Roman Siege Machines
To be successful at conquering their enemies, Romans had to develop good methods of breaking into walled forts and cities. Three weapons the Romans developed to help with the task were the onager, ballista, and catapulta. The onager was type of catapult used for hurling large rocks up to one thousand feet (three hundred meters).
The ballista and catapulta were types of high-powered crossbows which hurled missiles long distances or pierce armor. The Romans are known to have built movable towers to capture walled cities. They also built dirt ramps to the top of walls. The tortoise formation used by the infantry was designed for such sieges.