The Byzantine navy or the Eastern Roman navy was the naval force of the East Roman or Byzantine Empire. Like the empire it served, it was a direct continuation from its imperial Roman predecessor, but played a far greater role in the defense and survival of the state than its earlier iteration. While the fleets of the unified Roman Empire faced few great naval threats, operating as a policing force vastly inferior in power and prestige to the legions, the sea became vital to the very existence of the empire in the east, which several historians have called a "maritime empire".