Thomas Ricks was making an interesting point about deficiencies in U.S. training of Afghan recruits in a Foreign Policy note and rhetorically asked, “ How many of the Spartans at Thermopalye were literate? . . . The average private soldier in Afghanistan does not need to be literate.”
I don’t wish to weigh in on the answer to the latter statement (it’s debatable, cf the “hay foot/”straw foot” terms used by Civil War and WWI rural doughboy recruits), but in fact the answer to his former question might be “actually, quite a lot of them.”
The status of ancient literacy in Greece is controversial, but I think both sides in the dispute would suggest the answer hinges on class and status — and the 300 at Thermopylae were among the most privileged of Spartan society. About the same time, during the Greek retreat to Salamis from Artemisium, Themistocles supposedly wrote detailed messages on cliffs above the straits, to encourage defection among the Ionians in Persian service (many of them the poorer who rowed in triremes), apparently in expectation that someone could read the epigraphs. Years ago I recall that Terrence Boring (Literacy in Ancient Sparta) studied the question in depth and I think concluded that Spartans, especially the Peers, might have been far more literate than we frequently think.