In 494 BC, Argos suffered a crushing defeat at the hands of its regional rival, Sparta, at the Battle of Sepeia. Following this defeat, Herodotus tells us the city suffered a form of "stasis". The political chaos is thought to have resulted in a democratic transition in the city. Argos did not participate in the Hellenic Alliance against the Persian Invasion of 480 BC. This resulted in a period of diplomatic isolation, although there is evidence of an Argive alliance with Tegea prior to 462 BC.