Riace bronzes – The Greek Warriors. Image taken from Wikipedia
How do you tell your troops you shouldn’t be scared of a super power everybody is terrified of? You show them naked. That is what the Spartan King Agesilaus did. At Ephesus, while Persian prisoners were being sold as slaves (another way to finance his army) he gave the order to have their clothes taken off. The Persians used a lot of mercenaries (even Greeks) to fight their wars, and they were not as keen as the Greeks (and especially the Spartans) on exercising and training all the time. Once the Persian prisoners were naked, Agesilaus told his troops “Look at these people, they look like pale nerds that play videogames all day, and these are the people you are afraid of!” For the Greeks that was a revelation, they were like “wow, no kidding, check out those weak lousy wimps!”*
To the Persians did was humiliating to the next level as they did not have a tradition of showing themselves naked. The Greeks on the other hand would compete in wrestling and running events naked, and they would strip off their clothes on any occasion they deemed suitable, even at a gravestone(!): According to Plutarch, Alexander the Great ran naked with his companions at the gravestone of Achilles, as it was customary to do.
*or in the words of Plutarch: “…but their naked bodies, which were utterly white and delicate, owing to their effeminate habits, were ridiculed useless and worthless”