After a long journey into Persia battle is joined, Cyrus is killed in battle and the Greeks, (outnumbered, leaderless and in enemy territory) have to march back to Greece--fighting the whole damn way. This is one of my "desert island" books and I never tire of it.
I incorporate some of the Greek and Persian troop types into my own games. It gives opponents a "flavor" and makes for interesting PC choices besides the standard medieval "armored tank" fighter. I give you...the Peltast!