Pericles' joy at the unexpected return of his father had to compete in his emotions with ever-heightening fear about the threat approaching their homeland from Persia. As King Xerxes in 480 marched southward from Macedonia toward central Greece, scouts constantly carried news of his progress to the Greek communities on his invasion route. The Greeks who had sent him tokens of submission were confident that they would not be attacked (though they might be bankrupted by the demand to supply provisions to his army and navy). On the other hand, those who had defied Xerxes' order to submit were terrified. What if some of their compatriots now changed their minds and went over to the side of the Persian king, begging for his mercy and pointing out their fellow citizens who opposed “cooperation”? But, they asked themselves, what if they, too, gave up their fight to preserve their city-state's political liberty before any blood was shed; could they then strike a deal with Xerxes for lenient treatment? After all, everyone remembered, once the rebellious Ionian Greeks had been pacified and returned to the fold as Persian subjects, Xerxes' father, Darius, had installed democracies to govern them instead of tyrannies, thereby giving the citizens control over their domestic politics.

As they could practically hear the footfalls of the unimaginably numerous enemy army approaching their borders, the Greeks who had not given earth and water to the Great King faced a life-and-death decision. It is remarkable that in the end any members at all of this anti-Persian alliance of Greek states stood fast against such seemingly overwhelming odds; that they experienced grave doubts and dissension the whole time only underlines the amazing nature of their commitment to fight to preserve their political liberty. The Athenians, or at least the majority of them, supported the decision to oppose Xerxes, even though, as events would show, they had another tempting option if they were willing to make a deal with him.

In 480 Pericles was approaching fifteen years old – an age at which he would have been following his male relatives around during this time of ultimate peril and listening in on their heated discussions as the news grew steadily worse.