People of Greece. I have been sent by King Darius I of Persia. I implore you to accept Persian authority.
Meanwhile in Sparta...
Get out of our Sparta, Persian scum!
Go and spread our message to the Greek city-states. Avoid Athens and Sparta.
480 BCE - Xerxes invades Greece
King Darius I of Persia sent heralds to Greek cities to get the people to accept Persian authority because he saw them as a threat to his empire.
Xerxes confronts Leonidas
Surrender, Leonidas! Drop your weapons!
This movement offended the Greeks, but many agreed in an effort to save themselves. However, the Athenians and the Spartans memorably refused. Their people went as far as to throw heralds into wells and pits.
In 480 BCE, Darius I's successor, Xerxes, invaded Greece as a continuation of his predecessor's plan. He sent heralds to many Greek cites except for Athens and Sparta because of their previous reactions. Many city-states joined or remained neutral
Before he invaded, Xerxes urged the Spartan king, Leonidas, to surrender his arms. Leonidas famously refused and the Persian army invaded.
"Come and take them" Molon Labe
The Persians quickly moved overland from Dardanelles with a supplemental fleet following along the coast. They quickly overcame the north of Greece and moved south. The Greeks tried to halt the Persian army on land in a narrow pass at Thermopylae and in the straits of Artemisium.
The Greek army was at a large disadvantage as they were facing an army of around 70,000-300,000 men with 7,000 men. And despite this, they were able to hold their position. They held a line that was only a few dozen yards long which constricted the battlefield and prevented the Persians from utilizing their numbers.