Roman soldiers scaling the walls of a fortress using ladders mounted on boats. Image taken from "Poliorceticon sive de machinis tormentis telis" by Justus Lipsius (Joost Lips), 1602 edition. The Romans designed weaponry that both gave some protection to their men but also were designed to smash into fortifications. Siege towers were used to get troops over an enemy curtain wall. When a siege tower was near a wall, it would drop a gangplank between it and the wall. Troops could then rush onto the walls and into the castle or city. Battering rams had a cover to them made of wood and animal hide. This combination was enough to stop arrows, but was still flammable. The Romans also developed an early form of large attack catapults called onagers. These hurled large stone boulders at a wall to smash it down. The Romans also used catapults to fire iron bolts at the lines of the enemy facing them. This image has been colorized.