With this name is called the period of about half a century between the taking of Sesto and the Peloponnesian war. During the Pentecontaetia the effects of the victories with which the Greeks had weakened the Persian offensive took place. These victories not only guaranteed the Greeks safety from the Persians, who in fact never renewed their attacks on the Balkan Peninsula, but gave the victors full awareness of their strength and the value of their political and military systems, based on freedom. small town. Hence the self-confidence, the superb contrast between Greeks and barbarians, the new intensity of political movements, the audacity that pervaded the entire spiritual life of the Greek people during the century. V. A preponderant part in the new development played the Athenians. Immediately after the capture of Sesto and the liberation of the colonies of Asia, since the war had by now transformed from land to sea and since the liberated cities felt much closer affinity with the Athenians than with the Spartans, the Greeks islands and coasts of Asia and Thrace broke away from the Spartan league and offered hegemony to the Athenians. In this way the Delian League was formed, an imposing federal organism, the largest and most solid that Greece had seen up to then, founded on the full autonomy of the Confederates in internal affairs and on the equality of all in deliberating around the common interests in a diet that was to meet in Delos. Here too the contributions paid by the allies for the war were collected in the federal treasury. The Athenians held the presidency of the league and the direction of the military enterprises decided by the diet. As long as the memory of Persian servitude and the war of liberation was alive and as long as the offensive against Persia continued, the league remained solid and compact. The vigor of the democratic movement in Greece contributed to its compactness, for a large part of the century. V, due both to the dissolution of the old oligarchies due to the changed economic and social conditions, and to the greater self-awareness that the classes had acquired, which with the spear and the oar had won the war for independence. The democratic movement was established even in the Peloponnese, despite the fact that there the oligarchies could count on the support of Sparta. But Sparta managed to tame it because the Athenians, still tied to her by the memory of their common victories, they did not dare take the side of Peloponnesian democracy. In Athens itself, moreover, in the first years after the Persian wars, the consequences that came from the changed conditions had not yet been fully drawn, and the property class, headed by Aristide and Cimon, still retained its dominance. In those years Cimon acquired the favor of the people with his military exploits and particularly with the great victory he won in 470-69 at the mouth of the Eurimedonte in Pamphylia over the Persian army, which was apparently preparing to enter the Aegean. And Themistocles, who with a more far-sighted policy foresaw and prepared the fight against Sparta, first ostracized, then condemned in absentia for treason, had to flee to Persia (464). L’ support given to Sparta against the rebellious Messenians, in evident contradiction with the interests of Athens and with the democratic spirit of its population, ended with the exhaustion of Cimon and leading radical democracy, led by Ephialtes and Pericles (462-61). Assassinated shortly after Ephialtes, Pericles remained at the head of Athens and was uncrowned king for about thirty years, with no other powers than those that constitutionally gave him the position of stratego, to which he was elected from year to year, always ready to return to private life at the first vote against the assembly. In possession of this authority founded on the consent of all, but in fact almost absolute, he has full responsibility for the direction that Athenian and political policies followed up to the first years of the Peloponnesian war. use that the Athenian people made of their forces, then in full bloom. Inside, Pericles promoted radical democracy, with the development he gave to the people’s courts, in which the jurors were recruited for the most part from the poorer class. Outside he tried, with the help of a broad democratic propaganda, to undermine the prestige and Spartan hegemony. At the same time he resumed the fight against Persia in Egypt with the utmost vigor, trying to win it over to Greek civilization and expansion and thus anticipating the work that the Ptolemies later accomplished there. But, although the memory of the national war prevented the cooperation between Sparta and Persia that was later possible in the Peloponnesian war, despite the boundless audacity that Athens showed in those years, which were truly the years of its greatest greatness, it found itself unable to sustain the double war against Persia and the Peloponnesian league. In Greece the Athenians, after a long siege, took possession of Aegina, and, defeated at Tanagra but victors at Enofita (457), they subjected Boeotia to their hegemony. The enterprise of Egypt, however, not carried out with sufficient forces, ended with a catastrophe of the Athenian fleet, comparable in its size and effects to the Sicilian catastrophe of 413. Under the impression of this triumph of the barbarians, Sparta, instead of taking advantage of it to resume the fight against Athens more vigorously, he granted a five-year truce, and Athens used it to vigorously renew the war against Persia, under the leadership of Cimon. He led an expedition in the island of Cyprus (450), where he died of the plague without being able to weaken the Persian resistance on the island. The victory at Salamis of Cyprus (449), with which the Athenian army opened the way back, only served to prepare an honorable peace between Athens and Persia (448), which however left Cyprus to the Persians. At the resumption of the war in Greece, however, Athens was still in an inferior condition, having not been able to remedy the disasters suffered, and so, although under the leadership of Pericles it managed to recover the rebelled Euboea (446), it lost Boeotia and the other regions of central Greece, over which it had affirmed its superiority; and he had to settle for these losses with the thirty-year peace which ended shortly after (445).