Cleon held the political scene of Athens after Pericles's death, during the first years of the Peloponnesian War. Ruling a city endangered byfnvasion, victorious of the best spartan soldiers at Pylos in 425 B.C., killed in actidn a few years later, Cleon didn't know posterity of his renowned predecessor though. On the contrary, a real 'black legend' was established around him which wentthrough the ages: contemporary authorities like Thucydides or Aristophanes and also later writers -Ancients like Moderns- introduced him as a corrupt, venal and coarse character, as a demagogue who skilfully flattered the people and who was in favour of an immoderate imperialism and excessive war. This book intends to re-evaluate Cleon's political work, especially compared with Pericles's, whose ambitions hardly differed: preservation of the empire -and not extension of it-, reinforcement of democratic rights set up during the former period -and not political 'radicalization'-, continuation of the war according to Pericles's strategy and aims - and not exaggerated warmongering. In this work, ideological or moral bias, often conveyed by ancient sources, has been left aside and the specific context of Athens (which was involved in a terrible war to protect its imperial and democratic integrity at the end of the fifth century B.C.) has been reconstructed, which allows us to consider Cleon as a Jess dark historie character than what tradition passed on.