I'm getting mixed sources, where the Spartans actually a professional military at any time or where they the best soldiers of the Ancient Greek world? I'm getting a lot of sources saying the Spartans only became the best soldiers because of Thermopylae. I've read sources stating that the Spartan Agoge only became tougher as their name grew and they only became a disciplined unbreakable fighting force after Thermopylae, during the classical and Hellenistic eras, that they only became a warrior state after the stand of the 300. Is this true? Or where the sole Spartans always this disciplined phalanx that could not be wavered or broken, that would march in perfect step, quietly and slowly, due to their discipline. I understand that the Periokoi or the Helots would waver and flee, but what about the Spartans, the Homoioi, would they flee or stand their ground and never waver?
where they the best soldiers of the Ancient Greek world?
Yes, for a definition of 'soldier' that very much does not resemble the modern conception of the term, and in the same sense of the Spartans being a medium-sized fish in a very small pond. More can always be said on the matter; for the meantime, I recommend starting off with u/Iphikrates' post on the Spartan Mirage, which takes on some of your questions as posed, and for the rest, I recommend the good Doctor's flair profile for more than you'd ever thought you'd want to know about Classical Greek warfare.