Answer: For ancient Greece, the empire that was the closest to them and also always tried to conquer them was the Persian Empire.
Explanation: When we look at the history of ancient Greece, we see that in the 6th-4th centuries B.C, Persia bothered Greece in order to conquer them. Some famous battles that the Persians and the Greeks fought were:
- The Battle of Thermopylae: You might know this battle as the "300 Spartans"
- The Battle of Marathon: Pheidippides ran a whole marathon to tell Athens the victory against King Darius I of Persia.
- The Battle of Salamis: An epic navy battle in which the Greeks crushed the Persians at the Peloponnesian peninsula using Greece's geography.