Answer by Kai Ruffing
Actually, that is a very good question which has worried modern researchers for a long time. Reading Herodotus, the answer would be that the origin of the conflict between the Persians and the Greeks goes back to the time of the Ionian Revolt. The Milesian tyrant Aristagoras first sought help for fighting against the Persians in Sparta, but the Spartan king Kleomenes denied any support of the Ionians since he thought that it would be impossible for the Spartans to campaign in the Persian realm and to attack Susa, even though Aristagoras promised a rich booty. At the end of the day, it was Kleomenes’ little daughter Gorgo who prevented her father from waging war against the Persians because she saw that the undertaking was risky and that the Spartans would be fighting for an unjust cause (5.51).
While Gorgo proved a wise adviser to the Spartans, the Athenians did not act wisely at all. When Aristagoras turned to them, believing in his promises of a rich booty, the Athenian assembly decreed to support the Ionian Revolt (5.97). With the help of the Athenians, the insurgents succeeded in taking Sardis, which was almost completely destroyed. According to Herodotus, then, the Great King Darius made war against the Greeks to take vengeance against the Athenians and Eretrians for supporting the revolt. Indeed, Herodotus greatly emphasizes the emotional dimension of Darius’ decision by relating how at every dinner Darius had a slave remind him that he should exact vengeance against Athens (5.105).
The campaign against Athens and Eretria led by Datis and Artaphernes in 490 BCE, however, was a failure for the Persians, who were defeated at the Battle of Marathon. After Darius’ death, his successor Xerxes was expected to continue the war and complete what his father left unfinished. Still, the young king was clearly hesitant to campaign against Greece. Nevertheless, according to Herodotus he had some disturbing dreams in which he was incited by a god to start the campaign, which he finally did after some discussions with his advisers (7.5-19).
So, in a nutshell, according to Herodotus it was revenge and the will of the divine which pushed the Persians to campaign against Greece. Scholars have given different interpretations, however, as to the ‘real reasons’ of Darius and Xerxes’ Western campaigns. It is generally agreed that they should be understood as part of the grand expansionist strategy of the Achaemenid empire. Some others have argued that Darius, who came to power through a conspiracy – as attested by Herodotus and the Behistun Inscription – and soon faced a huge number of revolts, needed a great military success to legitimize his kingship. The same is somehow true for Xerxes, who succeeded Darius without being his eldest son. It has also been suggested that Xerxes’ campaign was a pre-emptive strike against the rising sea power of Athens. This last interpretation is quite difficult to accept, however, as it projects unlikely geopolitical dynamics typical of contemporary nation-states onto the ancient Persian empire.
A much better interpretation has recently been put forward which sees Xerxes’ campaign as a parallel to imperial warfare in the Ancient Near East. Indeed, the campaign might have dealt with troubles in the Aegean theatre caused by Greek polities and their aristocrats. Consequently, the Aegean was seen by Darius and Xerxes as a borderland of their empire for which the Great King guaranteed order and peace. This leads to the conclusion that the Persian expedition to Hellas was intended as a campaign which included punitive actions against people violating the order of the empire (i.e. the Greeks, especially the Athenians) and which displayed triumphal achievements, and thus the heroism of the king as well as his divine favour.
All in all, there is no easy answer to the question, not least because every approach is freighted with methodological difficulties. An especially important one is, to what extent can the Greek literary sources be taken at face value concerning Persian motives for waging war in the Aegean and in Greece? Indeed, the sources from the Achaemenid empire – not least Persian royal inscriptions – do not mention the campaigns at all.
Bibliography:
J.O. Hyland, Xerxes’ Greek Spectacles and the Royal Campaign Tradition, in: P. Funke, G. Németh, A. Patay-Horváth, J. Wiesehöfer (ed.), Xerxes against Hellas. An Iconic Conflict from Different Perspectives, Stuttgart 2025 (Oriens et Occidens 44), 33-49.
H. Klinkott, Der Großkönig und das Meer: Achaimenidisches Reichsverständnis in einem neuen Weltbild, in: id., A. Luther, J. Wiesehöfer (eds.), Beiträge zur Geschichte und Kultur des alten Iran und benachbarter Gebiete. Festschrift für Rüdiger Schmitt, Stuttgart 2021 (Oriens et Occidens 36), 111-136.
M. Meier, The Greek World, in: B. Jacobs, R. Rollinger (eds.), A Companion to the Achaemenid Persian Empire Vol. I, Hoboken 2021, 623-637.
R. Rollinger, The Persian Empire in Contact with the world, in: K. Radner, N. Moeller, D.T. Potts (eds.), The Oxford History of the Ancient Near East Vol. V. The Age of Persia, Oxford 2023, 887-948.
R. Schulz, Zwischen Eroberungskrieg und Präventivschlag? Neue Perspektiven zu den Perserkriegen und ihren Voraussetzungen, Historische Zeitschrift 306 (2018), 667-684.
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