What significant event is marked by the Battle of Thermopylae in 480 BC?

The Battle of Thermopylae in 480 BC is significant primarily because it showcased the heroic stand of King Leonidas and his 300 Spartan warriors against the vastly superior forces of the Persian Empire led by King Xerxes. This battle, although ultimately a tactical defeat for the Greeks, served as a pivotal moment in the larger context of the Greco-Persian Wars.

The valor and determination of Leonidas and his men delayed the advance of the Persian army, allowing other Greek city-states time to prepare for further confrontations and to ultimately regroup for subsequent battles, such as the Battle of Salamis. The stand at Thermopylae became emblematic of courage and sacrifice against overwhelming odds, inspiring future generations.

In contrast, the other options relate to different aspects of Greek and Persian history. The conquest of the Persian Empire is not accurate in this context, as the battle did not lead to the actual overthrow of the Persians. Although the Battle of Thermopylae was a symbol of Greek unity and resistance, it did not directly establish Greek democracy, which had its own distinct historical developments. The Persian War did not end with the Battle of Thermopylae; it continued until the eventual Greek victories at Salamis and Plataea