The peltasts, usually serving as skirmishers, were armed with several javelins, often with throwing straps to increase stand-off power.
The peltasts hurled their javelins at the enemy's heavier troops, the hoplite phalanx, in order to break their lines so that their own army's hoplites could destroy the weakened enemy formation.
A pilum usually weighed between two and four kilograms, with the versions produced during the Empire being somewhat lighter.
Pictorial evidence suggests that some versions of the weapon were weighted with a lead ball at the base of the shank in order to increase penetrative power, but no archaeological specimens have been found.
However, hurling devices do exist to assist the javelin thrower in achieving greater distance. The word javelin comes from Middle English and it derives from Old French javelin, a diminutive of javelot, which meant spear.
The word javelot probably originated from one of the Celtic languages.
This marked the first recorded occasion in ancient Greek military history in which a force entirely made up of peltasts had defeated a force of hoplites.
In the battle of Lechaeum, the Athenian general Iphicrates took advantage of the fact that a Spartan hoplite phalanx operating near Corinth was moving in the open field without the protection of any missile-throwing troops.
He decided to ambush it with his force of peltasts.
Recent experiments have shown pila to have a range of about 30 metres, although the effective range is only about 15 to 20 metres.
Pila were sometimes referred to as javelins, but the archaic term for the javelin was verutum.