La translatio imperii in Polibio

When inserting Sparta in the ‘translatio imperii’ outline, Polybius is not mixing, as often maintained, this outline with a list of cities, whose hegemony was exercised in Greece; on the contrary Sparta fits well in the succession of empires, because its rule extended both on earth and sea, even if it lasted twelve years only: so it had been the only complete empire before that of the Romans.