History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
The King, it is said, marvelled at his purpose[*](Or, as some take it, character. cf. τὸ φρόνημα καὶ τὴν τόλμαν αὐτοῦPlut. Them. 28, the boldness of his spirit.) and bade him do as he desired. And Themistocles, in the interval of his waiting, made himself acquainted, as far as he could, with the Persian language and with the customs of the country;
but when the year was ended he came to the King and becme more influential with him than any of the Hellenes ever had been before, both because of the reputation he already enjoyed and of the hope which he kept suggesting to him that he would make all Hellas subject to him, but most of all in consequence of the insight he minifested, of which he gave repeated proofs.
I[cr indeed Themistocles was a man who had most convincingly demonstrated the strength of his natural sagacity, and was in the very highest degree worthy of admiration in that respect. For by native insight, not reinforced by earlier or later study,[*](i.e. without knowledge acquired either before or after the occasion for action had arisen.) he was beyond other men, with the briefest deliberation, both a shrewd judge of the immediate present and wise in forecasting what would happen in the most distant future. Moreover, he had the ability to expound to others the enterprises he had in hand, and on those which he had not yet essayed he could yet without fail pass competent judgment; and he could most clearly foresee the issue for better or worse that lay in the still dim future. To sum up all in a word, by force of native sagacity and because of the brief preparation he required, he proved himself the ablest of all men instantly to hit upon the right expedient.
He died a natural death, an illness taking him off, though some say that he put an end to his own life by poison[*](For the various accounts, see Cic. Brut. 11. 43; Plut. Them. 31; Diod. 11.58; Ar. Eq. 83.) when he realised it to be impossible to fulfil his promises to the King.