Pilium

The pilum (plural pila; Classical Latin: [ˈpiːlũː]) was a javelin commonly used by the Roman army in ancient times. It was generally about 2 metres (6 ft 7 in) long overall, consisting of an iron shank about 7 millimetres (0.28 in) in diameter and 60 centimetres (24 in) long with a pyramidal head. The shank was joined to the wooden shaft by either a socket or a flat tang.

The total weight of a pilum was between 2 and 5 kilograms (4.4 and 11.0 lb), with the versions produced during the earlier Republic era being slightly heavier than those produced in the later Empire era.

The iron shank was the key to the function of the pilum. The weapon had a hard pyramidal tip but the shank was made of softer iron. This softness would cause the shank to bend after impact, thus rendering the weapon useless to the enemy who might throw it back. However, there were many cases where the whole shank was hardened, making the pilum more suitable as a close quarters melee weapon, while also making it useful for enemy soldiers to pick up and throw back. Also, if the pilum struck a shield it might embed itself and thus the bending of the shank would force the enemy to discard their shield as it would render the shield impractical to use without removing the pilum from the shield, which in itself would be time consuming. Even if the shank did not bend, the pyramidal tip still made it difficult to pull out.

Although the bending of the pilum's shank is commonly seen to be an integral part of the weapon's design and as an intentional feature, there is little evidence to suggest this. The most commonly found artifacts suggest that the pilum was constructed to use the weight of the weapon to cause damage, most likely to be able to impale through armour and reach the enemy soldier's body. The combination of the weapon's weight and the aforementioned pyramidal tip (the design of which would be seen in the Medieval Era in the form of bodkin arrow tips), allowed the pilum to be a formidable armour-piercing weapon. Because the weapon was meant to be used against armour and use its own weight, as opposed to velocity, to cause damage, the bending of the shank seems to be a beneficial result of its intended use, which is to pierce through layers of armour. That the pilum needed to pierce layers of armour (through the shield, into body-armour, and past clothing) necessitated a lengthy shank, which was simply prone to bending. The momentum of the pilum caused the shank to bend upon impact, and, although unintended, this proved to be a useful characteristic of the weapon.

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