According to Ctesias, he was scarcely seated upon the throne, when he led an expedition to the far north-east against the renowned Bactrians and Sacans; and at any rate, whether this be true or no--and most probably it is an anticipation of later occurrences--it is certain that, instead of folding his hands, Cyrus proceeded with scarcely a pause on a long career of conquest, devoting his whole life to the carrying out of his plans of aggression, and leaving a portion of his schemes, which were too extensive for one life to realize, as a legacy to his successor.

The quarter to which he really first turned his attention seems to have been the north-west.

There, in the somewhat narrow but most fertile tract between the river Halys and the Egean Sea, was a state which seemed likely to give him trouble--a state which had successfully resisted all the efforts of the Medes to reduce it, and which recently, under a warlike prince, had shown a remarkable power of expansion.

An instinct of danger warned the scarce firmly-settled monarch to fix his eye at once upon Lydia; in the wealthy and successful Croesus, the Lydian king, he saw one whom dynastic interests might naturally lead to espouse the quarrel of the conquered Mede, and whose power and personal qualities rendered him a really formidable rival.
The Lydian monarch, on his side, did not scruple to challenge a contest.
The long strife which his father had waged with the great Cyaxares had terminated in a close alliance, cemented by a marriage, which made Croesus and Astyages brothers.

The friendship of the great power of Western Asia, secured by this union, had set Lydia free to pursue a policy of self-aggrandizement in her own immediate, neighborhood.
Rapidly, one after another, the kingdoms of Asia Minor had been reduced; and, excepting the mountain districts of Lycia and Cilicia, all Asia within the Halys now owned the sway of the Lydian king.