Throughout the history of Carthage it is often talked about how their armies were primarily mercenaries. But in conflicts with Syracuse and especially Rome, they both seemed to have been capable of continually drawing troops from citizen bases and allied cities.
Was their citizen base just very small comparably? Or was there something in their early history that made them prefer to pay people to fight instead of fight themselves?
More input is always welcome; for the meantime, this answer by u/Jollydevil6 on the Carthaginian army may be of interest to you.