Background

The Greek city-states of Athens and Eretria had encouraged the unsuccessful Ionian Revolt against the Persian Empire of Darius I in 499–494 BC. The Persian Empire was still relatively young and prone to revolts amongst its subject peoples. Darius, moreover, was a usurper and had spent considerable time extinguishing revolts against his rule.

The Ionian revolt threatened the integrity of his empire, and Darius thus vowed to punish those involved, especially the Athenians, "since he was sure that [the Ionians] would not go unpunished for their rebellion". Darius also saw the opportunity to expand his empire into the fractious world of Ancient Greece. A preliminary expedition under Mardonius in 492 BC, to secure the land approaches to Greece, re-conquered Thrace and forced Macedon to become a client kingdom of Persia's.

A map of almost all the parts of the Greek world that partook in the Persian Wars

( Click image to enlarge)

Darius sent emissaries to all the Greek city-states in 491 BC asking for a gift of "earth and water" as tokens of their submission to him. Having had a demonstration of his power the previous year, the majority of Greek cities duly obliged. In Athens, however, the ambassadors were put on trial and then executed by throwing them in a pit; in Sparta, they were simply thrown down a well. This meant that Sparta was also effectively at war with Persia.

Darius thus put together an amphibious task force under Datis and Artaphernes in 490 BC, which attacked Naxos, before receiving the submission of the other Cycladic Islands. The task force then moved on Eretria, which it besieged and destroyed. Finally, it moved to attack Athens, landing at the bay of Marathon, where it was met by a heavily outnumbered Athenian army. At the ensuing Battle of Marathon, the Athenians won a remarkable victory, which resulted in the withdrawal of the Persian army to Asia.

Darius, therefore, began raising a huge new army with which he meant to completely subjugate Greece; however, in 486 BC, his Egyptian subjects revolted, indefinitely postponing any Greek expedition. Darius then died whilst preparing to march on Egypt, and the throne of Persia passed to his son Xerxes I. Xerxes crushed the Egyptian revolt and very quickly restarted the preparations for the invasion of Greece. Since this was to be a full-scale invasion, it required long-term planning, stockpiling, and conscription. Xerxes decided that the Hellespont would be bridged to allow his army to cross to Europe, and that a canal should be dug across the isthmus of Mount Athos (rounding which headland, a Persian fleet had been destroyed in 492 BC). These were both feats of exceptional ambition, which would have been beyond any other contemporary state. By early 480 BC, the preparations were complete, and the army which Xerxes had mustered at Sardis marched towards Europe, crossing the Hellespont on two pontoon bridges. According to Herodotus, Xerxes army was so large that, upon arriving at the banks of the Echeidorus River, his soldiers proceeded to drink it dry. In the face of such imposing numbers, many Greek cities capitulated to the Persian demand for a tribute of earth and water.

The Athenians had also been preparing for war with the Persians since the mid-480s BC, and in 482 BC the decision was taken, under the guidance of the Athenian politician Themistocles, to build a massive fleet of triremes that would be essential for the Greeks to fight the Persians. However, the Athenians lacked the manpower to fight on both land and sea; therefore, combating the Persians would require an alliance of Greek city-states. In 481 BC, Xerxes sent ambassadors around Greece requesting "earth and water" but very deliberately omitting Athens and Sparta. Support thus began to coalesce around these two leading states. A congress of city-states met at Corinth in late autumn of 481 BC, and a confederate alliance of Greek city-states was formed. It had the power to send envoys to request assistance and dispatch troops from the member states to defensive points, after joint consultation. This was remarkable for the disjointed Greek world, especially since many of the city-states in attendance were still technically at war with each other.

The "congress" met again in the spring of 480 BC. A Thessalian delegation suggested that the Greeks could muster in the narrow Vale of Tempe, on the borders of Thessaly, and thereby block Xerxes' advance. A force of 10,000 hoplites was dispatched to the Vale of Tempe, through which they believed the Persian army would have to pass. However, once there, being warned by Alexander I of Macedon that the vale could be bypassed through Sarantoporo Pass and that Xerxes' army was overwhelming, the Greeks retreated. Shortly afterwards, they received the news that Xerxes had crossed the Hellespont.

Themistocles, therefore, suggested a second strategy to the Greeks: the route to southern Greece (Boeotia, Attica, and the Peloponnesus) would require Xerxes' army to travel through the very narrow pass of Thermopylae, which could easily be blocked by the Greek hoplites, despite the overwhelming numbers of Persians. Furthermore, to prevent the Persians from bypassing Thermopylae by sea, the Athenian and allied navies could block the straits of Artemisium. Congress adopted this dual-pronged strategy. However, the Peloponnesian cities made fall-back plans to defend the Isthmus of Corinth, should it come to that, whilst the women and children of Athens had been evacuated en masse to the Peloponnesian city of Troezen.

Outline of the Battle of Thermopylae (480 BC)

HISTORIC BATTLES

Battle of Thermopylae (480 BC)

The Battle of Thermopylae was fought between an alliance of Greek city-states, led by King Leonidas of Sparta, and the Persian Empire of Xerxes I over the course of three days, during the second Persian invasion of Greece. View Historic Battle »

Sources: George B. Grundy was the first modern historian to do a thorough topographical survey of the narrow pass at Thermopylae, and to the extent that modern accounts of the battle differ from Herodotus' they usually follow Grundy's.

Background: Darius also saw the opportunity to expand his empire into the fractious world of Ancient Greece.

Prelude: Leonidas took with him the 300 men of the royal bodyguard, the Hippeis. This expedition was to try to gather as many other Greek soldiers along the way as possible and to await the arrival of the main Spartan army.

Strategic and tactical considerations: From a strategic point of view, by defending Thermopylae, the Greeks were making the best possible use of their forces. As long as they could prevent further a Persian advance into Greece, they had no need to seek a decisive battle and could, thus, remain on the defensive.

First day battle: First, he ordered 5,000 archers to fire a barrage of arrows, but they were ineffective; they fired from at least 100 yards away, according to modern day scholars, and the Greeks' bronze shields and helmets deflected the missile.

Second day battle: On the second day, Xerxes again sent in the infantry to attack the pass, "supposing that their enemies, being so few, were now disabled by wounds and could no longer resist." However, the Persians had no more success on the second day than on the first.

Third day battle: Upon discovering that his army had been encircled, Leonidas told his allies that they could leave if they wanted to. While many of the Greeks took him up on his offer and fled, around two thousand soldiers stayed behind to fight and die.

Aftermath: With Thermopylae now opened to the Persian army, the continuation of the blockade at Artemisium by the Greek fleet became irrelevant.

HISTORY

Battle of Thermopylae (480 BC)

The Battle of Thermopylae was fought between an alliance of Greek city-states, led by King Leonidas of Sparta, and the Persian Empire of Xerxes I over the course of three days, during the second Persian invasion of Greece.