This was not the speech she expected to give, at least not on this day. Yulia Navalnaya had come to a gathering of world leaders in Munich to press them to remember her imprisoned husband and her troubled country.
And then just as the conference opened on Friday morning came word from Russian state media that her husband, the crusading, defiant dissident Aleksei A. Navalny, was dead in one of President Vladimir V. Putin’s prisons.
By her own admission, her first thought was to fly away, to join her grown children to mourn in private a man who had already survived a horrific poisoning and years behind bars. But before she did, she decided she had to speak out. Because he would have wanted her to.
Ms. Navalnaya stunned the presidents, prime ministers, diplomats and generals at the Munich Security Conference when she strode into the hall on Friday afternoon, took the stage and delivered an unflinching condemnation of Mr. Putin, vowing that he and his circle would be brought to justice. Her dramatic appearance electrified a conference already consumed with the threat posed by a revanchist Russia.
“I don’t know whether to believe the news or not, the awful news that we receive only from government sources in Russia,” she told the high-powered audience, which hung on her every word. “We cannot believe Putin and Putin’s government. They’re always lying.”
“But if this is true,” she went on, speaking in Russian, “I want Putin and everyone around him, Putin’s friends, his government, to know that they will bear responsibility for what they have done to our country, to my family and to my husband. And this day will come very soon.”
“And I want to call on the world community,” she continued, “everyone in this room and people around the world to come together to defeat this evil, defeat this horrible regime that is now in Russia.”
Ms. Navalnaya spoke clearly and calmly, with no notes but remarkable composure, her face etched with evident pain. Standing at the lectern, she clasped her hands in front of her and stared straight ahead as if willing herself to focus on her message. She was dressed in the professional pantsuit she had brought for what she thought would be a couple of days of lobbying, her hair pulled back, her makeup perfect. She appeared determined to show no weakness.
She spoke for just two minutes, but it captivated the audience, which included Vice President Kamala Harris sitting in the front row and Secretary of State Antony J. Blinken up in the balcony. The crowd rose to its feet to give her an emotional standing ovation, and Representative Nancy Pelosi, the former House speaker, reached out as Ms. Navalnaya left the stage to kiss her as a couple of senators looked on.
“On what must be the worst day of her life, she was so strong, and a reminder that Russians who believe in freedom will continue to fight for as long as it takes to hold Putin accountable for his barbaric crimes,” Michael A. McFaul, a former ambassador to Russia, said of Ms. Navalnaya after her speech.
In the annals of international meetings, it would be hard to remember a more riveting moment, when the careful choreography and scripted speeches laden with diplomatic jargon fall to the wayside as life-or-death questions play out in such personal fashion. The leaders gathered in Munich were already consumed about what to do about Russia, but the news added fresh urgency to the conversations.
Ms. Harris had come to give a speech about the dangers of going soft on Russia at a time when House Republicans are blocking aid to Ukraine and former President Donald J. Trump is boasting that he would “encourage” Russia to attack NATO allies that do not spend enough on their own militaries.
In the minutes before her address, she and her staff heard the news about Mr. Navalny, scrambled to learn what they could and quickly updated her text to reflect outrage.
“If confirmed, this would be a further sign of Putin’s brutality,” she told the conference, words later echoed by President Biden back in Washington. “Whatever story they tell, let us be clear: Russia is responsible.”
She went on to deliver the message she had hoped to impart, that the United States remains committed to its allies and to American leadership in the world. Without naming him, she castigated Mr. Trump for seeking “to isolate ourselves from the world,” “to embrace dictators and adopt their repressive tactics” and to “abandon commitments to our allies.”
“Let me be clear,” she said. “That worldview is dangerous, destabilizing and, indeed, shortsighted. That view would weaken America and would undermine global stability and undermine global prosperity.”
Afterward, Ms. Harris and Mr. Blinken each met separately with Ms. Navalnaya to express their condolences and commitment.
Ms. Navalnaya had come to Munich along with Leonid Volkov, her husband’s longtime chief of staff, to keep world leaders focused on her husband’s case and the clampdown on dissent by Mr. Putin’s government. She mingled on Thursday evening with conference attendees, seeing them at dinner and describing how conditions had worsened for her husband since they transferred him to a different prison in the Arctic.
“He had hardly any contact with other people,” Mr. McFaul said she told him. “His outdoor walking space was actually just another cell adjacent to him with no roof. They limited severely what he could read and piped in Putin speeches on a radio channel that had only one channel. It sounded like horrific torture.”
Over the years, many Russians hoped that Ms. Navalnaya might step in to become an alternative leading figure in the opposition. While fiercely outspoken in defending her husband and criticizing the many forms of oppression that he faced, however, she has never ventured directly into opposition politics — and rarely took to a podium as she did in Munich.
During Mr. Navalny’s time in Germany, where he was treated after his poisoning in 2020, she remained private, posting only occasional photos of the two of them together during his treatment and recovery, but never speaking publicly.
She became familiar to tens of millions around the world last year, however, when she appeared at the Academy Awards ceremony, where the documentary “Navalny” won an Oscar. In an interview afterward with Der Spiegel, the German news outlet, she expressed worry for her husband’s health in prison and lamented that she might never get to see him in person again.
“We all understand that it is Putin personally who is keeping Aleksei in prison,” she said then, “and as long as he stays in power, it is hard to imagine that Aleksei will be released.”
Mr. Navalny had continued to post on social media from prison by passing messages to his visiting lawyers. His most recent Instagram post was on Wednesday — Valentine’s Day — and it was a message to Yulia: We may be separated by “blue blizzards and thousands of kilometers,” he wrote, “but I feel that you are near me every second, and I keep loving you even more.”
Anton Troianovski and Melissa Eddy contributed reporting.