Carthage
Elimination of its rival power gave it control over the western Mediterranean.
The western Mediterranean.
Rome, which exterminated its rival in the Western Mediterranean, Carthage, and went on to dominate the Eastern Mediterranean.
Carthage .
Carthage .
It was a persistent rival for control of the Western Mediterranean.
The other state that was Rome's rival in the western Mediterranean was Carthage. Although perhaps it should be the other way around. As Rome emerged as the great rival of Carthage, because Carthage was founded before Rome.
Rome and Carthage clashed over control of Sicily, Rome developed naval power to rival Carthage's, and defeated it, gaining power in the Western Mediterranean.
Constantinople,Byzantium, New Rome or all as we know Istanbul.. but if its about military power of Roman Empire then Carthage
The punic wars
It was a rival to Rome for domination of the Western Mediterranean.
Rome eliminated its rival for control of the Western Mediterranean, and moved on to gain control of the Eastern Mediterranean.