History of the Peloponnesian War

But when Phrynichus saw that there would be a proposal for the recall of Alcibiades, and that the Athenians would accede to it, being afraid, on considering the opposite tendency of what had been maintained by himself, that if he were restored he would do him some mischief, as one who had impeded his plans, he had recourse to the following device.

He sent to Astyochus the Lacedaemonian admiral, who was still in the neighbourhood of Miletus, with secret instructions that Alcibiades was ruining their cause by bringing Tissaphernes into friendship with the Athenians; expressly mentioning all the other matters also, and pleading that it was pardonable in him to devise evil against a man who was an enemy, even though it were to the detriment of the state.

Now Astyochus did not so much as think of punishing Alcibiades—especially as he no longer put himself in his power as he used to do—but having gone up to him and Tissaphernes at Magnesia, at once told them the contents of the letter from Samos, acting as an informer to them, and for his own private gain devoting himself, as was said, to the interest of Tissaphernes both on these and on all other matters:

for which reason also he was the more gentle in remonstrating with him respecting the pay not being given in full.

Alcibiades immediately sent a letter to Samos giving information against Phrynichus to the authorities there, telling them what he had done, and requiring that he should be put to death. Phrynichus, being confounded and in the most extreme danger, sent again to Astyochus, reproaching him because his former information had not been duly kept secret, and telling him now that he was prepared to give them an opportunity of destroying the whole Athenian armament at Samos; describing the particulars of the way in which he could do it, as Samos was unfortified; and pleading that it was not now culpable in him, being, as he was, in danger of his life through them, to do this, or any thing else, rather than be destroyed by his bitterest enemies. Astyochus gave information of this also to Alcibiades.