The difference here is that the Sparta of this world is far from the elite fighting force they envision themselves as.
IRON has the tech advantage, the numbers, real war-experience, and the willpower for a prolonged conflict.
These are Spartans in name only. I'm going to enjoy watching you mop the floor with them.
Get ready to join your beloved coward Hellas, Sparta. Down in the IRON meat grinder.