After serving in World War II and losing many of his Harvard classmates on the battlefield, Roger Fisher devoted himself to studying ways of resolving conflict on international and personal levels. Catastrophic violence, he concluded, was a lousy way to solve problems.
He devised a toolbox for conflict negotiation and as a Harvard law professor coauthored the 1981 best-selling book, “Getting to Yes: Negotiating Agreement without Giving In.”
“Roger sought unabashedly to change the world, and he did so profoundly,’’ said Bruce Patton, who met him in 1978 as a Harvard student and co-wrote “Getting to Yes” with Mr. Fisher and William Ury. More than 8 million copies have been sold.
Mr. Fisher died Saturday at a nursing home in Hanover, N.H., from complications of dementia. He was 90.
At the heart of his methods was teaching players to understand the interests of their opponent and reframe their conflict to reach a resolution that would satisfy all.
At Mr. Fisher’s 80th birthday party, the late John Kenneth Galbraith, his friend and Harvard colleague, told well-wishers, “Whenever I thought, ‘Someone should do something about this,’ it eased my conscience to learn that Roger was already working on it.’’
Mr. Fisher received numerous awards for his work in alternative dispute resolution and conflict management. At the time of his death, he was the Williston professor of law emeritus at Harvard Law School.
Among his accomplishments, Mr. Fisher helped facilitate peace in El Salvador in the 1990s, according to co-workers from his consulting firms. Leaders of warring factions attended a series of his workshops and later signed peace agreements ending a long civil war.
Mr. Fisher also spent several months in South Africa in the early 1990s running workshops for the country’s leaders, who were creating a new constitution.
“He was a master teacher,” said his former Harvard student Irma Tyler-Wood, who left practicing law in 1988 and accompanied Mr. Fisher to South Africa.
“I don’t think he ever got the credit or recognition he should have gotten,” said Tyler-Wood, a negotiation expert and founder of the Cambridge firm ThoughtBridge. “To me he’s like Johnny Appleseed on a whole different level. He planted these ideas all around the world with people who are using them to do remarkable things.”
Mr. Fisher waded into a long-running border dispute in 1995 that had turned into war between Ecuador and Peru. He led discussions in Cambridge with former and current officials. The brainstorming sessions set the stage for an accord eventually reached in 1998.
“One of the maxims he preaches is you should separate the people from the problem. You can be very kind with the people and very tough on the problem. He was able to do that in real life,” said his friend Jamil Mahuad, who was president of Ecuador from 1998 to 2000.
He described Mr. Fisher as a kind and generous man who embodied Ghandi’s call to “be the change you want to see in the world.”
Born in Winnetka, Ill., Mr. Fisher was one of six siblings. His father was secretary of the interior under President Taft.
He was married 62 years to the former Caroline McMurtrie Speer. She died in 2010.
They had two sons; Elliott is director for population health and policy at the Dartmouth Institute, and Peter R. was undersecretary of the Treasury from 2001 to 2003 and is now senior managing director at BlackRock, a multinational investment management corporation.
“There’s not a day that I don’t use some of his ideas,” said Elliott, a doctor in Vermont, who recalled many conversations with his father about his own efforts in advocating affordable health care.
Mr. Fisher served in the Army Air Forces from 1942 to 1946 in weather reconnaissance in the North Atlantic and the Pacific. He was a first lieutenant.
He earned his undergraduate degree from Harvard in 1943 and his law degree in 1948.
After graduation, he was offered a clerkship under Judge Learned Hand but decided to take a post serving on US Ambassador Averell Harriman’s Marshall Plan staff in Paris, his family said.
He later worked at a Washington law firm and was assistant to the solicitor general from 1956 to 1958. He argued several cases before the Supreme Court.
He became a Harvard law professor in 1960. In 1969, Mr. Fisher penned “International Diplomacy for Beginners” complete with sardonic illustrations by Robert C. Osborn.
“His pragmatism and his value-free cool may provoke attack from those who would like to revamp the American government, rather than merely to make it more effective in pursuit of its business,” Kirkus Reviews said of the book.
Mr. Fisher spent many happy summer days on Martha’s Vineyard, his family recalled, but was always focused on ways to improve the world. He wrote many op-ed columns published in The New York Times and The Boston Globe.
During the Iranian hostage crisis in 1979, Dr. Fisher advocated efforts to change the conflict from a contest of will to one of principle.
“We are learning that true power comes not from B-52s but from understanding the legitimate interests of others and then insisting upon adherence to principles that serve their interests as well as ours,” Mr. Fisher wrote.
In addition to his sons, Mr. Fisher leaves two brothers, Frank of Austin and John of Spokane, Wash.; and five grandchildren. A memorial service is planned for 11 a.m. Oct. 27 at Appleton Chapel at Harvard. Burial will be private.
At Mr. Fisher’s 90th birthday party this spring, Shelia Heen, a former student who now teaches conflict resolution, told of meeting a soldier in the US Special Forces’ civil affairs division who carried “Getting to Yes” on six tours of duty in Iraq and Afghanistan.
“He thought Roger would get a kick out of the fact that he’s on the ground, influencing the conversation, in a war 70 years after his own,” she said.