On a stage in Los Angeles last week, two Israeli-born women sat before a rapt audience, discussing their grief and anger in the wake of the Oct. 7 attack on Israel by Hamas terrorists. More than 500 people had crowded into a synagogue auditorium to listen, and 400 more tuned in via Zoom.

“We’re actually seeing the horrors that our grandparents told us about,” Noa Tishby, Israel’s former special envoy for combating antisemitism, told them. “We’re seeing them manifesting in reality.”

Joining her was Gal Gadot, who starred in the blockbuster film “Wonder Woman,” among others. But in this perilous moment, it is Ms. Tishby, 48, who is drawing the attention of American Jews, television news shows and, most of all, social media.

Once the love-to-hate-her villain of a popular Israeli television drama, Ms. Tishby moved to Los Angeles hoping for a career trajectory like the one Ms. Gadot would find — an Israeli actress and model who became famous as a Hollywood supercelebrity.

Instead, she has become a dominant and provocative voice on a war that is being fought in the Middle East and also on television, social media, and American streets and college campuses.

Ms. Tishby is an unabashed booster of Israel who describes herself as “pro-Palestinian, just anti-Hamas.” She speaks forcefully against a cease-fire in Gaza and against U.S. students and others who have rallied in support of the attack on Israel. Her mission, she says, is to combat global antisemitism and the digital spread of misinformation. To her critics, she can sound like an apologist for the Israeli government.

In the three weeks since the war between Israel and Hamas began, she has been, seemingly, everywhere.

Ms. Tishby’s 2021 book, “Israel: A Simple Guide to the Most Misunderstood Country on Earth,” hit the New York Times paperback best-seller list for the first time last month and recently rose to No. 4.

She has appeared on Fox News, CNN and MSNBC’s “Morning Joe.” And she has gained several hundred thousand followers on Instagram since she first broadcast the news that Hamas terrorists had made their way into Israel. When you ask pro-Israel Jewish Americans if they are following Ms. Tishby’s posts, there is a frequent reply: “I’m obsessed.”

At a time when Jewish people who were raised to revere Israel are feeling stunned by what they see as a lack of empathy from a progressive left they have supported and from universities they attended, Ms. Tishby has emerged as a north star. “She is the voice of this Jewish generation,” said Yoav Davis, who created the popular Jews of NY Instagram account and works closely with Ms. Tishby on her digital content. “I keep telling her that God has been grooming her for this moment.”

The overarching theme of her message is this: When people reject Zionism, suggesting that Israel does not have the right to exist as a Jewish state, it is code for hatred of Jews themselves. “When a massacre occurs that is more barbaric than the world had seen in generations, people actually say, ‘Well, but Israel kind of deserves that,’” Ms. Tishby said. “Anti-Zionism is antisemitism.”

That concept — that anti-Zionism and antisemitism are equivalent — is at the heart of a generations-long argument. It is a position endorsed by many mainstream organizations and rejected by others, including many progressive Jews. Critics say that tying a disavowal of Zionism to antisemitism discourages critical discourse about Israeli policy.

“My overarching critique of Noa is that she is part of an effort that is led by the Israeli government to conflate all strident criticism of Israeli governmental policy with antisemitism,” said Simone Zimmerman, a writer and activist who helped create “If Not Now,” a movement of American Jews who are critical of the Israeli government for its policies toward Palestinians.

Ms. Tishby, who said she was fired by the Israeli government after criticizing the Netanyahu administration, says she welcomes the debate. But she does not apologize for her belief that her homeland has a right to defend itself, even now, when Israel is facing intense criticism for its barrage on areas of Gaza populated both by civilians and Hamas.

“Three weeks ago, Israel was brutally attacked by savages who are out to destroy her,” she said. “If Mexico would have done the same thing to the United States, nobody would have told the U.S. three weeks in ‘restrain yourself.’ Israeli is doing the best it can in an impossible situation.”

She demurs only when she is asked if she stands behind Prime Minister Benjamin Netanyahu and his handling of the war. “I don’t want to talk about that,” she said.

In social media videos and in interviews, Ms. Tishby speaks with the ease of a veteran broadcast anchor, the self-certainty of a politician who has honed her talking points and the passion of an activist who is willing to reveal her emotions but not give in to them.

Her objective, she said, is to lift the morale of Jewish people around the world and to try to reach those on the political left who believe the killing of 1,400 Israelis and kidnapping of 240 more by Hamas was an act of Palestinian resistance. “The progressive left has been played,” she said.

In an appearance on Fox last week with Sean Hannity, Ms. Tishby noted that Hamas has broken cease-fires in the past, and she emphasized the threat posed by Iran, a supporter of Hamas. “The human rights that you have in Iran are the human rights that you are going to have in the West” if Hamas is not removed from power, she said. “Israel is fighting the West’s war.”

And in an Instagram video post that included footage of the plane that crashed into the World Trade Center, Ms. Tishby spoke to the camera. “Imagine if within days of the Al Qaeda attack on 9/11,” she said, “a group of students on American campuses were holding rallies in support of that terror attack.” She added: “That is exactly what is happening on campuses in America right now.”

To plenty of Jewish people, Ms. Tishby is an inspiration — a frontline general in a messaging war, providing supporters of Israel with an insider understanding of its history and answers to accusations made about a country they cherish — all in shareable Instagram posts. “She is a pro-Israel influencer on a platform that is notoriously hostile to Israel,” said Representative Ritchie Torres, a Democrat from New York and a close friend. “The common refrain that I’ve heard from the Jewish community is, ‘We’re feeling alone and we’re feeling scared, and it’s voices like Noa Tishby’s that make us feel less alone and scared.’”

Before the war, Ms. Tishby was relatively unknown in the United States. But for decades, “she was a household name in Israel,” said her friend Gideon Raff, who created the Israeli television series “Prisoners of War” and was an executive producer of “Homeland,” the Showtime series based on it.

Ms. Tishby was born in Tel Aviv and raised in a politically active, progressive family. She served in the Israel Defense Forces, in what might be thought of as the Israeli U.S.O. She traveled from “the Golan Heights to Hebron to the Gaza Strip,” she wrote in her book, singing cover tunes and performing sketches for her fellow soldiers.

While still in the army, she was cast in a television drama as Dafna Maor, a designer hired to bring youth and relevance to a fashion company. The show, named “Ramat Aviv Gimmel,” for an affluent suburb of Tel Aviv, was a sensation.

Ms. Tishby, who was also a pop singer, moved to Los Angeles about 20 years ago but was frustrated by the difficulties of building an acting and singing career in Hollywood. And she found herself startled by what she perceived as some Americans’ relative ignorance of geopolitics and Israeli history.

People would criticize Israel, “and I would ask them a simple question like, do they understand the difference between Hamas and the Palestinian Authority or where Gaza is?” she said. “They wouldn’t have a clue.”

Ms. Tishby became “the nonofficial Israel explainer among my friends and my colleagues,” she said.

Professionally, she pivoted. She brought the popular Israeli show “BeTipul,” to American television, where it became “In Treatment” on HBO, starring Gabriel Byrne, and she became an executive producer.

She also developed a robust side-hustle as an activist. She started a rapid-response digital platform to address misinformation she believed was going unaddressed by the Israeli government. She sat on panels and delivered speeches, seeing her life’s mission evolve.

In 2021, she published “Israel,” a primer on the country’s ancient past and recent history.

Ms. Tishby is a good talker and keeps her writing conversational too. After laying out 3,000 years of Jewish struggle in about 20 pages, she writes, “All these ancient and dramatic events happened on the exact same land where Israel is located today. I don’t believe this because of religious credo but because of archaeology, science and history. This isn’t about God, so let’s leave her out of it.”

The next year, Ms. Tishby became Israel’s first official representative in the fight against antisemitism, appointed by Yair Lapid, who was then Israel’s foreign minister.

“Israel as a country had failed miserably in this new world at realizing that a new generation didn’t have the attention for the memory of the Holocaust to be told by the old generation,” said Mr. Lapid, who is now the Israeli government’s opposition leader.

He told his staff, “Let’s not appoint another aging diplomat but someone who is smart and beautiful and is a great communicator and has the ability to speak the language of the new world.”

The job title, “special envoy for combating antisemitism and delegitimization,” made official what Ms. Tishby was already doing, she said.

It gave her new entree — last September, she testified at the U.S. Capitol — but it also opened her to heightened criticism, particularly after the death of the Palestinian journalist Shireen Abu Akleh.

Ms. Abu Akleh was killed while covering a gunfight between Palestinians and Israeli forces in the West Bank in May 2022. The Israeli government initially suggested Palestinians were responsible, then said it was possible she was hit in Israeli crossfire. After conducting an independent investigation, a United Nations committee recently found the Israeli security forces responsible, saying they used “lethal force without justification.”

In the aftermath, Ms. Tishby said that anger directed at Israel was unfair. “Journalists are killed around the world every week, without the same global reaction,” she posted on social media. “This is the antisemitic double standard.”

Ms. Tishby’s official job was short-lived. Early this year, after the Netanyahu administration announced plans to weaken the power of the judiciary, Ms. Tishby criticized the proposal in speeches and writing.

Mr. Lapid, who served a short stint as prime minister until voters reinstated Mr. Netanyahu late last year, told her, “You know they’re going to fire you.”

“ ‘I don’t care,’” he said Ms. Tishby replied.

She continued her work, minus the title, speaking publicly about what a growing tide of antisemitism could mean for Israel. Then, as she sat at a friend’s house after Shabbat dinner on Oct. 6 in Los Angeles — early in the morning of Oct. 7 in Israel — her phone began to buzz. She raced home and began broadcasting on Instagram, translating Israeli news reports in real time. She was among the first to share videos of terrorists in Israel.

Now, in response to anti-Israel demonstrations, she is redoubling her efforts to urge Jewish parents to give their children a solid education in Israel’s history.

She believes the Jewish community should be talking about Israel’s complicated past and contemporary issues, “even if they’re uncomfortable,” she said. “The justification for the existence of a Jewish state does not require us to hide anything.”

In Los Angeles last week, Ms. Tishby began her event with Ms. Gadot by asking the actress where she was when she first heard of the Hamas attack and how she was feeling.

“I’m happy to be alive because nowadays it’s not something to be taken for granted,” Ms. Gadot answered, her voice breaking with emotion.

Ms. Gadot posed the same question to Ms. Tishby. How was she feeling? Her answer came without hesitation: “I’m pissed off.”