The peltasts raised from the Agrianes, a Paeonian tribe, were the elite light infantry of the Macedonian army.
They were often used to cover the right flank of the army in battle, being posted to the right of the Companion cavalry, a position of considerable honour.
They were almost invariably part of any force on detached duty, especially missions requiring speed of movement.
Other nationalities also provided peltasts for the Macedonian army.
Especially numerous were the Thracians; the Thracian peltasts performed the same function in battle as the Agrianians, but for the left wing of the army.
It is unclear if the Thracians, Paeonians, and Illyrians fighting as javelin throwers, slingers, and archers serving in Macedonian armies from the reign of Philip II onward were conscripted as allies via a treaty or were simply hired mercenaries.

Peltasts were armed with a number of javelins and a sword, carried a light shield but wore no armour, though they sometimes had helmets; they were adept at skirmishing and were often used to guard the flanks of more heavily equipped infantry.
They usually adopted an open order when facing enemy heavy infantry.
They could throw their javelins at will at the enemy and, unencumbered by armour or heavy shields, easily evade any counter-charges made by heavily equipped hoplites.
They were, however, quite vulnerable to shock-capable cavalry and often operated to particular advantage on broken ground where cavalry was useless and heavy infantry found it difficult to maintain formation.
The peltasts raised from the Agrianes, a Paeonian tribe, were the elite light infantry of the Macedonian army. They were often used to cover the right flank of the army in battle, being posted to the right of the Companion cavalry, a position of considerable honour. They were almost invariably part of any force on detached duty, especially missions requiring speed of movement. Other nationalities also provided peltasts for the Macedonian army. Especially numerous were the Thracians; the Thracian peltasts performed the same function in battle as the Agrianians, but for the left wing of the army. It is unclear if the Thracians, Paeonians, and Illyrians fighting as javelin throwers, slingers, and archers serving in Macedonian armies from the reign of Philip II onward were conscripted as allies via a treaty or were simply hired mercenaries.
Peltasts were armed with a number of javelins and a sword, carried a light shield but wore no armour, though they sometimes had helmets; they were adept at skirmishing and were often used to guard the flanks of more heavily equipped infantry. They usually adopted an open order when facing enemy heavy infantry. They could throw their javelins at will at the enemy and, unencumbered by armour or heavy shields, easily evade any counter-charges made by heavily equipped hoplites. They were, however, quite vulnerable to shock-capable cavalry and often operated to particular advantage on broken ground where cavalry was useless and heavy infantry found it difficult to maintain formation.
Ancient Macedonian army