After the Persian failure at Marathon, King Darius planned revenge on the opposing empire, however, died in 486 BC. Succeeding the throne was his son Xerxes who set out to advance with Darius’ planned invasion of Greece. Xerxes planned his attack with new strategies, combining both a land and sea offence. As this would require a large army accompanied by a supportive and communicative navy, this logistical exercise took nearly four years to prepare. Hearing of Xerxes planned invasion in just 481 BC simultaneously resulted in a quick development of the Greek war force, instructed mainly by the Hellenic League and Themistocles.
As Herodotus