The question of how Rome transitioned from a city-state to a territorial empire is one of the fundamental questions in Roman history. In Italy, the process was largely one of gradual incorporation through a system of differential alliances: some communities became Roman citizens, others retained their own institutions while bearing military obligations. This variable arrangement was what held when Hannibal tried to peel allies away.

Outside Italy, the process was more varied and more often explicitly imperial. The acquisition of Sicily, Sardinia, and Corsica after the First Punic War established the template: provinces under Roman governors, paying tribute, with local autonomy varying by circumstance.

William Harris's argument in War and Imperialism in Republican Rome — that Roman imperialism was structurally driven by the needs of the senatorial class for military glory and the economic benefits of conquest — remains controversial but essential. Rome's expansion was not defensive reflex but something with genuine positive drivers in Roman domestic politics.