In short, the key to the salvation of the West was the Persian defeat by the Greeks, which required a victory at Salamis, which in turn could not have occurred without the repeated efforts—all against opposition—of a single Athenian statesman. Had he wavered, had he been killed, or had he lacked the moral and intellectual force to press home his arguments, it is likely that Greece would have become a satrapy of Persia.

Victor Davis Hanson on Themistocles in “No Glory That Was Greece” in What If?, edited by Robert Cowley