Athens’ role in the Median Wars and her contribution to the Greek victory over the Persians established her position as the power that could best guarantee peace and freedom in the Aegean. During the period known as the Fifty-year period many Greek cities allied themselves with Athens in recognition of her strength to form the Delian League (478/7 B.C.).

The emergence of Athens as the most important economic and political centre in the Aegean influenced internal political developments. The reforms of Ephialtes (462/1 B.C.) and Pericles (451/0 B.C.), for example, contributed to the development of some of the most important features of Athenian democracy. As for external affairs, Athens’ expansionism caused resentment among the allied cities, and prepared the ground for the Peloponnesian War, in which Athens and Sparta clashed, drawing their allies into the conflict. The progressive erosion of Athenian power during the last phase of the war following the failed Sicilian expedition (415-3 B.C.) temporarily undermined the faith of Athenians in their democratic constitution, prompting two oligarchic reforms (411/0 B.C. and 404/3 B.C.).

Economic recovery at the beginning of the 4^th century B.C., enabled Athens to re-establish her hegemony to some extent (387/7 B.C.). Under Demosthenes’ leadership, Athens tried (unsuccessfully) to unite the forces of southern Greek cities against a new threat, that of Philip of Macedon. Athenian defeat at Chaeronea (338 B.C.) redefined the balance of power in Greece, with Macedonia asserting its military, political and economic supremacy.