisions were designated as gond. The Arabic word jund (جند), meaning "army", is derived from the latter. The Sassanid army was organized in accordance with the "decimal system", that is, its structural units were units that consistently counted tens, hundreds, thousands and tens of thousands of soldiers.