Background
After the founding of the PRC in 1949, the CCP was focused on emphasizing the basis of the Social Democracy ideal towards the people of the country. What will be known as the Hundred Flowers Movenment was first a small campaign aimed solely at local bureacracies for non-communist-affiliated officials to speak out about the policies and the existing problems within the central bureacracy. Premier Zhou Enlai was initially the head of this first campaign.
Despite continuous efforts put henceforth by Zhou Enlai and other prominent central bureacratic officials, this minimalized campaign was a failure. No one spoke out openly at all.
During a Communist Politburo Conference in 1956, Zhou Enlai emphasized the need for a bigger campaign, aimed this time at the whole sea of intellectuals within the country, for these individuals to criticize the central government. Mao initially had supported the idea. "The government needs criticism from its people," Zhou said in one of his 1956 speeches, "Without this criticism the government will not be able to function as the 'People's Democratic Dictatorship'. Thus the basis of a healthy government lost... We must learn from old mistakes, take all forms of healthy criticism, and do what we could to answer these criticisms."
Hundred Flowers
In the summer of 1956, Mao had found the idea an interesting one, and had started to take central control over that of Zhou Enlai's in the actual campaign. The idea, modified more or less by Mao, was to have intellectuals discuss the country's problems in order to promote new forms of arts and new cultural institutions. In a later speech made by Mao titled On the Correct Handling of the Contradictions Among the People, Mao had openly and wholeheartedly supported the campaign, saying "Our society cannot back down, it could only progress... criticism of the bureacracy is pushing the government towards the better."
Thus began the ill-fated Hundred Flower's Movement.
The name of the movement had originated from a poem: 百花齊放，百家爭鳴 "Let a hundred flowers bloom: let a hundred schools of thought contend." Mao had used this to signal what he had wanted from the intellectuals of the country.
The campaign publicly started in late 1956. In the starting stages of the Movement the Central Government was still not receiving any forms of criticism, although there was a significant rise in letters of conservative advice. Premier Zhou received some of these letters, and once again realized that this widely publicized campaign was not progressing. Zhou later spoke to Mao about the situation, stating that even more euphoria is needed from the central bureaucracy to lead the intellectuals into further criticism.
By the Spring of 1957, Mao had announced that criticism was needed and had started to criticise those who failed to turn in healthy criticism to the Central Government. Many intellectuals, already estimating that this was a plot of some sort, finally gave in to their firy thoughts. In the period from June 1 to July 17, 1957, millions of letters where pouring in to the Premier's Office and other authorities.
Many of these letters, as stated by Mao in early 1957, had violated the Healthy Criticism level and had reached a harmful and uncontrollable level, which indeed was true. These letters had advised the government to "govern democratically" and "open up", Premier Zhou Enlai at first had explored and listened to many of these criticisms, but Mao refused to do this himself. Mao had began or simply continued an old apprehension: those who criticise harmfully mean an end to his leadership. By early February 1957 the euphoria was simply too hard to control, many absurd letters were turned in. Statements by intellectuals (or others who sent in letters) got to the point where they suggested "the CCP should give up power", "intellectuals are virtually being tortured to live in a communist society", "there is absolutely no human rights and freedom if the CCP is to continue on ruling the country", "the country should separate with each Political Party controlling a zone of its own" and "Each political party in China should rule in transitional governments, each with a 4 year term".
The Hundred Flowers Movement had turned into nothing it projected. No new forms of cultural institutions or arts is being suggested by these intellectuals (or for that matter all of those letters containing new arts or insititutions were all ignored, being that attention was focused elsewhere anyhow), instead just "unhealthy" political criticism.
Mao had simply grew sick of continual bashing of the CCP, the letters and "advice" had angered Mao deeply. In July 1957, Mao ordered the halt of this campaign, and Zhou had no powers to stop him. Mao's earlier speech, On the Correct Handling of the Contradictions Among the People, which was never published, was meaningfully changed and appeared later on as an anti-rightist piece itself. Some concluded that Mao knew the outcome before the campaign had even started.
After the Campaign
After the ill-fated campaign was officially declared over, Mao's hate for the intellectual population had accumulated. Continuing with an Anti-Rightist Movement he had started only years past, he reasoned that the intellectuals were the basis of all existing problems. Mao had ordered arrests of counter-revolutionaries on the basis of their letters and punished many harshly, as far as using torture and capital punishment without any form of trial.
Hence also began some of Mao's radical ideas (see Maoism) that would last in the policies of the CCP until the end of the Cultural Revolution in 1976.