The Greek, and previous to that, the Achean, were constantly placed into "situations" ( for lack of a better word. The gods toyed with the people incessantly ) where they were faced with Irony, or an impossibility of victory.
The perennial "no win" situation, as it were.
Leonidas was one of 2 kings of Sparta. He inherited the throne due to death in the famuily. He was traditionally a Military man. In order for him to save Sparta from the Persian Army, he basically had to break the law and violate the Carnia. The oracle had prophesied that either the King would die, or that Sparta would burn. But they did not share this information with Leonidas. He knew nothing of the propechy. He was simply told that the Army of Sparta was to remain in Sparta, and that ther would be no war during the Carnia.
Sparta was a city without walls, unlike places like Troy, which could withstand attack for many years. Sparta relied on it's own army for defense.
Knowing that, the King theorized that if the Spartan Army had to stand against the Persian forces at the present troop strength, that they were doomed. So, he chose to take 300 of his best, and try to head them off at the pass, so to speak. Although they were nowhere near Sparta, they probably would have eventually made it there, had Leonidas not done what he did. He bloodied them badly, and along with the Naval Victory of Salamis, and Xerxes departure with half of his forces prior to the the battle of Plateaa,
that the Spartans would have met the Persians in Sparta, and probably faced devastation.
The pouint being, that in order to be a true Spartan warrior, he had to disobey the oracle and make a stand. His actions and the actions of some of the other forces there are what saved Sparta, becuase, not only did it demoralize the Persians, and give the Greeks time to organize, but it sent a message to Xerxes, that basically, the Spartans were able to kick his lame butt all over Greece, regardless of what the Medes did.
The statement he made at the opening of the battle is clear. Molon, meaning "come" and Labe, meaning "get". "Come get some!" "Bring it on!"
Any number of phrases that have been uttered by people who are ready to kick butt and take names. That's the meaning of it. Come get what you deserve. No matter how you look at it, his actions, and the actions of his fellow Spartan and Thespian brothers is what saved Greece. Most of our modern medicine, philosophy, and beasic democratic ideas came from Greece. Greece that could just as easily have been Mede. Greece, that could have been the doorway to Europe. These guy helped change history, and made history in the process. Most of us can only pray that we are so lucky.