The Achaemenid Empire was more than just the first great Persian empire; for under the rule of the Teispids (i.e. the kings before Darius I) and the Achaemenids (from Darius I), it unified for the first time all of the Near and Middle East and then kept it together, mostly in peace. It lasted from c. 550 (conquest of the Median kingdom) until 330 BC, when it was itself conquered by…