Li Peng panicked and fled from Tiananmen Square, Jiang Zemin was overwhelmed by the demonstrations in Shanghai and Hu Yaobang was careless and sometimes hasty, according to ousted party boss Zhao Ziyang.
Zhao's memoirs make many claims about top state leaders and shed light on the power struggles at the royal court of the Communist Party.
His depiction of then premier Mr Li, a key figure in the June 4 crackdown, is of a man who was a coward, personally repulsive and incompetent. Zhao writes that Mr Li, having tried and failed several times to stop him meeting the students, went to Tiananmen Square with him in the early morning hours of May 19, but fled soon after their arrival.
'I insisted on going, saying that if no others went, I would go alone,' Zhao writes. 'Once he [Li Peng] saw that I was intent on going and could not be deterred, he changed his mind. But he was terrified and fled very soon after we arrived at the square.'
Even before Zhao's famous meeting with students in the square - televised in Hong Kong and abroad - Mr Li was already preparing for 'leadership changes', Zhao writes.
After a meeting with Soviet leader Mikhail Gorbachev, Zhao called a meeting of party leaders on the night of May 16 to discuss issuing a public statement in the name of the politburo standing committee to ask students to stop the demonstrations.
But Mr Li was not willing to include the word 'approve' in the statement which attempted to assuage students' anger by describing the 'passionate patriotism' of the students as 'admirable'.
Zhao said: 'I was quite repelled by Li Peng's attitude, and said: 'If we don't mention 'approval', it's as if we'd said nothing at all ...'
'After a meeting at Deng Xiaoping's home on May 17, Li Peng and his associates acted abnormally in many ways,' Zhao writes. 'Whether I was going to the hospital or to the square to visit students, he repeatedly attempted to block me.
'When I arrived and I exited the van, he rushed out in front of me, which was contrary to custom. Someone later told me that he instructed people to hint to the cameramen not to include images of me, because it would become 'inconvenient' in the event of future leadership changes.'
Zhao writes that the decision on who should be premier (the role went to Mr Li before Tiananmen) had taken a long time because Mr Li had no experience in managing the economy.
Deng was hesitant about appointing him and had to ask Zhao to continue overseeing the economy although Zhao had already been promoted to party boss.
Deng had acknowledged that Mr Li had 'a bad reputation' and that he had once visited the Soviet Union without informing anyone during a visit to Europe.
The memoirs also challenge conventional wisdom that former president Jiang was decisive when handling the 1989 student demonstrations in Shanghai and that his actions caught the attention of Deng, who later elevated by him to replace Zhao.
Instead, Zhao says that Mr Jiang was overwhelmed by the demonstrations in Shanghai and sought his help. Unhappy with Zhao's advice, he later cited the incident in condemning him.
'On May 10, Jiang Zemin came to Beijing and talked to me about plans to reduce tensions. I told him the matter should be resolved in Shanghai without the interference of the Central Committee ... Jiang Zemin was unhappy about this,' Zhao writes.
Zhao writes that while Hu Yaobang, his predecessor as general secretary, was reform-minded and tolerant, he was careless and his slips of the tongue on public occasions and during interviews, including during an interview with Hong Kong journalist Lu Keng, upset Deng and was the true reason for his downfall.
In his own words
Quotable quotes from Zhao Ziyang?s memoirs
First, it was determined that the student movement was a planned conspiracy of anti-party, anti-socialist elements with leadership ... What evidence exists to support this?
Second, it was said that this event was aimed at overthrowing the People?s Republic and the Communist Party. Where is the evidence?
Western parliamentary system
It is the western parliamentary democratic system that has demonstrated the most vitality. This system is currently the best one available. It is able to manifest the spirit of democracy and meet the demands of a modern society
If we don?t move toward this goal, it will be impossible to resolve the abnormal conditions in China?s market economy: issues such as an unhealthy market, profiting from power, rampant social corruption and a widening gap between rich and poor. Nor will the rule of law ever materialise