NEW HAVEN, Conn. (AP) This city was supposed to be a model of urban renewal in the 1960s, but by 1970 authorities were so worried about a large-scale riot that they dispatched tanks and the National Guard to New Haven.

The turbulence of the era had reached a fevered pitch as this small New England city braced for the upcoming trial of revolutionary Black Panther Party members, including founder Bobby Seale, for the murder of a suspected police informant.

Protest leaders such as Abbie Hoffman and Jerry Rubin were heading to New Haven for a massive May Day demonstration over the trial. Some agitators threatened to destroy the city, while a Yale student named Hillary Rodham was among those trying to keep the peace.

``Tanks took up positions on the roads leading into New Haven,'' journalist Paul Bass and Yale professor Douglas Rae recount in a new book, ``Murder in the Model City.'' ``Guardsmen received ammunition, gas grenades and a pep talk: Expect to see fifty thousand people out there on the green. Don't worry if you feel a need to use weapons.''

Protesters distributed gas masks and set up first aid stations. Vietcong flags filled the air and a flag pole was greased so no one would burn the flag.

``Burn, Babylon,'' demonstrators chanted. ``End U.S. imperialism around the world!''

It wasn't supposed to be this way. Civil unrest was erupting around the country, but New Haven was dubbed the ``Model City'' after launching the nation's most extensive anti-poverty campaign, spending more per capita than any other city.

But amid the splendor of Yale University, New Haven still struggled with poverty. The Black Panthers had set up a New Haven chapter and Seale, during a 1969 visit, threatened to kill police.

While Seale spoke, the suspected police informant, Alex Rackley, lay bound and imprisoned less than a mile away at Panther headquarters. Rackley was tortured with boiling water, fatally shot and his body dumped in a river about 25 miles north of New Haven.

One of the Panthers charged in Rackley's murder accused Seale of ordering the killing, leading to the trial.

Rodham, now a U.S. senator and possible presidential candidate, led a committee to monitor the trial, offer legal advice to demonstrators who got arrested and to help prevent violence at the May Day rally.

The New Haven trial sparked a protest that April at Harvard that led to a rampage in which demonstrators smashed windows, threw rocks, lit fires and clashed with police. More than 200 people were hospitalized.

Now some protest leaders vowed to burn down Yale. The university was trying to learn the lessons from Harvard by keeping its gates open so that protesters did not congregate and turn into an angry mob.

Yale President Kingman Brewster opened a dialogue with students. His approach stood in contrast to the hard line of other university presidents as well as FBI director J. Edgar Hoover and the Nixon administration.

``If New Haven blew up, hopes of a freer, more tolerant society could perish in the flames,'' the book warned.

Tensions mounted as the rally began. A bottle was thrown at the guardsmen and police, followed by bricks and cherry bombs. Police shot tear gas canisters into the crowd.

Demonstrators regrouped a few blocks away. Seale released a statement appealing for calm.

But some demonstrators refused to back down from Nixon's National Guard, who stood with bayonets pointed. More rocks and bottles flew, prompting the guard to set off 30 tear gas grenades.

Just before midnight, two bombs exploded at a concert as the last rock band was finishing its performance. The blasts blew out glass and cracked a ceiling, but no one was seriously injured.

On the second day of the expected three-day rally, the crowds had dwindled. A pilot made a peace sign in the sky. Demonstrators left before the third day for new protests around the country.

``Call it luck. Call it brilliant planning,'' Bass and Rae wrote. ``Call it a conspiracy between the Man and the Panther. Whatever the reason, death and destruction passed by New Haven.''

Two days later, National Guardsmen at Kent State University in Ohio, armed with the same weapons and orders as their fellow soldiers in New Haven, shot and killed four students during an anti-war protest.

The New Haven trial resulted in a hung jury and the charges were dismissed against Seale, who could have faced the death penalty, and other defendants. Some Panthers were convicted before and after the trial.

David Rosen, an attorney who represented Seale, said the Panthers were committed to a peaceful protest in that instance because they were confident the trial would exonerate Seale.

``It was an ironic twist on the Panther slogan, which was the menacing phrase, 'Free Bobby by any means necessary,''' Rosen said. ``The legal system channeled the enormous conflicting energies of the different groups into a small room in New Haven where everything played out in an orderly way.''

Hugh Keefe, an attorney who represented some of the Panthers and was in the National Guard dispatched to the city, said the guard had limited training and patrolled without bullets.

``It was a miracle there wasn't bloodshed that weekend,'' Keefe said.