A conquest that did not happen
The title promises a tale of conquest, but the Persian conquest of mainland Greece never took place. The Persian kings did burn Athens and did push deep into Greece in 480 BCE, yet within two years their land and sea forces had been beaten and the invaders had withdrawn. The Persian Empire itself remained enormous and wealthy afterwards. What ended was its attempt to add the Greek mainland, which is why the story reads best as one of Persian failure there, set against a much larger imperial background.
The conflict is often called the Greco-Persian conflict by modern historians, and it is usually dated from the Ionian Revolt of 499 BCE to the Greek victories of 479 BCE, with fighting around the Aegean continuing for some years afterwards.
Sources and their limits
Nearly everything we know about the narrative comes from Herodotus, a Greek writing a generation or so later, with some support from Thucydides, later writers such as Plutarch, and a small number of inscriptions and archaeological finds. Persian royal inscriptions say very little about these campaigns. This matters: the account is told from the Greek side, and some of its details, especially the numbers, are doubted.
Herodotus gives enormous figures for Xerxes’ army. Modern scholars generally think the real numbers were far smaller, though they disagree about how much smaller. It is safer to say that the Persian force was very large for its time and leave it there.
Background: an empire meets the Greek world
Under rulers such as Cyrus the Great, Persia grew within a few decades from a regional kingdom into an empire stretching from Anatolia to Central Asia. Cyrus took over the Lydian kingdom around the middle of the sixth century BCE, and with it the Greek cities of western Anatolia, known as Ionia. These cities were governed through local rulers under the wider satrapy system, with tribute owed to the Persian king.
Resentment in some of these cities, tied to local politics and to the rulers Persia supported, set the stage for revolt.
The Ionian Revolt, 499 to 493 BCE
The Ionian Revolt began in 499 BCE. Athens and Eretria sent a small force to help, and Greek and allied troops took part in burning Sardis, the satrapal centre, in about 498 BCE. Persia responded by retaking the revolting regions piece by piece. The decisive naval defeat of the Ionians at Lade, in about 494 BCE, was followed by the destruction of Miletus. By 493 BCE the revolt was over.
Herodotus presents the Athenian role at Sardis as one reason Darius I later turned on mainland Greece. Historians also point to a plain imperial logic: a Persian king who held the Aegean coast and its islands might reasonably want to secure the other side of the sea.
The first invasion: Marathon, 490 BCE
A Persian expedition under Datis and Artaphernes crossed the Aegean in 490 BCE, took Eretria, and landed at Marathon in Attica. The Athenians, joined by a contingent from Plataea, attacked and won. The details of the engagement belong to the separate account of the Battle of Marathon, but the outcome is clear: the Persians withdrew without conquering Athens. Marathon was a setback for Persia rather than a disaster for the empire, and Darius began preparing a larger effort. He died in 486 BCE before launching it.
The second invasion: Xerxes, 480 to 479 BCE
Xerxes, Darius’ son, spent several years on preparation. Ships were gathered from Phoenician city-states and other subjects, a canal was dug across the Athos peninsula, and bridges of boats were built across the Hellespont. Many Greek states chose not to resist at all; others formed an alliance led militarily by Sparta, with Athens providing the largest fleet.
The main stages were:
- Thermopylae and Artemisium (480 BCE). A small Greek force held the pass at Thermopylae for a few days while the fleet fought indecisively off Euboea. The pass was turned by a mountain path, and the Greeks withdrew. Athens was evacuated and then burned.
- Salamis (480 BCE). The Greek fleet fought the Persian navy in the narrow waters beside Athens and won a decisive victory. The role of Themistocles naval strategy is covered in its own article.
- Plataea and Mycale (479 BCE). A combined Greek army defeated the Persian land force left under Mardonius at Plataea in Boeotia. Greek tradition places a further Greek victory over Persian forces at Mycale, on the Anatolian coast, at around the same time, though the exact sequence is debated.
Without command of the sea, the Persian army in Greece could not be supplied indefinitely. This logistical problem, rather than any single heroic stand, did much to decide the war.
What changed afterwards
Victory strengthened the confidence of Athens in particular. In 478 or 477 BCE, many Aegean Greeks formed an alliance that later became the Athenian-led league, whose Delian League tribute helped fund a navy and, eventually, Athenian dominance. The war thus shaped the politics of the fifth-century golden age as much as it shaped the Persian frontier.
Persia did not vanish from Greek affairs. Persian officials and money remained a factor in Greek diplomacy for generations, and the Greek cities of Asia Minor were back under Persian authority by the early fourth century BCE. The empire finally fell not to Greek city-states but to Macedonian forces under Alexander, a story told in the account of Gaugamela.
Why the title is only half right
“Conquest” fits the earlier Persian record in Lydia, Babylon and Egypt. In Greece, the campaigns ended in withdrawal. Treating them as a Persian failure, rather than a Persian conquest, is closer to what the sources show, while remembering that the sources are mostly Greek and that the Persian view is largely lost.