WASHINGTON — Ron Klain, the White House chief of staff, gave a pep talk early on Feb. 18 at the daily gathering of the president’s most senior aides: The next 10 days, he said, will be the most consequential of the Biden presidency.

President Biden’s military and intelligence chiefs had told him that a Russian invasion was all but inevitable. Mr. Klain, a veteran of Washington and one of Mr. Biden’s closest advisers, also reminded them of what they already knew: A coming land war in Europe was about to collide with some of the most critical moments of Mr. Biden’s time in office.

The president had completed his review of candidates for the Supreme Court and was determined to make the announcement by week’s end. The Centers for Disease Control and Prevention was about to unveil guidelines that would herald a new phase of the pandemic that had dogged him during the first year of his presidency. And Mr. Biden needed to start practicing for his first State of the Union speech, just 11 days away.

All presidents are confronted by episodes that are out of their control, forced to react to the world around them more often than they are able to shape it. But the dizzying events of the past week have for now pushed to the sidelines the congressional squabbling over Mr. Biden’s domestic agenda, and are already redefining the arc of his presidency.

This account is based on interviews with a dozen current and former administration officials, most of whom agreed to describe internal deliberations on the condition of anonymity.

Mr. Biden’s aides say his actions in recent days were an example of the caution and consensus-building that have always been at the heart of his sales pitch to voters. In his State of the Union address on Tuesday, Mr. Biden is expected to focus on inflation and the still-recovering economy, a primary concern to the public.

But drafts of the speech have been revised repeatedly throughout the week to take account of Mr. Biden’s challenge to President Vladimir V. Putin of Russia and the sweep of events in Europe, all with an eye firmly fixed on Mr. Biden’s place in history.

Since Mr. Klain’s staff meeting, Mr. Putin started the biggest land war in Europe in 70 years, Mr. Biden named Judge Ketanji Brown Jackson to become the first Black female justice in the Supreme Court’s 232-year history, and the C.D.C. announced new rules aimed at returning the country to something closer to normal.

“Whatever you do, you are always at the mercy of events somewhere in the world,” said David Axelrod, a top adviser to former President Barack Obama. “This period is a vivid example of it.”

Sunday, Feb. 20

If there was one message that Mr. Biden wanted to reinforce for his National Security Council in the Situation Room on Sunday morning, it was that the United States remained “in lock step with allies and partners,” as Secretary of State Antony J. Blinken put it later.

That desire was at the core of the American response that Mr. Biden had devised with Mr. Blinken; Jake Sullivan, his national security adviser; and others. The results would become clear soon enough, as Mr. Biden’s team repeatedly waited for European nations to issue sanctions before following suit.

Diplomacy, including a 15-minute call between Mr. Biden and President Emmanuel Macron of France, had done little to calm Ukraine’s president, Volodymyr Zelensky, who had grown frustrated by Mr. Biden’s warnings of an invasion. On the way back from the Munich Security Conference on Sunday, Vice President Kamala Harris spoke to Mr. Biden from Air Force Two.

She had repeated to Mr. Zelensky that the United States believed a Russian invasion was imminent, she told Mr. Biden. And she had assured Ukraine’s president that the administration was ready to issue economic penalties along with its European allies.

But questions of war and diplomacy gave way — briefly — to issues of public health. That afternoon, Dr. Anthony S. Fauci, Mr. Biden’s top public health adviser, arrived with some good news: We might finally be able to take off our masks.

Mr. Biden had been under increasing pressure from Democratic governors to address the anxiety among voters exhausted by the restrictions. But, as he had promised, he was waiting for the C.D.C. Federal health officials had been working for weeks on guidance that suggests that 70 percent of Americans would be able to stop wearing masks, the beginning of a transition from a pandemic to an endemic disease that would become a part of everyday life.

But on that Sunday, he had little time to dwell on the pandemic. By later in the afternoon, aides had ushered him into the State Dining Room, where a lectern was waiting. It was his first opportunity to practice an early draft of his State of the Union address.

Monday, Feb. 21

The president on Monday watched Mr. Putin deliver a rambling speech in which he repeated his grievances. The Russian leader warned that if Ukraine did not back down, it would be responsible for “the possibility of a continuation of bloodshed.”

Mr. Biden, a student of international conflict and diplomacy, had two reactions, according to people who talked to him about the speech.

It was grim confirmation of the assessments made by his military and intelligence officials, who had believed for weeks that Mr. Putin was likely to follow through on his threats against Ukraine. In that way, the Russian march toward war in Europe was hardly a surprise.

But he was still shocked, Mr. Biden told one of his top aides as they sat in the Oval Office discussing Mr. Putin’s speech.

That evening, Mr. Biden took a brief break to sit shiva, via Zoom, paying his respects to his daughter-in-law’s mother, who had passed away. Throughout the week, Mr. Biden would juggle calls from his family members as they grieved, officials said, sometimes between national security debates and meetings with world leaders.

Later on Monday, Mr. Biden and his aides debated whether Mr. Putin’s speech amounted to the beginnings of an invasion, a phrase the president and U.S. officials had avoided throughout. In the end, they agreed to put Jon Finer, a deputy national security adviser, on television to use that wording.

Mr. Putin’s speech made it clear to the president that war was inevitable.

“This guy’s really going to do it,” Mr. Biden told one of his top advisers.

Wednesday, Feb. 23

By Wednesday evening, the situation in Ukraine was grim. Mr. Biden, in the Oval Office later than usual, took calls from Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff, and Lloyd J. Austin III, the defense secretary. Russian troops were moving in ways that had not been seen before, even just hours earlier.

At the Pentagon, officials told reporters they believed a full-scale invasion of Ukraine could begin by 6 p.m., and some top officials could be seen checking their watches frequently.

The push for more severe sanctions continued throughout the day. For more than a year, Mr. Biden had been hesitant to use sanctions to shut down a key Russian natural gas pipeline known as Nord Stream 2, which was vital to Germany. But on Tuesday, Germany had halted the project, a sign that it was united behind tough sanctions, even if it meant severe consequences at home. Mr. Biden ordered sanctions on the company behind the pipeline, too.

Mr. Biden spent the rest of the evening bracing for a new European war in the Treaty Room, the ornate second-floor room in the White House residence where President William McKinley oversaw the signing of the peace treaty in 1898 that ended the Spanish-American War.

It came just after 10 p.m. Eastern time.

Within minutes, Mr. Biden was on the phone with Mr. Zelensky. The president shared the latest intelligence on Russia’s advance and asked Mr. Zelensky a simple question, according to a person familiar with the call: “What can we do for you?”

Mr. Zelensky urged Mr. Biden to tell the world to speak out against the invasion, and to impose sanctions on Russia.

Mr. Biden was up past midnight editing a statement on his call with Mr. Zelensky, determined to make sure the tone was right.

He also needed to decide about his Supreme Court nominee. He had promised to announce his pick by the end of the month, and that was only days away.

He wanted one more night to sleep on it, one of his top aides recalled.

Friday, Feb. 25

Unveiling a Supreme Court nominee felt like time slowed down, one senior White House adviser said.

Hours earlier, Mr. Biden had participated in a virtual NATO summit from the Situation Room, where flags of each nation had been put around the room the night before. Ukraine’s president had issued a plea for more help. “We’re defending our country alone. The most powerful forces in the world are watching this from a distance,” he said, insisting that sanctions had done little.

But as Mr. Biden began speaking at 2:02 p.m. on Friday — with Judge Jackson and Ms. Harris creating a historic tableau behind him — concerns about the war raging 4,800 miles away seemed to briefly fade.

In the days leading up to the announcement, there had been a constant churn of drafts being presented to the president: One team worked on statements for each Supreme Court nominee, another team for the State of the Union address and a third for his various remarks on the crisis in Ukraine.

The president had finished his review of candidates days earlier, though he had not told anyone his final decision, in part to prevent leaks. He gathered input from Ms. Harris, who interviewed each potential nominee one by one over Zoom calls. Thursday evening, in a call from the Treaty Room, Mr. Biden offered the job to Judge Jackson.

“I’d like you to go to the Supreme Court. How about that?” he told her, according to a video of the call he posted to Twitter.

The White House had been prepared to stage the announcement any day that week, though Mr. Biden had expressed a desire to do it on Friday, two years to the day after he pledged on the campaign trail to name the first Black woman to the court, one official said.

Mr. Biden and his team were greeted with applause by White House staff members gathered in the State Dining Room. But there was little time to embrace the moment for a president who was in desperate need of a win on his domestic agenda and was still reviewing drafts of his State of the Union address.

Mr. Biden was soon back up in the Treaty Room on the second floor of the White House residence with Mr. Sullivan, Mr. Klain and others.

For days, the president had resisted pressure to impose sanctions on Mr. Putin directly because it was not clear that European leaders were willing to take that step. But now, there were news reports that some European capitals were doing just that. In a series of phone calls, Mr. Biden confirmed with his counterparts that they were willing to punish Mr. Putin and his relatives.

He picked up the phone and called Jen Psaki, the White House press secretary, who had a statement ready.

“Go ahead,” he said.

Saturday, Feb. 26

Mr. Biden spent Saturday at his home in Wilmington, Del., preparing to face Congress on Tuesday during his State of the Union address.

Fighting remained intense in Ukraine as Russian forces pushed toward the capital city. One thousand eight hundred and seventy-two people died of Covid. And Judge Jackson began preparations with White House advisers for what some expect to be a contentious confirmation battle.

It was a reminder, as one aide to Mr. Biden put it, that “this is just the beginning.”

David E. Sanger contributed reporting.