How was Rome’s treatment of the carthaginians different from its treatment of conquered peoples in earlier wars

Carthage represent the Roman Republic’s first truly expansionist war. For the first time, they were expanding beyond just the Italian peninsula and the surrounding islands. There was a legendary history with Carthage, though, and from the time of Aeneas, the Carthaginians and the Romans despised one another. As a result, once Carthage was defeated, the Phoenician ships in its harbor were burnt, the city was sacked, it’s people enslaved and the buildings and walls reduced to rubble. There was even a legend that the ground was sown with salt so that nothing would grow there for decades.

Rome was never again so harsh to an enemy state. Normally, existing populations weren’t enslaved en masse, only those that fought back. Additionally, Rome was traditionally very tolerant of existing traditions and local needs, assimilating them into the Republic/Empire. All people under Roman rule were considered Roman citizens, provided they weren’t slaves.