The Battering Ram is the earliest, simplest, and, until the development of heavy artillery in the 1300's, most effective device for destroying stone walls and the ordinary defenses of fortified towns. The primitive ram was a huge beam of seasoned and tough wood, hoisted on the shoulders of men. Running with it at full speed against a wall, gate, or palisade, they did what damage they could with one charge after another. Ancient armies used two different kinds of battering ram- one type was suspended and swinging, like a pendulum, and the other moved on rollers.
The swinging ram resembled a ship's mast and was suspended horizontally at its center of gravity by means of chains or cords, from a movable frame. Waxed cord was bound around the beam at short intervals, and cords at the back end were pulled in unison to cause the pendulum motion.
The rolling ram was much the same in its general construction, except that instead of a pendulum motion, it was given only a simple to-and-fro motion, produced by men pulling on cords passing over pulleys. The rolling ram seems to have been first used at the siege of Byzantium in 196 a.d. These rams often were extremely heavy. In Roman literature, Appian writes that at the siege of Carthage he saw two rams so colossal that 100 men worked each; Vitruvius affirms that the beam was often from 100 to 120 feet (30-36 meters) in length; and Justus Lipsius describes some as 180 feet long and 2 feet 4 inches in diameter (54.9 by 0.7 meters), with an iron head weighing at least a ton and a half, and a total weight of more than 45,000 pounds (20,385 kg).
The efficacy of the ram depended almost entirely upon the proper timing of its intervals of oscillation. At first it would produce no obvious effect upon the wall; but repeated blows soon caused a barely perceptible tremor in the wall, then more extensive vibrations. The attackers adjusted the oscillations of the ram to that of the wall, until finally the wall gave way.