Periclean strategy
Early years: Pericles was born c. 495 BC, in Athens, Greece. He was the son of the politician Xanthippus, who, though ostracized in 485–484 BC, returned to Athens to command the Athenian contingent in the Greek victory at Mycale just five years later. Pericles' mother, Agariste, was a member of the powerful and controversial noble family of the Alcmaeonidae, and her familial connections played a crucial role in helping start his political career. Agariste was the great-granddaughter of the tyrant of Sicyon, Cleisthenes, and the niece of the Athenian reformer Cleisthenes. Pericles belonged to the Attic phyle (clan) of Acamantis (Ἀκαμαντὶς φυλή). His early years were quiet; the introverted young Pericles avoided public appearances, instead preferring to devote his time to his studies.
According to Herodotus and Plutarch, Agariste dreamed, a few nights before Pericles' birth, that she had borne a lion. Legends say that Philip II of Macedon had a similar dream before the birth of his son, Alexander the Great. One interpretation of the dream treats the lion as a traditional symbol of greatness, but the story may also allude to the unusually large size of Pericles' skull, which became a popular target of contemporary comedians (who called him "Squill-head", after the squill or sea-onion). Although Plutarch claims that this deformity was the reason that Pericles was always depicted wearing a helmet, this is not the case; the helmet was actually the symbol of his official rank as strategos (general).

Our policy does not copy the laws of neighboring states; we are rather a pattern to others than imitators ourselves. It is called a democracy, because not the few but the many govern. If we look to the laws, they afford equal justice to all in their private differences; if to social standing, advancement in public life falls to reputation for capacity, class considerations not being allowed to interfere with merit; nor again does poverty bar the way, if a man is able to serve the state, he is not hindered by the obscurity of his condition.
His family's nobility and wealth allowed him to fully pursue his inclination toward education. He learned music from the masters of the time (Damon or Pythocleides could have been his teacher) and he is considered to have been the first politician to attribute importance to philosophy. He enjoyed the company of the philosophers Protagoras, Zeno of Elea, and Anaxagoras. Anaxagoras, in particular, became a close friend and influenced him greatly.
Pericles' manner of thought and rhetorical charisma may have possibly been in part products of Anaxagoras' emphasis on emotional calm in the face of trouble, and skepticism about divine phenomena. His proverbial calmness and self-control are also often regarded as products of Anaxagoras' influence.

Political career until 431 BC: 

Entering politics: In the spring of 472 BC, Pericles presented The Persians of Aeschylus at the Greater Dionysia as a liturgy, demonstrating that he was one of the wealthier men of Athens. Simon Hornblower has argued that Pericles' selection of this play, which presents a nostalgic picture of Themistocles' famous victory at Salamis, shows that the young politician was supporting Themistocles against his political opponent Cimon, whose faction succeeded in having Themistocles ostracized shortly afterward.
Plutarch says that Pericles stood first among the Athenians for forty years. If this was so, Pericles must have taken up a position of leadership by the early 460s BC –  in his early or mid-thirties. Throughout these years he endeavored to protect his privacy and to present himself as a model for his fellow citizens. For example, he would often avoid banquets, trying to be frugal.
In 463 BC, Pericles was the leading prosecutor of Cimon, the leader of the conservative faction who was accused of neglecting Athens' vital interests in Macedon. Although Cimon was acquitted, this confrontation proved that Pericles' major political opponent was vulnerable.

Ostracizing Cimon: Around 461 BC, the leadership of the democratic party decided it was time to take aim at the Areopagus, a traditional council controlled by the Athenian aristocracy, which had once been the most powerful body in the state. The leader of the party and mentor of Pericles, Ephialtes, proposed a reduction of the Areopagus' powers. The Ecclesia (the Athenian Assembly) adopted Ephialtes' proposal without opposition. This reform signaled the beginning of a new era of "radical democracy".
The democratic party gradually became dominant in Athenian politics, and Pericles seemed willing to follow a populist policy to cajole the public. According to Aristotle, Pericles' stance can be explained by the fact that his principal political opponent, Cimon, was both rich and generous, and was able to gain public favor by lavishly handing out portions of his sizable personal fortune. The historian Loren J. Samons II argues, however, that Pericles had enough resources to make a political mark by private means, had he so chosen.
In 461 BC, Pericles achieved the political elimination of this opponent using ostracism. The accusation was that Cimon betrayed his city by aiding Sparta.
After Cimon's ostracism, Pericles continued to promote a populist social policy. He first proposed a decree that permitted the poor to watch theatrical plays without paying, with the state covering the cost of their admission. With other decrees he lowered the property requirement for the archonship in 458–457 BC and bestowed generous wages on all citizens who served as jurymen in the Heliaia (the supreme court of Athens) some time just after 454 BC. His most controversial measure, however, was a law of 451 BC limiting Athenian citizenship to those of Athenian parentage on both sides.

Rather, the admiration of the present and succeeding ages will be ours, since we have not left our power without witness, but have shown it by mighty proofs; and far from needing a Homer for our panegyrist, or other of his craft whose verses might charm for the moment only for the impression which they gave to melt at the touch of fact, we have forced every sea and land to be the highway of our daring, and everywhere, whether for evil or for good, have left imperishable monuments behind us.
Such measures impelled Pericles' critics to hold him responsible for the gradual degeneration of the Athenian democracy. Constantine Paparrigopoulos, a major modern Greek historian, argues that Pericles sought for the expansion and stabilization of all democratic institutions. Accordingly, he enacted legislation granting the lower classes access to the political system and the public offices, from which they had previously been barred.
According to Samons, Pericles believed that it was necessary to raise the demos, in which he saw an untapped source of Athenian power and the crucial element of Athenian military dominance. (The fleet, backbone of Athenian power since the days of Themistocles, was manned almost entirely by members of the lower classes.)
Cimon, in contrast, apparently believed that no further free space for democratic evolution existed. He was certain that democracy had reached its peak and Pericles' reforms were leading to the stalemate of populism. According to Paparrigopoulos, history vindicated Cimon, because Athens, after Pericles' death, sank into the abyss of political turmoil and demagogy. Paparrigopoulos maintains that an unprecedented regression descended upon the city, whose glory perished as a result of Pericles' populist policies.
According to another historian, Justin Daniel King, radical democracy benefited people individually, but harmed the state. In contrast, Donald Kagan asserts that the democratic measures Pericles put into effect provided the basis for an unassailable political strength. After all, Cimon finally accepted the new democracy and did not oppose the citizenship law, after he returned from exile in 451 BC.

Leading Athens: Ephialtes' murder in 461 BC paved the way for Pericles to consolidate his authority. Without opposition after the expulsion of Cimon, the unchallengeable leader of the democratic party became the unchallengeable ruler of Athens. He remained in power until his death in 429 BC.

First Peloponnesian War: Pericles made his first military excursions during the First Peloponnesian War, which was caused in part by Athens' alliance with Megara and Argos and the subsequent reaction of Sparta. In 454 BC he attacked Sicyon and Acarnania. He then unsuccessfully tried to conquer Oeniadea on the Corinthian gulf, before returning to Athens. In 451 BC, Cimon returned from exile and negotiated a five years' truce with Sparta after a proposal of Pericles, an event which indicates a shift in Pericles' political strategy. Pericles may have realized the importance of Cimon's contribution during the ongoing conflicts against the Peloponnesians and the Persians. Anthony J. Podlecki argues, however, that Pericles' alleged change of position was invented by ancient writers to support "a tendentious view of Pericles' shiftiness".