Six years after tanks and machine guns silenced their democracy movement, Chinese student leaders who rallied a nation during six weeks of protest at Tiananmen Square in 1989 are at odds with one another over the history of the event.

The production of two new documentary films, both based on extensive reconstructions of the days leading up to the military assault on central Beijing on June 3-4, has resurrected the debate over whether the students should have surrendered the 99-acre square before the crackdown and thus avoided the bloodshed that claimed hundreds of lives.

The debate does not call into question the overall motives of the spontaneous pro-democracy protest that began on April 15, 1989, nor does it seek to excuse the brutality of the Chinese Government for the deaths that occurred when 200,000 army troops were ordered to reclaim central Beijing from the students.

But a central question for many in the student movement, and for some historians, is whether moderation gave way to extremism during those six weeks and whether the more radical student leaders spurned opportunities to declare victory by ending the demonstrations and preserving, perhaps, the reformist trend that was still a prominent feature of the Chinese leadership.

To document the streak of radicalism in the student movement, the Boston-based producers of a three-hour documentary that is scheduled to be shown on the Public Broadcasting System this year are bringing new focus to a lengthy videotaped interview given by one student leader, Chai Ling, five days before the military crackdown.

In it, Ms. Chai said the hidden strategy of the leadership group she dominated was to provoke the Government to violence against the unarmed students. With statements like "What we are actually hoping for is bloodshed" and "Only when the square is awash with blood will the people of China open their eyes," Ms. Chai denounced those students who sought to bring an end to the occupation of the square.

These remarks, which have never been fully presented, provide new insight into the tension-filled environment that was generated by mass demonstrations in 1989. Ms. Chai now argues that what she said at the time should be viewed in light of the highly charged standoff with the Government, and not as examples of extremism.

The overall re-examination of Tiananmen comes as China's Communist Party leadership is preparing for the death of Deng Xiaoping, whose departure as paramount leader is expected to pave the way for a full reassessment of the party's condemnation of the demonstration by hundreds of thousands of people as a "counterrevolutionary rebellion."

Mr. Deng's youngest daughter, Xiao Rong, the first member of the family to address the subject publicly, indicated in an interview this year that a national reconciliation over Tiananmen would be up to "the people who come after" her father.

For the thousands of students who fled abroad, or were imprisoned, and for millions of Chinese who have lived through years of hard-line repression since 1989, the time may finally be approaching to reassess, if not lift, the Tiananmen verdict.

"If there is a reconsideration of the movement, part of the work of everyone who participated will be to face their own moral responsibility, even though it was the Government that opened fire," said Liu Xiaobo, one of the Chinese intellectuals who persuaded the last 3,000 students to leave the square at 5 A.M. on June 4 -- after a nightlong assault on the streets of Beijing.

Drafting a "correct history" of the 1989 movement is the "solemn responsibility" of its leaders," said Mr. Liu, now 40, who spent 19 months in prison after the crackdown.

The debate over the outcome at Tiananmen began among the student leaders almost immediately after the crackdown and has continued among historians since, although mostly out of public view.

But this year's re-examination, in part prompted by these new documentary accounts, is bringing discomforting issues to the fore.

In "Moving the Mountain," a documentary that is opening this month in New York, another protest leader, Wang Chaohua, gives tearful testimony to the students' "mistakes" that provoked the Government assault and she reveals her anger at Ms. Chai, who became the uncompromising icon of the movement in its final days.

Today, Ms. Wang, now 42, wants nothing to do with the promotion of the documentary, arguing that it lionizes the roles of Ms. Chai, now 29, and her deputy on the square, Li Lu, now 27.

For her part, Ms. Chai defends her actions.

"I don't agree with the word 'radical,' or 'extremist,' " she said in an interview from Boston, where she now lives.

Ms. Chai asserted that the goal of the movement was to establish a dialogue with the Government and that this never changed.

The documentary's director, Michael Apted, said by telephone from Los Angeles that he and the producer, Trudie Styler, had acquired the rights to Mr. Li's autobiography, but that they decided to broaden the work to include other voices when they realized "how disparate the views and how unreconciled" the student leaders were.

"I never said it was objective or reasoned or balanced," Mr. Apted said. "Trudie wanted to make an emotional film, to see the price people paid."

The second documentary, "The Gate of Heavenly Peace," is being produced by the Long Bow Group of Boston and may be the most comprehensive documentary work on Tiananmen to date. The film's producers, Richard Gordon and Carma Hinton, have spent five years assembling an international archive of videotape and tape-recorded interviews to examine the entire student movement.

Their thesis, that moderation was swept aside during the final days of the demonstrations, has previously been raised by some who watched the events unfold.

"If the students had left earlier, there wouldn't have been a massacre," said Robin Munro, the Hong Kong director of the New York-based Human Rights Watch, who was a witness to the events of 1989. "I wouldn't take the next step and say the students are responsible for the massacre. But if they had left earlier, there would not have been a June 4 and the legacy of the movement, the icon of the massacre, would not be the same."

In 1993, Mr. Munro co-wrote a detailed account of the efforts by a number of Chinese intellectuals and student leaders to head off the military assault. These efforts failed not for lack of broad support, he argued, but because the most uncompromising of the student leaders, principally Ms. Chai and Mr. Li, would not agree to abandon the square.

Orville Schell, an author who has written extensively on China, said: "They were young, extreme. They played to the crowd and they really didn't know where they were going."

But, Mr. Schell added, "the historical record now speaks for itself with greater clarity than ever before on the dynamic of the whole movement and on how extremism did prevail in the end."

"The Gate of Heavenly Peace" will challenge the conventional wisdom that the student leadership was unified and that it was unerringly dedicated to nonviolence and dialogue with the Chinese Government, said Mr. Schell, who is an adviser to film.

Five days before the military assault, according to the documentary, Ms. Chai told Philip Cunningham, an American journalist: "How can I tell them that what we are actually hoping for is bloodshed, the moment when the Government is ready to brazenly butcher the people? I feel that only when the square is awash with blood will the people of China open their eyes."

Referring to those who were trying to prevent violence, she said, "They are trying to cause our movement to disintegrate and get us out of the square before the Government is provoked to violence."

Ms. Chai also said she herself was not prepared to stay in the square.

"I'm not going to be destroyed by this Government," she said in the interview. "I want to live. Anyway, that's how I feel about it. I don't care if people say I'm selfish."

Ms. Chai said she now generally remembered making these statements but argued that they should be placed in the context of six weeks of confrontation with the Government.

After Ms. Chai and other student leaders voted on May 27 to declare victory on May 30 and march off the square, she changed her mind upon returning and being confronted by Mr. Li, who angrily denounced the decision.

Speaking by telephone from New York, where he is studying law and business administration, Mr. Li said that "if we left the square what would happen is very simple." The Government, he said, would still have carried out a vast campaign of arrests, secret killings and persecution.

As troops moved forward on the morning of June 4, Mr. Liu and others negotiated with an army colonel to allow the students a safe withdrawal, which happened at 5 A.M., about eight hours after the shooting began in various parts of central Beijing.

"To this day, Li Lu has not reflected critically on his actions in the movement," said Zhou Duo, 48, a participant in the movement who remained in China. "In fact, in many people's view, Chai Ling and Li Lu were the ones who ruined things. They were the ones who brought events to the point that no one wanted to see."

Mr. Schell said that the two films portray competing images of the student movement.

"There will be a war over which one is the right historical interpretation," he said, "and it's starting. This is a history that is howling to be told."