The Roman military was great and powerful, but didn’t just end up that way over night. They worked hard and, as the Romans are known for their excellent engineering skills, tried to stay one step ahead of the enemy. One way they did this was siege weapons, which was how the seized castles and lands. Siege engines ingeniously used both potential energy, kinetic energy and rotational kinetic energy to throw things very far, fast, and even accurately. Besiegers could fire 100-200 pound stones up to 1,000 feet. The main siege weapons were catapults. The catapult was used to destroy buildings and walls inside and outside of the castle, and it could also destroy an enemies morale by throwing severed heads of comrades.
The earliest model was the trebuchet. It started by using a large weight on one end of a pivoting arm. The arm was pulled back the missile was placed and then let go. The weight went down, the arm went, and the missile launched. The later model gained its power from a tightly wound skein of rope, hair, and skin. the skeins were twisted incredibly tight and then had a wooden arm up to sixty feet long placed in between them. The arm was pulled back using pulleys and rope, the missile was placed in the wood cup and then the arm was released. The arm sprang to a 90 degree angle where it was stopped by a large padded piece of wood. The arm was then brought back down and fired again.
Onagers were used by the Roman army, each centurion had them. When their rocks were hurled, whole sections of stone walls collapsed. They were great for sieges.
The ballista was like a much larger version of the crossbow used by besiegers. It got it’s power from being fired with sinew ropes and had two arms. Although the ballista was a great weapon it was hard to construct, therefore the Romans developed a new version called the Mangonel. It, like the Ballista also got it's power from sinew ropes but unlike the ballista which used two arms, the Mangonel only used one...