JERUSALEM — Leaders from almost 50 countries condemned anti-Semitism old and new here Thursday, using the 75th anniversary of the liberation of the Auschwitz concentration camp to mount a united stand against the resurgence of anti-Jewish sentiment around the world.

Vice President Pence and House Speaker Nancy Pelosi were among the dignitaries gathered at Yad Vashem, Israel’s somber memorial to the Holocaust’s 6 million Jewish victims, for the World Holocaust Forum, one of the largest international events ever hosted by the country.

Leaders of World War II’s Allied powers addressed the body, which included about 100 of the fast-dwindling number of Holocaust survivors, warning that the hatred that fostered the industrial murder of the Jewish people is festering again and manifesting itself in incidents both trivial and terrorizing, from swastikas painted on gravestones to mass shootings at synagogues.

Besides Pence, speakers included Britain’s Prince Charles, French President Emmanuel Macron, Russian President Vladimir Putin, German President Frank-Walter Steinmeier, as well as Israeli President Reuven Rivlin and Prime Minister Benjamin Netanyahu.

Now is the time, organizers said, to turn such commemorations into a real-time call to action.

“Ladies and gentlemen, I commit that the words ‘Never Again’ will not be an empty slogan, but will be an ongoing decree, an imperative that must be followed,” Netanyahu said. He called the gathering “a sign of hope.”

Moshe Kantor, the Russian philanthropist and president of the World Holocaust Forum Foundation, which organized the gathering, likened the moment to attempts by world leaders eight decades ago to address rising violence against Jews in Europe.

The 1938 Evian Conference “ended up with no agreement and no result,” Kantor said in an interview, a failure that paved the way for the atrocities that followed. “This is why the level of anti-Semitism in the world should serve as a moral barometer.”

President Trump, who has been criticized for not condemning anti-Semitic rhetoric by some of his supporters, including at a 2017 white supremacist rally in Charlottesville, did not attend the forum. But he did proffer a comment to be included in a commemorative album about the event.

“We have a fundamental and collective duty to ensure that each new generation knows the truth,” Trump wrote. “The lessons of the Holocaust must forever be engrained in the consciousness so that we can fulfill our solemn and sacred promise that such evil and hatred will never again come to power.”

Pence, in his remarks, joined the call to link historical atrocities — such as those exposed when Soviet troops entered the gates of Auschwitz — with more recent offenses.

“We must confront and expose the rising tide of vile anti-Semitism fueling hate and violence across the broader world.”

He and Netanyahu singled out Iran as a particular threat. Pence said Tehran is the “one government in the world that denies the Holocaust as a matter of state policy and threatens to wipe Israel off the map.”

Charles, whose paternal grandmother, Princess Alice, is honored by Israel for hiding a Jewish family in Athens during the Holocaust, drew a connection between survivors of the concentration camps and today’s victims of hatred.

“The Holocaust must never be allowed to become simply a fact of history,” he said. “We must be vigilant in discerning these ever-changing threats.”

In a closing address, Steinmeier acknowledged German responsibility for the Holocaust, which he called “the worst crime in the history of humanity.” But he cautioned that atonement alone cannot prevent hatred from surging again.

“I wish I could say that we Germans have learned from history once and for all,” Steinmeier said. “But I cannot say that when hatred is spreading. I cannot say that when Jewish children are spat on in the schoolyard. I cannot say that when crude anti-Semitism is cloaked in supposed criticism of Israeli policy.”

The World Holocaust Forum all but took over the Holy City, forcing street and school closures and drawing more than 11,000 security officers from across the country and about 500 journalists from around the world (including 107 who came with Putin). Hotels scrambled to accommodate presidents and princes as motorcades filled roads.

Many of the participants were traveling from another global gathering, the World Economic Forum in Davos, Switzerland. Among those who had planned to make the trip was Jared Kushner, Trump’s son-in-law and keeper of the long-delayed White House peace proposal between Israel and the Palestinians.

Kushner, however, canceled his stop in Jerusalem, citing potential weather-related flight delays.

Plenty of other politicians did find their way into the solemn gathering, however. Macron caused a stir when he was shown shouting at Israeli security personnel as he was entering the Church of St. Anne, a medieval edifice owned by the French government. The vocal dispute apparently had to do with whether French or Israeli security would escort Macron into the nave, a reflection of the byzantine turf conflicts that riddle Jerusalem’s holy sites. (Control of the nearby Church of the Holy Sepulchre is divided among six Christian sects.)

Andrzej Duda, president of Poland, where Auschwitz and other Nazi concentration camps were located, boycotted the gathering in protest of not being offered a speaking role at the Yad Vashem ceremony. Duda will attend commemorative events at Auschwitz on Monday.

Locally, though, Israelis were fixated on Putin, particularly whether he would use his visit to announce the release of a 27-year-old American Israeli backpacker imprisoned in Russia on minor drug charges. The case is widely seen as part of a larger geopolitical tussle between Russia and the United States, including efforts by Washington to have an alleged Russian hacker extradited from Israel.

The plight of the New Jersey-born Na’ama Issachar, who was found with a small amount of hashish when transiting the Moscow airport on a flight from India, has become a cause celebre here. “Free Na’ama” signs hang over highways, and her mother has become a frequent, pleading presence on television.

Putin appeared with the mother Thursday after meeting Netanyahu at the prime minister’s residence, telling her that “everything will be fine” and promising to consider her request to let her daughter come home.

Pence also met with Netanyahu and with Benny Gantz, the former Israeli army chief who is Netanyahu’s main rival in a year-long political standoff. He invited both to Washington next week for a briefing on the administration’s long-awaited Israeli-Palestinian peace proposal, which could be released even as Israel ramps up for its third election in a year in March.

A potential fraught encounter looms for Pence in the person of Ukrainian President Volodymyr Zelensky, the leader at the center of impeachment proceedings in Washington. Pence skipped Zelenksy’s inauguration in May at a time when Trump was seeking to pressure the Ukrainian to investigate a Democratic rival.

Pence was also planning to visit the Western Wall in Jerusalem’s Old City with his wife, Karen. Putin was slated to visit the West Bank city of Bethlehem for a meeting with Palestinian Authority President Mahmoud Abbas.

Isabelle Khurshudyan in Moscow contributed to this report.