Around 550 B.C.E. the Persian people--who were previously practically unknown in the annals of history--emerged from their base in southern Iran (Fars) and engaged in a monumental adventure that, under the leadership of Cyrus the Great and his successors, culminated in the creation of an immense Empire that stretched from central Asia to Upper Egypt, from the Indus to the Danube. The Persian (or Achaemenid, named for its reigning dynasty) Empire...