(478 BC) an association of about 150 Greek Polis (city-states), under the leadership of Athens, their purpose was to continue fighting in the Persian War after the Battle of Plataea. Athenians took over the leadership of the Greek world by forming a defensive alliance against the Persians called the Delian League. Under the leadership of the Athenians, the Delian League pursued the attack against the Persian Empire. By controlling the Delian League, Athens had created an empire.