The order of his conquests is not traceable; but it is clear that after his conquest of the Lydian empire (about B.C.

554) he proceeded eastward, with the special object of subduing Bactria.43 To reach Bactria, he would have to pass through, or close by, Parthia.

Since, as Herodotus says, "he conquered the whole way, as he went," we may fairly conclude that on his road to Bactria he subjugated the Parthians.

It was thus, almost certainly, that they lost their independence and became Persian subjects.

Competent enough to maintain themselves against the comparatively small tribes in their near neighborhood, the Chorasmians, Hyrcanians, Arians of Herat, Bactrians, and Sagartians, it was not possible for them to make an effectual resistance to a monarch who brought against them the entire force of a mighty empire.