The circumstances under which the appeal was made were the following.  A new power had suddenly risen up in Asia.  About B.C. 558, ten years after Nebuchadnezzar’s subjection of Egypt, Cyrus, son of Cambyses, the tributary monarch of Persia under the Medes, assumed an independent position and began a career of conquest.  Having made himself master of a large portion of the country of Elam, he assumed the title of “King of Ansan,” and engaged in a long war with Astyages (Istivegu), his former suzerain, which terminated (in B.C. 549) in his taking the Median monarch prisoner and succeeding to his dominions.  It was at once recognized through Asia that a new peril had arisen.  The Medes, a mountain people of great physical strength and remarkable bravery, had for about a century been regarded as the most powerful people of Western Asia.  They had now been overthrown and conquered by a still more powerful mountain race.  That race had at its head an energetic and enterprising prince, who was in the full vigour of youth, and fired evidently with a high ambition.  His position was naturally felt as a direct menace by the neighbouring states of Babylon and Lydia, whose royal families were interconnected.  Croesus of Lydia was the first to take alarm and to devise measures for his own security.  He formed the conception of a grand league between the principal powers whom the rise of Persia threatened, for mutual defence against the common enemy; and, in furtherance of this design, sent, in B.C. 547, an embassy to Egypt, and another to Babylon, proposing a close alliance between the three countries.  Amasis had to determine whether he would maintain his subjection to Babylon and refuse the offer; or, by accepting it, declare himself a wholly independent monarch.  He learnt by the embassy, if he did not know it before that Nabonadius, the Babylonian monarch, was in difficulties, and could not resent his action.  He might probably think that, under the circumstances, Nabonadius would regard his joining the league as a friendly, rather than an unfriendly, proceeding.  At any rate, the balance of advantage seemed to him on the side of complying with the request of Croesus.  Croesus was lord of Asia Minor, and it was only by his permission that the Ionian and Carian mercenaries, on whom the throne of the Pharaohs now mainly depended, could be recruited and maintained at their proper strength.  It would not do to offend so important a personage; and accordingly Amasis came into the proposed alliance, and pledged himself to send assistance to whichever of his two confederates should be first attacked.  Conversely, they no doubt pledged themselves to him; but the remote position of Egypt rendered it extremely improbable that they would be called upon to redeem their pledges.