The Greek Wars
The Greeks, especially the Ionians, rebelled against the Persian rulers who had taken them over after the Persian Cyrus defeated the Lydian King Croesus. King Darius I of Persia swore to punish for himself, and the uprisings were at first successful. He re-established his absolute control over Ionia after defeating the army Miletus and putting down the revolt in 493 BC.
Darius sent advisers to Greece at the same time. Sparta and Athens refused and killed the Persian advisers as a signal of spite although most of the smaller states agreed. Darius, mad at the Greek abuse moved on to the plain of Marathon near Athens. Spartans stopped leaving, because the message arrived during a religious festival. The message was about the Atheanian leaders sent to Sparta for aid. Nevertheless, the Athenian army, under Miltiades, won an awesome victory over a Persian army three times as large, and the Persians left Greece.