As a radical pacifist, the American-born David Dellinger, who has died aged 88, spent his life involved in non-violent action against war and oppression. But his most prominent role was as elder statesman of the Chicago Eight, the disparate group of radicals who were charged with conspiring to incite riots around the 1968 US Democratic party convention which endorsed Hubert Humphrey's nomination as presidential candidate after President Lyndon Johnson withdrew from the race at the height of the Vietnam war.

Dellinger's principled stand and commitment to non-violence belied Washington's accusations against him, and, for many involved in the anti-Vietnam movement, served as an inspiration.

By the time he graduated from Yale University in 1936, with honours in economics and as captain of the cross-country team, Dellinger was already being radicalised. He had been arrested while marching to support unionisation at Yale; he spent a summer working in a factory in Maine, and another travelling with hoboes. His friends included the young Walt Rostow (obituary, February 17 2003), who then argued the virtues of communism, which Dellinger found lacked a "spiritual dimension". Rostow went on to become an architect of Vietnam policy under US presidents Kennedy and Johnson.

Dellinger discovered his pacifism when, during a brawl at a Yale football game, he punched a New Haven "townie". As his victim fell, stunned, he later wrote, "the lesson I learned was as simple, direct and unarguable as the lesson a child learns the first time it puts its hand on a red-hot stove. Don't ever do it again!"

I'm in shock. I just received an email from a very good friend here in Vermont telling me that David Dellinger died the afternoon of May 25th. Dave was a lifelong antiwar activist who refused to fight in World War Two and actively opposed every US war since then. He was 88 years old and had been suffering from worsening health. Indeed, he had just been moved to a nursing home not more than two or three months ago.

Although I only met Dave five years ago when a group of us sat in on Representative Bernie Sanders' office in opposition to his support of the bombing of Yugoslavia, he has been an influence on my life and thought ever since I first heard about him in junior high. As a young peacenik who found the militancy and flamboyance of activists and groups like the Black Panthers and Yippies quite appealing, it was David Dellinger's thoughtful, yet militant antiwar stance that provided me (and millions of others, it seems) with a fundamental belief that what I was doing was worthwhile. After all, this man had devoted his entire adult life to opposing imperialism and the wars that system demands without ever even throwing a brick at a cop. Like the Berrigan brothers and Martin Luther King, Jr., his commitment to nonviolence was total. At the same time, he understood that pacifism was not passivism.

Peace activist David Dellinger, one of the Chicago Seven arrested and tried for their part in the violent anti-war protests outside the 1968 Democratic National Convention, has died at 88.

Dellinger died Tuesday, said Peggy Rocque, administrator of Heaton Woods, the Montpelier retirement home where the activist had been living.

Dellinger was a pacifist who devoted much of his life to protesting. A member of the Old Left whose first arrest came in the 1930s during a union-organizing protest at Yale, he was a generation older than his Yippie co-defendants in the Chicago Seven case.

"Mainly I think he'll be remembered as a pacifist who meant business," said Tom Hayden, a fellow '60s radical and member of the Chicago Seven who went on to become a California legislator. "His pacifism was very forceful. He didn't mind interjecting himself between armed federal marshals and someone they were pushing around."

At the Chicago Seven trial in 1969 and 1970, Dellinger and four co-defendants - Hayden, Jerry Rubin, Abbie Hoffman and Rennie Davis - were convicted of conspiracy to incite a riot at the 1968 convention. Those convictions were overturned by a federal appeals court, which cited errors by U.S. District Judge Julius Hoffman.

When Hoffman invited Dellinger to address the court during sentencing, he continued to speak after the judge ordered him to stop.

"You want us to be like good Germans, supporting the evils of our decade, and then when we refused to be good Germans and came to Chicago and demonstrated, now you want us to be like good Jews, going quietly and politely to the concentration camps while you and this court suppress freedom and the truth," Dellinger told the judge. "And the fact is, I am not prepared to do that."

Greg Guma, editor of the political magazine Toward Freedom, called Dellinger "one of the major figures in terms of peace and social justice of the last half century."

David Dellinger, whose commitment to nonviolent direct action against the federal government placed him at the forefront of American radical pacifism in the 20th century and led, most famously, to a courtroom in Chicago where he became a leading defendant in the raucous political conspiracy trial of the Chicago Seven, died Tuesday in a retirement home in Montpelier, Vermont. He was 88.

An avuncular figure among younger and more flamboyant mavericks, Mr. Dellinger emerged in the 1960's as the leading organizer of huge antiwar demonstrations, including the encirclement of the Pentagon that was immortalized in Norman Mailer's account "Armies of the Night." At the same time, making use of his close contacts with the North Vietnamese, he was able to organize the release of several American airmen held as prisoners and to escort them back from Hanoi.

In the often turbulent world of the American left, Mr. Dellinger occupied a position of almost stolid consistency. He belonged to no party, and insisted that American capitalism had provoked racism, imperial adventures and wars and should be resisted.

A child of patrician privilege, he had since his days at Yale learned and practiced strategies of civil disobedience in a variety of causes, steadfastly showing what he called his concern for "the small, the variant, the unrepresented, the weak," categories he cited from the writings of William James.