Catapults have been used in siege warfare throughout history. They reached Europe at the beginning of the Middle Ages and were used widely by the French, who introduced them into England in 1216 during the Siege of Dover. Catapults became obsolete with the introduction of gunpowder in the 14th century.
The catapult was used to propel projectiles at and over the wall of a castle, or a city. It was a key weapon in medieval warfare, breaking the siege more quickly than cutting off supplies.
It was the first instrument of biological warfare. Rotting animals and corpses infected with the Black Death would be propelled over the wall to spread disease among the inhabitants.
Flaming objects would be used to kill large numbers of the besieged force with a single throw, especially those on the battlements, while rocks would be used to break down the castle itself, or the city wall, and expose the people hiding inside.
The Ballista was basically a giant crossbow that shot large numbers of arrows and darts along a flat trajectory, similar to flicking mashed potato across the dinner table. The Ballista was also known as the Springald.
Mangonels were giant catapults with wheels capable of firing rocks and other large projectiles great distances, usually aimed at castle walls. Items were placed in a bowl or bucket and unleashed using an arm. Also known as the Onager.
The mighty Trebauchet was used to propel large numbers of stones, or flaming objects in one go. It was considered the deadliest catapult of all.
Medieval Europe was covered in dense forest, so wood was readily available. The lack of roads meant large catapults were impossible to transport. The commander would decide what type of catapult was required, while the engineers would be responsible for building it with the besieged inhabitants looking on.