Note: the content of this post has been modified from its original version for clarity and accuracy.

I have a book on my current reading list called
Where History was Made. It is heavily biased, favoring Western civilization, and so naturally starts with the Greeks. In recounting the battle of Thermopylae, the book only tells about one-third of the tale but adds some juicy bits that I did not know previously. Here is a short lesson on what actually happened--as far as we can sensibly deduce--for all of you misinformed and Hollywood-stricken readers. If you hate lectures, avert your eyes now.
Persia was the largest empire in history until its time. After Darius failed one attempt to subdue Greece, and more directly the Athens, during the battle of Marathon (a story for another time), Xerxes, the next Persian emperor, thought he would teach the Athens a lesson for humiliating his father. Thus, they came to Greece.
The Greeks lived divided into city-states and fought amongst themselves as much as with outsiders. The Spartans, warriors of
Lacedaemon,
possessed a particularly brutal and militant culture, very much the black sheep of the Greeks, but were loyal to the death. They formed part of a small alliance that opposed Xerxes. The non-alliance cities either sold their allegance to Peria or stood on the sideline.
To stop the Persians, a small force of infantry, including several hundred of Sparta's elite troops, and a fleet of ships were sent to stop up the way. Thermopylae was to be the battlefield, chosen to take away the Persians' advantages of superior numbers and cavalry. (Thermopylae was in this way very similar to Marathon.) The battle lasted a few days while the Greeks used their long spears to slay and repel many of their enemies. Meanwhile, the small Greek navy ambushed the impressive Persian fleet, and with some luck and bad weather the Persian forces never landed on the beach to surround the Greek infantry.
The battle came to a head after a local man sold his secretes to Xerxes and lead Persian troops on a route to bypass the narrow beach. The Greeks had warning that their enemies would soon surround them and evacuated most of their forces, leaving only Leonidas, King of Sparta, with 300 Spartans and 700 Thespians. You see, before leaving for battle, Leonidas spoke with a prophetess who told him that if he went to battle he would not come back but would be remembered as a legend for all of time. He chose to stay and fight to the death. In doing so, he bought the Greeks a few more hours to rally themselves and, after the sac of Athens, another decisive naval victory, and several other battles, the Greeks did repel the invaders. The battle itself was an important event; the death of the King of Sparta and his men was mostly pointless. They did however set an example of dedication and sacrifice for the rest of Greece.
So why do we care? Well, eventually the Greeks united themselves and popularized democracy as practiced in Athens. Hurray for democracy. The end.
Not quite, actually. I learned two new
tid-bits. One of the monuments at Thermopylae pays tribute to the brave Thespians: a statue of Eros, the patron god of
Thespiae. Guess what English word we get from Eros? I'll give you a hint: my parents would be embarrassed if I said it in public. I also learned that the width of the passage at Thermopylae is no longer measured in meters, as during the historic battle, but in kilometers. That's geology for you. Apparently the sea has thrown up some earth in the past 2,500 years.