Since the whole expedition was a punitive one, intended to crush the Athenians in retaliation for supporting the Ionian revolt and did not in any way involve a larger conquest of Hellas itself, this isn't the usual thread asking what an Achaemenid Greece would look like. Rather, say, what if the Achaemenids won at Marathon, defeated the Spartan reinforcements afterwards, and went straight into Athens, completely slaughtering the population and carting off a significant portion as slaves back to Asia, and destroying the city for supporting the Ionian revolt, sending a powerful message into the hearts of several more Greek cities. It did somewhat happen IOTL, during the second invasion, but the main citizen body of Athens had escaped, with Athens itself defended very sparsely, with the Acropolis as a citadel. While sailing back across the Aegean, a massive storm wrecks the returning fleet, downing Datis, most of the army, and most of the loot and slaves, where they get shipwrecked on a number of islands and get slaughtered. While Darius still dies and Xerxes still faces rebellions in Babylonia and Egypt, he attempts another conquest anyway, although IOTL he wanted to avenge Marathon and finish what his father started, here, he will think that they would be weak and make an easy conquest, but he fails, while personally leading the troops in an alt-Salamis, false rumours of his death lead to a general rout, and the pontoon bridges near the Hellespont are attacked and nearly destroyed. Xerxes still retreats as OTL, to deal with yet another Babylonian revolt, as said rumours spread further into Asia Minor and soon Mesopotamia and the heart of the empire. What would be interesting, is how is Classical Greece changed as a result of an Athens severely curtailed in power and influence? It would definitely be refounded, but I don't think it would ever reach the heights it did previously? What changes result?