What impact did the outcome of the Persian war have on Athens

In the later stages of the war it led the Delian League to protect the cities against the Persians, taking financial contributions from the cities to maintain the fleet which protected them. When Persia finally agreed to stay away from the cities, Athens continued to collect the contributions from the cities and maintain a superior navy, and used the surplus to glorify the city and keep half its population on the public payroll, and using the war fleet to collect the funds by force if necessary, and effectively turning the League into an empire.

This, plus the walls it built around the city and its harbour, made Athens overconfident and interfering in other states, resulting in the Peloponnesian War in which the Greek world was devestated over 27 years, and a defeated Athens lost its empire and became a second rate power.