Cyrus, King of Persia (559-530 bc), who in under a quarter-century built an empire from the Mediterranean to central Asia. A four-year war (553-550) in which with modest resources and huge persistence Cyrus displaced Astyages of Media, gave him western Iran, and by 547 he had expanded into eastern Anatolia and northern Mesopotamia. Responding to Lydian aggression, Cyrus fought an indecisive battle (Pteria), then captured Sardis by siege (547-546). In an even briefer campaign (but with a pre-established bridgehead in the Diyala basin) Cyrus crossed the Tigris and captured Babylon within fifteen days (539). Some in Babylon saw his victory as desirable (for religious reasons) but their substantive contribution is unknown. Cyrus eventually died in central Asia on a frontier whose establishment involved extensive undocumented conflicts (545-540, 538-530). There is no explicit evidence for the nature of his army or the tactical/strategic details of his campaigns. He profited from treachery, could move fast, and was good at sieges, but his huge success might suggest more profound innovations. Xenophon saw him that way, but independent confirmation is lacking.
— Christopher Tuplin
