In 400 bc the ballista was made and it was made by the romans in 400 bc this weapon really helped the roman army when they were in war mainly because it uses a torsion bases weapon with a bolt meaning that it would be able to get better accuracy.  Another reasoning is that it would mean we could knock over the barrels easier by the force and impact of the bolt when people for the first time heard the ballista it was when king uzziah introduced it he made lot of weapons for the roman And he made in Jerusalem engines and was known by a lot of people and famous for a number of reasons the ballista was used by also the Greeks. The ballista was used for army they would put them on top of towers and put an arrow in it and the ballista wasn't that big it was pretty small because it was classified as a sniper and that was really good for the solders because you got better accuracy to aim at your opponent they didn't use arrows to fire at other solders they used bolts and so the ballista was very effective when it was in war but these weapons were deadly in 400 bc