Answer :
I hope one of these helps sorry if they dont
cemented Pan-Hellenic identity, saw cooperation on an unprecedented scale, showed Greek military superiority over the Persians. Athens emerged as the rivals of Sparta for military prestige.
The Battle of Marathon was significant because it proved to the Greeks that the Persians were not 'invincible', which boosted the moral of the Greek troops, increasing their confidence to incline themselves in a common cause if the Persian attacked again (which I believe they would).
Battle of Marathon, (September 490 bce), in the Greco-Persian Wars, decisive battle fought on the Marathon plain of northeastern Attica in which the Athenians, in a single afternoon, repulsed the first Persian invasion of Greece.
The significance of the battle for Western Civilization
While the Battle of Thermopylae was technically a defeat for the Greeks, it was also a victory in the long run because it marked the beginning of several important Greek victories against the Persians and boosted the morale of all the Greek city-states