Two decades ago, Richard Goldstone, a Jewish South African judge, played a vital role in reconciling his country’s white minority government and rising black majority movement by leading a fact-finding mission into black violence that offered a Solomonic conclusion.

The violence, he found, was endemic, but a covert government campaign was sponsoring black killings to undermine the opposition. Heads rolled, hands were shaken and Mr. Goldstone was hailed as the most trusted man in the country, going on to a distinguished international career.

In 2009, he tried to do the same thing in the other country close to his heart: Israel. Mr. Goldstone, a Zionist who believes that political reconciliation will result when both sides face the unbiased rigors of international law, agreed to lead a United Nations inquiry into the war between Israel and Hamas, telling friends that the mission could make a real contribution to Middle East peace.

The resulting report that bears his name accused each side of wrongdoing — deliberately making civilians targets. But the report not only failed to bring peace to the region and universal honor to its author. It also hardened positions and brought a storm of attacks on Mr. Goldstone, especially from within his community.

In trying to understand why he published an essay on April 1 in The Washington Post retracting his harshest accusation against Israel and toughening his stand toward Hamas and the United Nations — an essay that has been rejected by the fellow members of his investigation panel — the South African precedent is important. For Mr. Goldstone, it was the model of how the Gaza report would work. Instead, it helped drive Israeli politics farther to the right, gave fuel to Israel’s enemies and brought no notable censure on Hamas.

“I know he was extremely hurt by the reaction to the report,” said Aryeh Neier, president of the Open Society Foundations, who has known Mr. Goldstone for years and remains close to him. “I think he was extremely uncomfortable in providing some fodder to people who were looking for anything they could use against Israel.”

In describing his new position, Mr. Goldstone wrote, “If I had known then what I know now, the Goldstone report would have been a different document.” He has declined requests to elaborate. Interviews with two dozen people who know him suggest a combination of reasons: the hostility from his community, disappointment about Hamas’s continuing attacks on civilians, and new understanding of Israel’s conduct in a few of the most deadly incidents of the war.

The year and a half since the Gaza report was published have been hard on Mr. Goldstone. Hailed by the Arab world and the anti-Israel left, he has been censured by those with whom he had always identified. One of his two daughters, who spent more than a decade in Israel and now lives in Canada with the man she married here, has been furious with him, according to a family friend; he was nearly unable to attend the bar mitzvah of his other daughter’s son in South Africa because of plans by some members of the Jewish community there to demonstrate against his presence.

“He told me last year that he was dreaming of the day when he would be able to sleep again at night,” a longtime friend said, asking for anonymity for fear of angering Mr. Goldstone by speaking about private conversations. In the past two weeks, he has been embraced by some who had shunned him.

When Mr. Goldstone was asked to investigate the three-week Gaza war, which started in late 2008, he was told by many friends of Israel that he was stepping into a trap. There had never been a United Nations Human Rights Council investigation into possible war crimes in Chechnya or Sri Lanka, but there had been multiple ones into Israel’s actions.

Mr. Goldstone persuaded the council’s president to agree that the mandate would not be limited to Israel. He believed that both Israel and Hamas could be prodded to change their ways.

As he said in an interview with the newspaper The Forward: “I was driven particularly because I thought the outcome might, in a small way, assist the peace process. I really thought I was one person who could achieve an evenhanded mission.”

Some attribute that sentiment to a well-developed sense of ambition. With a nod to Boutros Boutros-Ghali, then the United Nations secretary general, some called him Richard Richard-Goldstone, according to Benjamin Pogrund, a South African journalist.

But from the beginning of the Gaza endeavor, Mr. Goldstone’s expectations were dashed. As a longtime supporter of Israel, he thought he could persuade its government to cooperate. He had been a governor of the Hebrew University in Jerusalem, chairman of the university’s South African Friends and president of World ORT, a Jewish vocational training organization.

Yet Israel declined, citing the bias of the council and the fact that the written mandate was never officially altered. This meant that his team was not permitted into Israel to witness the destruction caused by Hamas’s rockets.

And what it found in Gaza shocked Mr. Goldstone: thousands of destroyed homes, hundreds of leveled workshops and factories, the Parliament building in rubble and up to 1,400 dead, many of them civilians. Israel lost 13 people.

“It was a nightmare experience to visit Gaza and witness at first hand all of this destruction and to witness at first hand the effects this has on the men, women and children of that overcrowded enclave,” Mr. Goldstone said in a speech last month in Sacramento.

He added that he was sure it would also have been “an emotional and distressing experience” to visit the many victims of the thousands of rockets over the years fired from Gaza into southern Israel. “I deeply regret that the Israeli government denied us that opportunity,” he said.

The lack of access to Israel and its military, Mr. Goldstone implied in numerous statements, led to a somewhat skewed report that needed to be adjusted.

He noted in Sacramento, for example, as in his later essay, that the deaths of about 29 members of one Gazan family grouped together by Israeli soldiers in a building that was subsequently bombed probably resulted from a misreading of a drone photograph. Men carrying firewood might have looked as if they were holding rocket launchers.

At a debate last month at Stanford Law School, he did not excuse that Israeli killing but said that originally, “in the absence of any evidence at all, the only conclusion we could come to was that it was intentional.” Now it appeared to have been negligence due to lack of communication and verification, he said, adding: “I think that many aspects, many things have happened since the report has been published. I just think it’s a pity that they’ve been ignored.”

In truth, even many who hailed the Goldstone report in the human rights world, in Israel and the United States, were uncomfortable with its assertion that Israel intended to kill civilians.

Maurice Ostroff, a retired South African engineer who lives outside Tel Aviv and has maintained a steady correspondence with Mr. Goldstone, said he saw the Washington Post essay as the result of a slow, gradual rethinking.

“He was upset by the misuse of those who accused Israel of being an apartheid state,” Mr. Ostroff said. “But mostly, as new information came out, he shifted his thinking.”

In Sacramento, Mr. Goldstone told of a speech he gave at Yale in late 2009.

During the presentation, three men in the hall unfurled a banner listing what they viewed as great libels directed at the Jewish people: “Protocols of the Elders of Zion — Dreyfus — Goldstone.”

The first referred to a Russian forgery alleging Jewish plans to rule the world, and the second to the framing of a Jewish army officer in France who was accused in 1894 of passing military secrets to the Germans.

Afterward, one of the three, Rabbi Shmully Hecht, went up to Mr. Goldstone and asked, “How would you feel if all the allegations made against Israel in your report were proven to be incorrect?”

Mr. Goldstone replied, “I would rejoice.”

To friends and acquaintances, Mr. Goldstone has noted several points of new information that swayed him — besides the undue focus on Israel at the United Nations and its refusal to condemn continuing rocket fire by Hamas, and the fuzzy drone picture, he has rethought the question of combatants versus civilians killed in Gaza.

Israel has maintained that about 700 of the dead, which it put at 1,166, were combatants. Palestinian estimates and those of some human rights groups put the total at more like 1,400 and the number of combatants at only a few hundred.

One area of disagreement was whether 250 police cadets killed on the first day should be considered fighters. Israel said yes; most others said no.

In November, the Hamas interior minister, Fathi Hamad, told the newspaper Al Hayat that many of the dead were fighters: “It is a fact that on the first day of the war, Israel struck police headquarters and killed 250 members of Hamas and the various factions, in addition to the 200 to 300 operatives from the Qassam Brigades. In addition, 150 security personnel were killed.”

The implication was that the 250 cadets were fighters and that the total number of militants killed amounted to about 700. Many sent Mr. Goldstone the update.

Mr. Goldstone has not repudiated the report, with its allegation of systematic Israeli destruction of civilian infrastructure, or called for it to be nullified, although he said he remains open to new facts.

In the essay, he noted that Israel has, as a result of his report, adopted combat procedures to protect civilians better, including limiting the use of white phosphorus, which causes severe burns, in populated areas.

The Anti-Defamation League noted that after Mr. Goldstone’s essay, anti-Semitic cartoons appeared in the Arab press depicting the Jewish lobby silencing him.

All of which has left Mr. Goldstone, at age 72, with something of a mixed scorecard on advancing Middle East peace. He seems aware of that. At his Sacramento speech, he was asked whether he had come to regret agreeing to lead the investigation.

“Yes and no,” he replied. He did not elaborate.