Example how the quote by Ariel Durant, "A great civilization is not conquered from without until it has destroyed itself from within" applies to Ancient Greece.

The correct answer to this open question is the following.

The quote by Ariel Durant, "A great civilization is not conquered from without until it has destroyed itself from within," applies to Ancient Greece. in the following way.

It is true that it is difficult to defeat you from the outside until you break from the inside. That is what happened to Ancient Greece. The best example could be the Peloponnesian War.

Two of the most powerful city-states of ancient Greece couldn't solve their many differences in a pacific way, and they fight each other -we the support of their allies- in the Peloponnesian War. Athens fought Sparta, and although Sparta won the war, the pain, destruction, and suffering left by the war, weakened ancient Greece and made it vulnerable against its enemies.

probally   a few days after there called