“One type of expense incurred in modern wars was not always present in the ancient world: paying the troops.
As we have seen, in the classical city state citizenship was bound up with military service.
For a long time city states thus had no need to pay their citizen-soldiers.
In the Greek world the only city for which we have much evidence of military pay is Athens. There, pay appears to have been introduced in the 5th century BC as Athens acquired an empire, and at first it seems to have been a form of living allowance.
During the Peloponnesian War the concept of military pay broadened to include remuneration for service, and other Greek cities began to pay their soldiers.
The Romans introduced military pay during the siege of Veii, which ended in 396 BC.
The emperor Augustus set up a special treasury and introduced two new taxes to pay the professional army of the principate. It is to be doubted if basic military pay was ever a road to riches. In the principate if a soldier lived long enough to collect his retirement bonus, he would be comfortably set up for the rest of his life.
Otherwise, throughout the classical world, a soldier would have to look to booty for serious economic advancement.” (Sidebottom, 2004, p.74).
Sidebottom, H. (2004) Ancient Warfare: A Very Short Introduction. Oxford: Oxford University Press.