Literally pilum means “javelin”, in the plural pila. It was a legionary javelin used to throw at a distance before the fight. The weapon, most likely of Etruscan or Samnites origin, was refined and introduced into the regular Roman army.
At the beginning of the Republic the legionaries of the first (hastati) and the second (principes) line of manipulators in the legion were usually equipped with two piles: larger, referred to as “pilum from afar” (pilum eminus) and smaller, called “close-up pilum” (pilum comminus). After the reform of Marius all legionaries were in possession of pilum, still having two.
Pilum bigger (heavy) was about 2,1 m long, of which 70 cm was found on the nipple, and the rest on the pole; and weight circa 2 kg. A small blade mounted on a long neck had the shape of a cone or pyramid, and sometimes a hook (pilum hamatum). The long neck of the slab made it possible to punch the blade into the opponent’s body after punching the shield.
The tip was fastened by means of an iron rivet passing through the oblong hole of the mainsail shaft and a wooden stick passing through the round precisely aligned second hole of the flat shaft of the mainsail which broke during the impact, causing displacement and additional impact of the wooden part in the main shaft. It increased his strength and made the pilum even useless after being missed to be used effectively by the enemy.
The uniqueness of pilum was in the way of joining metal and wooden parts. The loops were fastened with a sleeve or a hammered stick which broke during the impact, preventing the enemy from reusing the pilum. In addition, after hitting the target (eg. in a shield), the long spear neck was easily bent or broke, obstructing movements or forcing the enemy to discard the shield. A pyramid-shaped blade, sometimes with burrs, made it difficult to tear off the pilum after being hit. The effective range of the larger pilum projection was from 20 to 30m, thanks to additional ballast (lead) from lead or cast bronze, which significantly increased the range and depth of penetration.
Pilum smaller (light) was about 2m long and weight less than 1,5 kg. The design of the smaller javelin was identical to its larger counterpart, with the range being larger.
In addition to the light and heavy pilum, there was also a medium pilum, which weight was about 1/1,5 kg. All piles appeared in response to more and more powerful shields, to the piercing of which they were constructed.
Throwing the javelin followed a specific order. Due to the fact that not one man, but the whole line attacked at the same time, the effectiveness of the destruction increased.
The opponent’s shield was not a serious obstacle for a well-trained legionary. The javelin pierced her, as well as the man behind her. It also happened that in exceptional cases one spear pierced, due to the very long arrowhead, a warrior and his companion standing right behind him. Even if the pilum stopped in the shield without damaging the opponent, it burdened his shield, rendering it useless.
Romans often used to throw a javelin, a thong (ammentum), so that the javelin flew much further.