The Ballista was an ancient missile launcher designed to hurl javelins or heavy balls. Ballistae were powered by torsion derived from two thick skeins of twisted cords through which were thrust two separate arms joined at their ends by the cord that propelled the missile. The cords were traditionally made of human hair when the Greeks/Romans ran out of rope. The much smaller carroballistae were of similar design but were sufficiently mobile that Roman legions took them into the field on carts. The largest ballistae were quite accurate in hurling 30 kg projectiles up to over 450 meters.
The ballista was used in the first invasion of Britain. The two sides were: Rome against Britain. The first of Caesar’s invasions of Britain took place in 55BC, after a rapid and successful initial conquest of Gaul, in part as an expedition, and more practically to try to put an end to the reinforcements sent by the native Britons (native people of Britain) to fight the Romans in Gaul. During the invasions, Caesar ordered the warships. They were likely to impress the native British people due to its strange shape. Within the warships were many slings, bows, artillery and other machines the Britons were unfamiliar with. These machineries included the Roman Ballista.
In this invasion, the Britons were scared by the strange shapes of the machines. After Caesar fired the ballistae and other siege weapons, the native British people were forced to drive back and retreat because they had nothing to defend the projectiles travelling at nearly 40 kilometres per hour. From this, we can see that the ballista brought about a sense of fear in the air when taken into battle. The Britons instantly retreated after knowing what these weapons could do to them.