 The two most important Greek cities, the Ionian-democratic Athens and the Dorian-aristocratic Sparta, led the successful defense of Greece against the invading Persians from the east, but then clashed against each other for supremacy in the Peloponnesian War.The Kingdom of Macedon took advantage of the following instability and established a single rule over Greece.Desire to form a universal monarchy brought Alexander the Great to annex the entire Persian Empire and begin a hellenization of the Macedonian possessions.