In the late 4th and early 3rd centuries BC, men were sorted into classes based on wealth, the principes being the wealthiest after the triarii. Principes were armed with a pilum, which is a throwing spear, and a sword, which was used after the spear had been thrown. They fought in a quincunx formation, usually carrying scuta, large rectangular shields, and bronze helmets, often with a number of feathers fixed onto the top to increase stature. They wore heavier armour types, the most common form being chainmail, which offered a good degree of protection without hindering movement.

By the time of the Second Punic War of the late 3rd century BC, a new system gradually came into being. Infantry were sorted into classes according to age and experience rather than wealth, the principes being older veterans with a greater degree of experience. Their equipment and role was very similar to the previous system, except they now carried swords, or gladii, instead of spears.