The Persian War was a huge turning point in the history of Greece. When Persia attacked Greece, the city-states, many of which who were in the middle of mutual wars, banded together to fight Persia. Afterwards, the Delian League formed to protect against futher attacks caused more issues.
That's right! We used geography, strategy, and better equipment to destroy the Persians!
Oh no! Even with our great army with many times more people, we couldn't conquer the resilient Greeks in one swoop!
Thermopylae
The Peoloponnesian War was another great turning point the history. After Athens rose to power, Sparta challenged and defeated her. With Athens weakened, the city-states were freed from oppression. Eventually, Greece was divided and was conquered by Macedonia.
At the battle of Aegospotami, the Spartas surprised the weary Athenians and destroyed their entire navy.
Alexander's army staged a final battle after refusing to surrender, annihlating the remainder of Persia's troops and army.
Alexander the Great's campaign through Persia was a turning point because it ended Persia's long rule of Asia and Europe and started a new conquesting era, which crumbled after Alexander's death.