 Complete the following phrase:  Achaemenid ruler Cyrus the Great conquered Sogdiana while campaigning in Central Asia in 546539 BC, a fact mentioned by the ancient Greek historian Herodotus in his Histories. Darius I introduced the Aramaic writing system and coin currency to Central Asia, in addition to incorporating Sogdians into his standing army as regular soldiers and cavalrymen. A contingent of Sogdian soldiers fought in the main army of Xerxes I during his second, ultimately-failed 