Scorpio (weapon)

[3] The fourth century army officer and historian Ammianus Marcellinus witnessed the use of scorpiones during several engagements in the Persian wars of Constantius II, and described the one-armed version as synonymous with the onager, with the vertical upraised arm as the 'scorpion's sting'.

[2] The complexity of construction and in particular the torsion springs (which the Romans referred to as tormenta) led to great sensitivity to any variation in temperature or moisture, which limited their use.

[4] In 52 BC, during the siege of Avaricum in the war against the Gauls, Julius Caesar mentions the scorpio in use as an anti-personnel weapon against the Gallic town's defenders.

According to Vegetius, the Roman Empire ideally fielded fifty-five carroballistae per legion, one for every century, of whom ten men would be deputed to operate the machine.

Scorpions could be used in an artillery battery at the top of a hill or other high ground, the side of which was protected by the main body of the legion.