Rome called the Mediterranean mare nostrum — our sea — with a proprietorial confidence that would have seemed absurd in the third century BC, when Rome barely had a navy and Carthage’s fleet controlled the western Mediterranean. That the claim became factually accurate within a century and remained so for four more is one of the more striking strategic transformations in ancient history: a land power with no maritime tradition built a navy, fought the greatest naval power of the ancient world, and eventually achieved a dominance over the Mediterranean so complete that it had eliminated piracy, secured trade routes, and reduced naval competition to the point where maintaining a large battle fleet was unnecessary. Rome conquered the sea the same way it conquered everything else — not through inherent advantage but through organizational capacity and willingness to pay whatever the victory cost.