The earliest Roman naval battles against Carthage also emphasized boarding. Since the Romans were primarily a land-based army, they could not effectively combat the Carthaginian navy, and subsequently lost several sea battles. The corvus, a boarding ramp with two steel spikes, was the Roman answer to this problem. Roman sailors piloted their ship alongside a Carthaginian ship, dropped the corvus from one deck to the other, and sent their soldiers across the board, assaulting the ship. The Carthaginian navy, unprepared for this "land combat" on the oceans, lost several ships to this tactic. This invention secured Roman naval dominance in the Mediterranean Sea for several centuries.