The military history of Greece between the end of the second Persian invasion of Greece and the Peloponnesian War (479–431 BC) is not well supported by surviving ancient sources. This period, sometimes referred to as the "pentekontaetia" ("πεντηκονταετία", "the Fifty Years") by ancient writers, was a period of relative peace and prosperity within Greece. The richest source for the period, and also the most contemporaneous, is Thucydides' "History of the Peloponnesian War", which is generally considered by modern historians to be a reliable primary account. Thucydides only mentions this period in a digression on the growth of Athenian power in the run up to the Peloponnesian War, and the account is brief, probably selective and lacks any dates. Nevertheless, Thucydides's account can be, and is, used by historians to draw up a skeleton chronology for the period, on to which details from archaeological records and other writers can be superimposed.