Peter Green writes:
In 545 BCE – immediately after the conquest of Lydia by Cyrus, the aggressive and imperially expansive young king of Persia – the Greeks of Asia Minor, who had previously lived under the easy-going rule of Croesus the Lydian, and had received a sharp rebuff when they tried to get a similar deal from Cyrus, approached the Spartans for a protective alliance. The Spartans, notoriously shy of overseas commitments, refused their request; but they did, Herodotus tells us, send a diplomatic mission to Sardis. Its purpose was ‘to deliver a proclamation of the Lacedaemonians, warning Cyrus against harming any city on Hellenic soil, since this they would not overlook’. Cyrus’s reaction, when the diktat reached him, was to ask who on earth, and how numerous, these Lacedaemonians might be, that they dared to address him in such terms.