. Historical references show artillery was first employed by the Roman legions at Syracuse in 399 BC,[citation needed] well before the Christian era. Until the introduction of gunpowder into western warfare, artillery was dependent upon mechanical energy which not only severely limited the kinetic energy of the projectiles, it also required the construction of very large engines to store sufficient energy. A 1st-century BC Roman catapult launching 6.55 kg (14.4 lb) stones achieved a kinetic energy of 16,000 joules, compared to a mid-19th-century 12-pounder gun, which fired a 4.1 kg (9.0 lb) round, with a kinetic energy of 240,000 joules, or a late 20th century US battleship that fired a 1,225 kg (2,701 lb) projectile from its main battery with an energy level surpassing 350,000,000 joules.
The future emperor Vespasian used proficiency with Roman artillery to rapidly reduce the Celtic hillforts in Britain during his participation in a campaign there. It helped bring him to prominence, and when he declared for the emperor job, rivals either gave in and backed him, after they peed their togas, or killed themselves. Vespasian also managed to survive the years of Nero, including an embarrassing (and potentially deadly) incident when he nodded off during one of Nero’s no-talent recitals.