Slavery was fundamental to the early Romans because Rome was an agrarian society, and there was always a need for farm labor. Not all Roman slaves were the defeated enemy: some were purchased at auction, others were freemen enslaved through their own misdeeds. Until 325 B.C, Roman citizens could be placed in servitude if they were unable to pay their debts.
It is estimated that Rome had 17,000 slaves in 475 B.C. and 40,000 by 325 B.C. Those numbers pale beside the 55,000 captured Carthaginians brought back from Africa at the end of the Third Punic War in 146 B.C. By then, slavery had become a significant problem for the Republic, as slaves took the jobs of freemen in the city, displaced them as farm labor, and began to serve in the army.