During the Second Punic War, King Philip V of Macedonia made an alliance with Hannibal against Rome. The Romans, in turn, allied themselves with the Aetolian League of Greek city-states. The cities of the league bore the brunt of the fighting on the Greek peninsula until after the Romans had defeated Hannibal in 202 B.C.E. Then the Roman legions were deployed against the Macedonians, who were defeated in a series of wars. Roman armies also won significant victories against the forces of the Seleucid emperors, and that empire shrank. In 148 B.C.E., they made Macedonia into a Roman province. Another decisive victory came in 146 B.C.E., when the Romans attacked the city of Corinth. Just as they had at Carthage earlier that year, the Romans destroyed the city, looting it for treasure. In 133 B.C.E., the king of Pergamum bequeathed his kingdom to the Romans. The Ptolemies of Egypt retained formal control of their kingdom, but they obeyed Roman wishes in terms of trade policy.

Once the Romans had conquered the Hellenistic world, they faced the formidable challenge of governing it without further warfare. They began to create political and administrative machinery to hold the Mediterranean together under a political system of provinces ruled by governors sent from Rome.