WHY THE 300 : Battle of Thermopylae

In the Battle of Thermopylae of 480 BC an alliance of Greek city-states fought the invading Persian army in the mountain pass, Thermopylae. Vastly outnumbered, the Greeks held back the enemy in one of the most famous last stands of history. A small force led by king Leonidas of Sparta blocked the only road through which the massive army of Xerxes I could pass. After several days of confrontation the Persians attacked but were defeated by heavy losses, disproportionate to those of the Greeks. This continued on the second day but on the the third day of the battle a local resident named Ephialtes betrayed a mountain path that led behind the Greek lines. With the rest of the army dismissed king Leonidas stayed behind with his 300 Spartans bodyguard and the 700 man Thespian army even though they knew it was pure suicide, to allow the rest of the army to escape.
The disproportionate losses of the Persian army alarmed Xerxes so that when his navy was later defeated at the Salamis he fled Greece leaving only part of his force to finish the job of the conquest of Greece, that was defeated at the battle of Plataea. The performance of the defenders at the battle of Thermopylae is often used as an example of the advantages of training, equipment and good use of terrain to maximise an army's potential, as well as a symbol of courage against extremely overwhelming odds. The heroic sacrifice of the Spartans and the Thespians has captured the minds of many throughout the ages and has given birth to many cultural references as a result.

There is an epitaph on a monument at site of the battle (which was erected in 1955) with Simonides' epigram, which can be found in Herodotus' work The Histories (7.228), to the Spartans:

Ω ξειν', αγγέλλειν Λακεδαιμονίοις ότι τάδε
(O xein', angellein Lakedaimoniois hoti têde)
κείμεθα τοις κείνων ρήμασι πειθόμενοι.
(keimetha tois keinon rhémasi peithomenoi.)

Which to keep the poetic context can be translated as:
Go tell the Spartans, stranger passing by,
that here, obedient to their laws, we lie

Herodotus wrote that when Dienekes, a Spartan soldier, was informed that Persian arrows were so numerous that they blotted out the sun, he remarked with characteristically laconic prose,

"So much the better, we shall fight in the shade."