<P> They had likewise two other javelins, the largest of which was composed of a staff five feet and a half long and a triangular head of iron nine inches (230 mm) long . This was formerly called the pilum, but now it is known by the name of spiculum . The soldiers were particularly exercised in the use of this weapon, because when thrown with force and skill it often penetrated the shields of the foot and the cuirasses of the horse . </P> <P> It may be argued that a short iron shaft has very few confirmations from archaeology . Vegetius wrote about a one - foot iron shaft because at Vegetius' time the pilum had disappeared and been replaced by similar shorter weapons such as the plumbatae and the spiculum . </P> <P> Thanks in part to experimental archaeology, it is generally believed that the pilum's design evolved to be armour - piercing: the pyramidal head would punch a small hole through an enemy shield allowing the thin shank to pass through and penetrate a distance sufficient to wound the man behind it . The thick wooden shaft provided the weight behind the punch . </P> <P> In one description, one of the two iron nails that held the iron shaft in place was replaced with a weak wooden pin that would break on impact causing the shaft to twist sideways . Gaius Marius is sometimes given credit for this modification . </P>

How far could a roman throw a javelin