Pentecontaetia
Pentecontaetia (, "the period of fifty years") is the term used to refer to the period in Ancient Greek history between the defeat of the second Persian invasion of Greece at Plataea in 479 BC and the beginning of the Peloponnesian War in 431 BC. The term originated with a scholiast commenting on Thucydides, who used it in their description of the period. The Pentecontaetia was marked by the rise of Athens as the dominant state in the Greek world and by the rise of Athenian democracy, a period also known as Golden Age of Athens. Since Thucydides focused his account on these developments, the term is generally used when discussing developments in and involving Athens. Shortly after the Greek victory of 479 BC, Athens assumed the leadership of the Delian League, a coalition of states that wished to continue the war against Persia. This league experienced a number of successes and was soon established as the dominant military force of the Aegean. Athenian control over the league grew as some "allies" were reduced to the status of tribute-paying subjects and by the middle of the 5th century BC (the league treasury was moved from Delos to Athens in 454