In 546 B.C, the Persians conquered Ionia. The Ionians revolted and Athens sent ships and soldiers to help. Even though the Persians had won, Darius the Great swore to get revenge on Athenians for aiding the Ionians which led to the Battle of Marathon.
Vowing to get revenge, the Persians attacked the Athenians in 490 B.C. on Marathon. Although the Athenians were greatly outnumbered, the Persians wore light armor and lacked training in land combat. After several hours, the Persians fled.
After the Athenians won the Battle of Marathon, Pheidippides was chosen to run 26 miles back to Athens and announce that they have won. Not long after, he collapsed and died.
In 480 B.C., Darius' son, Xerxes wanted to carry on his father's legacy by attacking Athens. When Xerxes reached Thermopylae, he was met with 7,000 Greeks including 300 Spartans. The Greeks stopped the Persians for three days.
The 300 Spartans stayed to fight back the Persians after the other Greek soldiers had retreated. The Spartans sacrificed themselves, while none survived the battle.
Themistocles convinced the Athenians to evacuate the city and fight in a small channel. Xerxes sent ships to block both ends of the channel, but the ships had trouble turning. Armed Athenians with battering rams punctured holes in the hulls of the ships as Xerxes watch more the 1/3 of his fleet sink.