Persian Empire
Q & A 6 min read

Why Did Xerxes Invade Greece in 480 BCE?

Three reasons, working together. The most direct was the unfinished business of the reign of Darius I: the Persian expedition of 490 BCE had been defeated at Marathon, and the prestige of the Achaemenid state had suffered accordingly. Darius had begun planning a much larger campaign against Greece, and he died in 486 BCE before the plan could be carried out. His son Xerxes inherited the project. The second was the long-running conflict with the Greek world that had begun with the Ionian revolt of 499 BCE. The third was the strategic and economic logic of settling the Greek question at a moment when the dynasty was at the height of its resources and the western satrapies were still under firm control. The Greek tradition, beginning with Herodotus, attributed the invasion to a complex mix of personal ambition, family honour, and Persian imperial pride. Modern historians emphasise the strategic and economic dimensions. The standard modern treatment is Pierre Briant, From Cyrus to Alexander (2002), chapter 13.

The unfinished business of Darius

The most direct cause was the unfinished business of the reign of Darius I. The Persian expedition of 490 BCE, the Battle of Marathon, had been a serious humiliation: the punitive expedition against Athens and Eretria had been defeated by a small Athenian force on the plain of Marathon, and the prestige of the Achaemenid state had suffered accordingly. Darius, who had been planning a much larger campaign against Greece, did not live to lead it: he died in 486 BCE, after a reign of thirty-six years, leaving the expedition to his son and successor.

For the Greeks, the idea that Persia would return was a constant anxiety. The Athenians, in particular, had been bracing themselves for a second Persian invasion since Marathon, and they had used the decade between 490 and 480 BCE to build up their fleet and to prepare their defences. Themistocles persuaded the Athenians to use the newly discovered silver of the Laurion mines to build a fleet of 200 triremes, on the grounds that Athens would need a powerful navy to face the Persian threat. The Greek preparations were a direct response to the expectation of a renewed Persian campaign, and they reflect the seriousness with which the Greek world took the threat.

The strategic and economic dimensions

The Achaemenid state had been in conflict with the Greek world, in some form, since the Ionian revolt of 499 BCE, and the question was not whether to fight but how. The Greek cities of the Aegean, in particular, were a constant source of friction: they were nominally subject to Persia, but they were restive, and their support for the Ionian revolt had demonstrated that they could not be trusted. A second expedition, designed to settle the Greek question once and for all, was therefore a reasonable enterprise from the Persian point of view.

The economic dimension was equally important. The Aegean was a rich commercial region, and the Greek cities were a source of administrative talent, mercenary soldiers, and cultural prestige. A successful invasion would have given the Achaemenid state control of the Aegean, allowed it to project power into the eastern Mediterranean, and brought the rich cities of mainland Greece into the Persian orbit. The expedition was a project of imperial expansion designed to extend the Achaemenid state to the natural limits of the eastern Mediterranean world.

The preparations

The preparations for the invasion were on an unprecedented scale. According to Herodotus, the Persian army numbered more than two and a half million men, supplied by a fleet of more than 1,200 triremes. The modern consensus is that the numbers are exaggerated; a realistic estimate would put the army at perhaps 70,000 to 100,000 men, and the fleet at perhaps 600 to 800 triremes. W. Kendrick Pritchett’s The Greek State at War (vol. V, 1991) is the most thorough demolition of Herodotus’ figures. The army was drawn from every nation of the Achaemenid empire, and the fleet was drawn from the maritime subjects.

The logistics of the expedition required massive preparation. The Persians built a double pontoon bridge across the Hellespont, the narrow strait that separates Europe from Asia, to allow the army to cross. Herodotus describes an earlier pair of bridges (one of ships, one of boats) that was destroyed by a storm, after which Xerxes in a rage ordered the Hellespont to be whipped with three hundred lashes and a pair of fetters to be thrown into the sea; the destruction of the second pair of bridges is what provokes the whipping. A new bridge was constructed, and the army crossed. The Persians also dug a canal through the isthmus of Mount Athos, to allow the fleet to avoid the dangerous waters around the peninsula, and they stockpiled provisions along the line of march.

The crossing

The army crossed the Hellespont in 480 BCE on the double pontoon bridge, lashed together by cables of flax and papyrus. According to Herodotus, the crossing took seven days and seven nights, and the army was so large that it drank the rivers dry. From the Hellespont, the army marched through Thrace and Macedonia, joined by contingents from the northern Greek tribes, and reached Thermopylae in central Greece in the late summer of 480 BCE. The Persian fleet, meanwhile, sailed around the coast of the Aegean and took up position off the coast of Artemisium, on the northern coast of Euboea, opposite the Greek fleet.

The expedition was, in its scale and ambition, one of the largest military undertakings of the ancient world, and it dwarfed anything that the Greek world had ever seen. The preparations alone had taken several years, and the cost had been enormous. The expedition was a test of the Achaemenid state’s ability to project power at long range, and a test of the Greek world’s ability to resist.

The battles and the aftermath

The Persian invasion of 480 BCE was the occasion of three of the celebrated battles in the history of the ancient world. At Thermopylae, a small Greek force under the Spartan king Leonidas held the narrow coastal pass against the much larger Persian army for several days, before a local Greek betrayed the existence of a path around the position. The Greeks were surrounded and overwhelmed, and the 300 Spartans were killed to a man. At Salamis, in late September 480 BCE, the Greek fleet under Themistocles won a decisive naval victory in the narrow waters of the Bay of Salamis, sinking or capturing more than 200 Persian ships and effectively destroying the Persian fleet. At Plataea, in August 479 BCE, the combined Greek army under the Spartan regent Pausanias won a decisive land battle against the Persian army of Mardonius, breaking the Persian hold on mainland Greece.

The battles marked the end of the Persian invasion of Greece, and they have acquired a symbolic significance in Western memory that is far greater than their immediate strategic importance. The Greek victory was, in the long term, a victory for the Greek experiment in city-state democracy. The Persian state, however, was far from broken, and the Achaemenid dynasty would continue to rule for another 150 years. The real long-term consequence of the invasion was not the fall of the Persian Empire, but the rise of the Athenian Empire in the Aegean, and the long rivalry between the Greek world and the Persian world that would shape the subsequent history of the ancient Mediterranean.

The aftermath was, in the short term, a Persian withdrawal from mainland Greece, and a long period of relative peace between Persia and the Greek city-states. The peace of Callias, traditionally dated to 449 BCE (though many modern scholars treat the Peace of Callias as a later invention or 5th-century fiction), fixed the frontier of Persian influence in the Aegean at the coast of Asia Minor, and the two powers settled into a long rivalry that would last until the conquests of Alexander the Great. The invasion of 480 BCE marked a turning point in the history of the Achaemenid state and the beginning of a new phase in the relations between the Greek world and the Persian world.

Reading

  • Herodotus, The Histories, books 7–9, in Robin Waterfield’s translation (1998)
  • Briant, Pierre. From Cyrus to Alexander (2002), chapter 13
  • Wiesehöfer, Josef. Ancient Persia (1996), chapter 6
  • Pritchett, W. Kendrick. The Greek State at War, vol. V (1991)
  • Holland, Tom. Persian Fire: The First World Empire and the Battle for the West (2005)
  • Wallinga, H. T. The Persian Wars and the Ancient Greek Navy (in Dutch, 2005)