Sanctuary of Apollo at Delphi, aquarelle by Albert Tournaire (1862-1958) / 1894 (Modern period)
Upon the arrival of the Persians, the terrified Delphians consulted the Oracle of Apollo. They were told to address their prayers to the winds, as they would be Greece's most powerful ally in the coming conflict; Xerxes campaign did indeed rely heavily on coordination between land and sea forces advancing in unison.
During the Battle of Thermopylai, a storm cost the Persian sea armada many of its ships—over four hundred vessels were destroyed. In calm weather, these ships would likely have forced the Greeks to fight in a tactical retreat, letting Xerxes land troops south of Leonidas' position and bypass Thermopylai entirely. The cooperation of the winds led the Athenians to later construct a temple in honor of Boreas, the wind god.
Pictorial map of the Dardanelles, frontier between Europe and Asia / 1705 (Modern period)
The Greeks had always distinguished Europe—where they had settled—from Asia. They reckoned it began with the far side of the Aegean Sea and extended well beyond to Persia and India. But, beyond pure geography, the Persian invasion gave a political significance to the distinction between Asia and Europe.
Herodotos writes of two worlds: Asia, dominated by the Persian Empire, and Europe, by which he actually means the Greek world. This is particularly notable at the time of the passage of the Dardanelles by the Persian army.
While Greece is still a few hundreds of kilometers away, Herodotos quotes Xerxes as saying: "Let us enter into Europe after having prayed to the gods who reign over the land of the Persians". He passes radically from one world to another, from one civilization to the other. Texts describe Asia as a "barbarous country", but we must be careful that the word does not have the meaning of today; it simply means that the spoken language is incomprehensible to the Greeks, without implying a judgement of value.
In "The Iliad", Homer describes the struggles that broke out between friends and foes over who would lay claim to the remains of a fallen warrior. The death of Leonidas at Thermopylai prompted such a fight.
Herodotos, who knew "The Iliad" well, was no doubt aware that he was repeating a well-known trope. He says that two sons of Darius fell in fighting over Leonidas' corpse, and that a melee ensued between the Spartans and Persians. Leonidas' conduct at Thermopylai is comparable to the Homeric heroes of legend, as it's often suggested that this conflict is as important as the Trojan War itself.
Bust of Herodotos, Roman copy of a Greek original from the 5th-4th cent. BCE / 2nd. cent. CE (Roman period)
The Greco-Persian Wars incited the Greek Herotodos from Asia Minor to write the first works of a new literary genre: history. At the beginning of his book, Herodotos writes, "Herodotos exposes here his research, so that what men have accomplished does not fade from memory, those great and wonderful exploits accomplished by both Barbarians and Greeks".
The word "research" was previously used only in medicine to describe the search for the causes of a disease. It then came to designate a new intellectual construction, history, in the current sense of the word, highlighting the need for rigor and objectivity. Since the 5th century BCE, it's thanks to the Histories of Herodotos that we're able to understand the deeds of Sparta at Thermopylai.
Persian King, quiver over shoulder, in kneeling-running position, from a silver siglos from the time of Darius I-Xerxes / 490-485 BCE (Achaemenid period)
Xerxes went to spectacular lengths to ensure the passage of his army from Asia Minor into Greece. For example, he made a bridge of boats to cross the straits of Dardanelles, twelve kilometers long. This bridge was barely finished when a storm destroyed it. Furious, Xerxes ordered that the sea be punished with three hundred lashes, and the chains be thrown to the bottom of the ocean to better restrain it.
Xerxes also dug a canal at the entrance of the eastern peninsula of Athos, which has a height of more than 2,000 meters, can prove extremely dangerous in the event of a storm, as shown by the catastrophe that struck a Persian fleet in 492 BCE. Xerxes had a channel of some two kilometers long constructed, using "detachments of all the peoples of the army, and by the inhabitants of the region, who dug under the threat of the whip". Herodotos saw it as a manifestation of pride more than a work of public utility. It would've sufficed, he says, to build a kind of wooden rail on which the vessels would have been drawn, as was done for the Isthmus of Korinth.
