The larger part of Elam, which went by the name of Anzan, had been seized by the Persians in the closing days of the Assyrian empire, and a line of kings of Persian origin had taken the place of the old sovereigns of Shushan.
Cyrus II., who was still but a youth, was now on the throne of Anzan, and, like his predecessors, acknowledged as his liege-lord the Scythian king of Ekbatana, Istuvegu or Astyages.

His first act was to defeat and dethrone his suzerain, in B.C.549, and so make himself master of Media.
A year or two later he obtained possession of Persia, and a war with Lydia in B.C.545 led to the conquest of Asia Minor.

Nabonidos had doubtless looked on with satisfaction while the Scythian power was being overthrown, and had taken advantage of its fall to rebuild the temple of the Moon-god at Harran, which had been destroyed by the Scythians fifty-four years before.

But his eyes were opened by the conquest of his ally the King of Lydia, and he accordingly began to prepare for a war which he saw was inevitable.

The camp was fixed near Sippara, towards the northern boundary of Babylonia, and every effort was made to put the country into a state of defence.
Cyrus, however, was assisted by the disaffected party in Babylonia itself, amongst whose members must doubtless be included the Jewish exiles.