Achaemenid ruler Cyrus the Great conquered Sogdiana while campaigning in Central Asia in 546–539 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 invasion of Greece in 480 BC. A Persian inscription from Susa claims that the palace there was adorned with lapis lazuli and carnelian originating from Sogdiana.