As he was tall and strong, and a very good athlete, he soon won the admiration of the Spartans, and made many friends. During his stay here, he heard that he had been tried at Athens, although absent, found guilty of sacrilege, and even sentenced to death.

This ingratitude on the part of his people so angered Alcibiades, that he told the Spartans all the Athenian plans, and showed how to upset them. By his advice, the Spartans sent aid to the Greeks in Sicily, helped them to resist the Athenian attack, and even captured both generals and seven thousand soldiers, who were put to death.