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". Plutarch states that Cimon struck a power-sharing deal with his opponents, according to which Pericles would carry through the interior affairs and Cimon would be the leader of the Athenian army, campaigning abroad. If it were actually made, this bargain would constitute a concession on Pericles' part that he was not a great strategist. Kagan's view is that Cimon adapted himself to the new conditions and promoted a political marriage between Periclean liberals and Cimonian conservatives. In the mid-450s the Athenians launched an unsuccessful attempt to aid an Egyptian revolt against Persia, which led to a prolonged siege of a Persian fortress in the Nile Delta. The campaign culminated in disaster; the besieging force was defeated and destroyed. In 451–450 BC the