Ancient Battles Deluxe Expansion Kit 2: Hell's Horsemen

From the publisher's website: They rode swiftly across Eurasia over steppe and across plains under the Great Khan, or from Byzantium in armor as Cataphracts. Man, beast, and bow has long been a weapon of shock and maneuver. Now you can find out as you re-write the pages of history's great battles like those featuring massive Persian cavalry formations at Thymbra (547 BC) and Platea (479 BC).