Cleon in Harpers Dictionary of Classical Antiquities
（Κλέων). An Athenian, the son of a tanner, and said himself to have exercised that trade. Of extraordinary impudence and little courage, slow in the field, but forward and noisy in the assembly, corrupt, but boastful of integrity, and supported by a coarse but ready eloquence, he gained such consideration by flattering the lower orders that he became the head of a party. By an extraordinary train of circumstances he came off victorious in the affair of Sphacteria (q.v.), the Athenian populace having chosen him one of their generals. Elated upon this with the idea that he possessed military talents, he caused himself to be appointed commander of an expedition into Thrace. He was slain in a battle at Amphipolis against Brasidas, the Spartan general, B.C. 422.
It is probably unfortunate in the interest of historical truth that the accounts we have of Cleon's personality exist only in the writings of Thucydides and a partisan play, The Knights, of Aristophanes, both of whom were violently prejudiced against Cleon, the former personally and the latter politically. For some remarks on this head, see the history of Grote.
Cleon in Wikipedia
Cleon (Greek: Κλέων, sometimes Kleon) (d. 422 BCE) was an Athenian statesman and a Strategos during the Peloponnesian War. He was the first prominent representative of the commercial class in Athenian politics, although he was an aristocrat himself. Contemporaries Thucydides and Aristophanes represented him as a warmonger and a demagogue; modern historians provide a more balanced view.
Opposition to Pericles
Cleon first came to notice as an opponent of Pericles in the late 430s through his opposition to Pericles' strategy of refusing battle against the Peloponnesian League invaders in 431 BC. As a result, he found himself acting in concert with the Athenian aristocratic parties, who also had no liking for Pericles. During 430 BC, after the unsuccessful expedition by Pericles to the Peloponnesus, and when the city was devastated by the plague, Cleon headed the opposition to Pericles' rule. At this time, Pericles was accused by Cleon of maladministration of public money, with the result that Pericles was found guilty and removed from office (see Grote's History of Greece, abridged ed., 1907, p. 406, note 1). However, Pericles' setback was temporary and he was soon reinstated.
Rise in popularity
The death of Pericles from the plague in 429 BC left the field clear for new leadership in Athens. Hitherto Cleon had only been a vigorous opposition speaker, a trenchant critic and accuser of state officials, but he now came forward as the professed champion and leader of the democracy and, as a result, dominated Athenian politics. Although rough and unpolished, he was charismatic, being gifted with natural eloquence and a powerful voice, and he knew how to work upon the emotions of the Athenian populace. He strengthened his support amongst the poorer citizens of Athens by increasing the pay of the jurymen, which provided many of the poorer Athenians with a means of livelihood.
The fondness of the Athenians for litigation increased his power; and the practice of "sycophancy" (raking up material for false charges), enabled him to remove those who were likely to endanger his ascendancy. In 426 BC, Cleon brought an unsuccessful prosecution against Laches based on his generalship in the unsuccessful first Sicilian expedition. This is one of the very few times that an Athenian general escaped civil punishment for a defeat. Having no further use for his former aristocratic associates, he broke off all connection with them, and thus felt at liberty to attack the secret combinations for political purposes, the oligarchical clubs to which they mostly belonged. Whether he also introduced a property-tax for military purposes, and even held a high position in connection with the treasury, is uncertain.
War against Sparta, subsequent death
Cleon's ruling principles were an inveterate hatred of the nobility, and an equal hatred of Sparta. It was mainly through him that the opportunity of concluding an honourable peace (in 425) was lost, and in his determination to see Sparta humbled he misled the people as to the extent of the resources of the state, and dazzled them by promises of future benefits.
In 427 Cleon gained an evil notoriety by his proposal to put to death the whole male population of Mytilene, which had put itself at the head of a revolt. His proposal, though at first accepted, was soon rescinded, though about 1000 chief leaders and prominent men of Mytilene were executed. In 425, he reached the summit of his fame by capturing and transporting to Athens the Spartans who had been blockaded at the Battle of Sphacteria. Much of the credit was probably due to the military skill of his colleague Demosthenes (not the orator); but it must be admitted that it was due to Cleon's determination that the Ecclesia sent out the additional force which was needed.
It was almost certainly due to Cleon that the tribute of the "allies" was doubled in 425. In 422 he was sent to recapture Amphipolis, but was out-generalled by the Spartan Brasidas. However, both Brasidas and Cleon were killed at Amphipolis and their deaths removed the chief obstacle to peace. Thus, in 421 the peace of Nicias was signed.
Aristophanes and Thucydides on Cleon
The character of Cleon is represented by Aristophanes and Thucydides in a very unfavourable light, justifiable considering he instilled a feeling of mistrust within Athens through a kind of Athenian "McCarthyism" caused by the excessive number of informants he employed to keep a watchful eye on the city. But both have been suspected of being prejudiced witnesses: The poet had a grudge against Cleon, who may have accused him before the Council of having ridiculed (in his lost play Babylonians) the policy and institutions of his city in the presence of foreigners and at the time of a great national danger. Thucydides, a man of strong oligarchical inclinations, had also been prosecuted for military incapacity and exiled by a decree proposed by Cleon. It is therefore possible that Cleon has had injustice done to him in the portraits handed down by these two writers.