τῆς ἀρχῆς ἅμα προκοπτόντων ἐκείνοις

From LSJ

μέγα γὰρ τὸ τῆς θαλάσσης κράτοςgreat is the power of the country that controls the sea, control of the sea is a great thing, the dominion of the sea is a great matter, the rule of the sea is a great matter, the rule of the sea is indeed a great matter, control of the sea is a paramount advantage

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