On the death of Laborosoarchod the conspirators selected one of their number, a certain Nabonadius or Nabannidochus, and invested him with the sovereignty.  He was in no way related to the late monarch, and his claim to succeed must have been derived mainly from the part which he had played in the conspiracy.  But still he was a personage of some rank, for his father had, like Neriglissar, held the important office of Rab Mag.  It is probable that one of his first steps on ascending the throne was to connect himself by marriage with the royal house which had preceded him in the kingdom.  Either the mother of the late king Laborosoarchod, and widow of Neriglissar, or possibly some other daughter of Nebuchadnezzar, was found willing to unite her fortune with those of the new sovereign, and share the dangers and the dignity of his position.  Such a union strengthened the hold of the reigning monarch on the allegiance of his subjects, and tended still more to add stability to his dynasty.  For as the issue of such a marriage would join in one the claims of both royal houses, he would be sure to receive the support of all parties in the state.  Very shortly after the accession of Nabonadius (B.C. 555) he received an embassy from the far north-west.  An important revolution had occurred on the eastern frontier of Babylonia three years before, in the reign of Neriglissar; but its effects only now began to make themselves felt among the neighboring nations.  Had Cyrus, on taking the crown, adopted the policy of Astyages, the substitution of Persia for Media as the ruling Arian nation would have been a matter of small account.  But there can be little doubt that he really entered at once on a career of conquest, Lydia, at any rate, felt herself menaced by the new power, and seeing the danger which threatened the other monarchies of the time, if they allowed the great Arian kingdom to attack them severally with her full force, proposed a league whereby the common enemy might, she thought, be resisted with success.  Ambassadors seem to have been sent from Sardis to Babylon in the very year in which Nabonadius became king.  He therefore had at once to decide whether he would embrace the offer made him, and uniting with Lydia and Egypt in a league against Persia, make that power his enemy, or refuse the proffered alliance and trust to the gratitude of Cyrus for the future security of his kingdom.  It would be easy to imagine the arguments pro and contra which presented themselves to his mind at this conjuncture; but as they would be destitute of a historical foundation, it is perhaps best to state simply the decision at which he is known to have arrived.  This was an acceptance of the Lydian offer.  Nabonadius consented to join the proposed league; and a treaty was probably soon afterwards concluded between the three powers whereby they united in an alliance offensive and defensive against the Persians.