In 546 BC the Persians (gray armor people) conquered the sea. The wars began in ionia and the ionians revolt, Athens sends ships to support the revolt. Daris the great (Persian king) defeats the revolt and vows to destroy Athens in revenge.
Thermopylece and salamis
In 490 BC Persian fleat of 25,000 men rode across the Aegean sea and landed in marathon. There are 10,000 Athenians waiting for the persians to attack. During this battle the Persians lost 6,000 men and Athens lost 200 men.
Delian league
mean while Athens stood defenseless. They choose a young runner named Pheidippides to bring back the good news that Athens won the battle, and to make sure Athenians would not give up the city. Pheidippides races 26.2 miles to deliver this good news but then sadly dies.
Consequences of Persian war
In 480 BC Darius the Greats son Xerxes assembles and the Greeks are now badly divided. Some city-states supported the Athenians and others didn't. Xerxes came to a narrow mountain pass while 7,000 Greeks (including 300 spartens) blocked the way. The Greeks stopped the advance for 3 days meanwhile Athens fights at sea. Xerxes then sets fire to Athens and then sends war ships to block both ends.
The delion league is an alliance to defeat the persions. It was between two city-states and was led by Athens. The delion league successfully driven the persians out.
When the war was over the city-states felt free and confident especially Athens. In the 470's Athens leads the delion league but Athens used it's power to control league members. In time these city-states become little more than provinces of Athens.