Sources

The primary source for the Greco-Persian Wars is the Greek historian Herodotus. The Sicilian historian Diodorus Siculus, writing in the 1st century BC in his Bibliotheca historica, also provides an account of the Greco-Persian wars, partially derived from the earlier Greek historian Ephorus. This account is fairly consistent with Herodotus'. The Greco-Persian wars are also described in less detail by a number of other ancient historians including Plutarch, Ctesias of Cnidus, and are referred to by other authors, as in Aeschylus in The Persians.

Archaeological evidence, such as the Serpent Column (now in the Hippodrome of Constantinople), also supports some of Herodotus' specific claims. 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. For example, the military strategist Sir Basil Henry Liddell Hart defers to Grundy. Grundy also explored Plataea and wrote a treatise on that battle.

On the Battle of Thermopylae itself, two principal sources, Herodotus' and Simonides' accounts, survive. In fact, Herodotus' account of the battle, in Book VII of his Histories, is such an important source that Paul Cartledge wrote: "we either write a history of Thermopylae with [Herodotus], or not at all". Also surviving is an epitome of the account of Ctesias', by the eighth-century Byzantine Photias, though this is "almost worse than useless", missing key events in the battle such as the betrayal of Ephialtes, and the account of Diodorus Siculus' in his Universal History. Diodorus' account seems to have been based on that of Ephorus and contains one significant deviation from Herodotus' account: a supposed night attack against the Persian camp, of which modern scholars have tended to be skeptical.

• 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.

RESOURCES
This article uses material from the Wikipedia article "Battle of Thermopylae", which is released under the Creative Commons Attribution-Share-Alike License 3.0.