Final answer:
Carthage was the preeminent power and a threat to Rome in the western Mediterranean by 300 BC, leading to the Punic Wars. This rivalry between Rome and Carthage led to the famous series of conflicts known as the Punic Wars, beginning in 264 BCE and concluding with Rome's victory in 146 BCE, solidifying Rome's dominance in the Mediterranean.
Step-by-step explanation:
By 300 BC, the power preeminent and a threat to Rome in the western Mediterranean was Carthage. Carthage, a North-African trading empire with Phoenician roots, had become increasingly powerful and established control over trade routes and territories which ultimately led to conflict with the expanding Roman Republic. This rivalry between Rome and Carthage led to the famous series of conflicts known as the Punic Wars, beginning in 264 BCE and concluding with Rome's victory in 146 BCE, solidifying Rome's dominance in the Mediterranean.