 Complete the following phrase:  In technological innovation, the early toe loop stirrup is credited to the cultures of India, and may have been in use as early as 500 BC. Not long after, the cultures of Mesopotamia and Ancient Greece clashed with those of central Asia and India. Herodotus 484425 BC wrote that Gandarian mercenaries of the Achaemenid Empire were recruited into the army of emperor Xerxes I of Persia 486465 BC, which he led against the Greeks. A century later, the Men of the Mountain Land, from north of Kabul River, served in the army of Darius III of Persia when he fought against Alexander the Great at 