The battle of Thermopylae is still widely discussed today, thanks to the blockbuster film "300." The most important source on this topic is the 7th book of Herodotus' "Histories." It is essential for the study of ancient history, particularly the Persian Wars. The reader learns about the long preparations for war by the Persian king Xerxes and his massive campaign in 480 BC through Asia Minor, across the Bosporus, and through Northern and Central Greece, until he faces the Hellenes, led by the Spartans, at the narrow pass of Thermopylae. Hopelessly outnumbered, the Spartans march to certain death. Since this battle, their iron discipline has become legendary.