In 546 BC the Persian king Darius the great defeated the Ionian Greeks and then vowed to destroy Athens in revenge, He sent ships and soldiers over to defeat Athens. they revolted because the Persians had settled in the conquered area that they wanted.
The Persian fleet carried 25,000 men across the Aegean sea and landed northeast of Athens on a pain called Marathon, 10,000 Athenians waited for the battle, Greeks charged first, Persians fled the battlefield and the Persians lost over 6,000 men while the Athenians only had around 200 men. the Persians won the battle because the Athenians fled.
The Athenians won a battle they didn't realize they had won, there was a young man that they had chosen to run 26 miles to bring the good news to Athens, His name was Pheidippides. He needed to tell the Athenians news about them winning the battle they had previously been in.
After 10 years Xerxies assembled an invasion force against Athens, Some city-states agreed to fight the Persians, They marched down the eastern coast of Greece
Some Greeks fought on the Persian side of the battle. 7,000 Greeks including 300 Spartans blocked the way of Xerxies from passing to attack. Greeks had stopped them for three days, there was a man they ran into that told them a secret path around the mountain to attack from behind, the Spartans sacrificed and all were killed.
Athens positioned their fleet in a narrow channel near the island of Salamis. Xerxies sent his warships to block both ends of the channel. more than 1/3 of Xerxies fleet sunk.