Event #1: Persia forces Greece to submit over its rule because of a land dispute. Athens and Sparta don't take it very well and the Persian War begins. The significance of this event is it started the Persian War, which would cause a latter effect on Hellas as a whole.
We will not surrender!!
Event #2: Battle of Marathon is a big part of the Persian War because it tells the story of how the Greeks defeated the Persians while being heavily outnumbered. And giving the rest of Greece confidence that they can win the war. This was significant because it gave the rest of Greece hope. Also, that really embarrassed Persia because they were supposed to be the better army.
Event #3: King Xerxes son of Darius invades Greece with 200,000-250,000 soldiers, 1,207 triremes, and 3,400 ships. They Invade Greece easily beating small armies on the way. The significance of this event is, Persia was going to try and claim Athens. Athens was a very important city-state in Greece and if Persia claimed it, the war might have come out different.
Event #4: Spartans stop the march of the Persians. King Leonidas of Sparta took 300 men to stop the Persians. He slaughtered thousands of the enemy to buy time for Athens to flee the city and warn the rest of Greece. This was significant because Sparta is not really known for helping and also this event became a war story for ages.
Event #5: The rest of the Persians that survived were forced to retreat or fight in the Battle of Platea. The rest of the Persians left for good. This event is significant because the Greeks kicked out the Persians for good and won the war. It also gave Greece unity.
Event #6: The Greeks after the Persian War formed an alliance with all the city states around the area in Greece called the Delian League. Athens soon dominated the Delian League. The significance of this event is Sparta because of Athens being head of the Delian League started a war against Athens called the Peloponnesian Wars. They both fought for 70 years until Sparta won. Because of the war, Greece was vulnerable and lost to the attacks from the Macedonians.