This article is part of The D.C. Brief, TIME’s politics newsletter. Sign up here to get stories like this sent to your inbox.As a mob infiltrated the U.S. Capitol on Jan. 6, 2021, House Speaker Nancy Pelosi was walking at a measured speed and talking with just as much purpose, descending level after level into the besieged building as her security detail sorted out the next steps out of there. What was supposed to be a routine ceremony had become one of the darkest days in American history. Despite the chaos unfolding around her, Pelosi never seemed like a leader in retreat. The steely resolve that would become her trademark was clearly visible in footage taken that day by her daughter, filmmaker Alexandra Pelosi.[time-brightcove not-tgx=”true”]“The proceedings are proceeding?” she asked her aides. “If they stop the proceedings, they will have succeeded in stopping the validation of the President of the United States. If they stop the proceedings, we will have totally failed.” Phoning through the top ranks of the government—leaders at the Pentagon and Department of Justice, Vice President Mike Pence, the Virginia Governor’s office—Pelosi marshaled all corners of Washington to get things back under control. “I worry about you being in that Capitol room,” she told Pence, who was trapped on a loading dock, hiding. “Don’t let anybody know where you are.” After the sun set and the mob had been purged, Pelosi returned to a Capitol in shambles to help complete the day’s task. Back at the Capitol, she declared: “We always knew that this responsibility would take us into the night and we will stay as long as it takes. Our purpose will be accomplished.” It’s that refusal to ever see a situation beyond her control that marked four extraordinary decades as the most powerful woman in U.S. politics. The first and only female to be Speaker of the House, Pelosi dictated the terms of Democratic politics for a generation, recruiting legions of loyalists and ushering in huge policy moves like Barack Obama’s health care overhaul, Joe Biden’s infrastructure investments, and both of Donald Trump’s impeachments. All the while she clocked $1.3 billion in fundraising, according to the tally her aides have kept over the years. Beloved by liberal partisans and loathed by their counterparts, Pelosi was one of the last engineers of an old-school political machine that could count votes better than anyone in a generation.“I will not be seeking reelection to Congress. With a grateful heart, I look forward to my final year of service as your representative,” the 85-year-old Pelosi said in a video released Thursday announcing that she would retire when her current term ends in early 2027.It was an exit the Speaker Emerita had signaled in recent weeks, but it was also a decision she alone could make. As she told CNN in an interview that aired earlier this week, she continued to wield power, even if it was softer than she had enjoyed not that long ago. “I have no doubt that if I decided to run, I would win,” Pelosi said. “That isn’t even a question.”Longtime Insider, First-Time CandidateNancy D’Alesandro was born into a longtime Democratic political machine in Baltimore, where her father was a member of the House and future Mayor, her brother also a future Mayor, and her mother her tutor in how to wield power from kitchen tables, front porches, and church halls. Pelosi grew up seeing that all politics is personal and a favor system could go a long way. It would shape her climb to politics, although she would not seek elected office until later in life.A former Hill intern—she worked alongside future rival Steny Hoyer—she was a natural organizer. She helped land the 1984 Democratic convention for San Francisco, husband Paul Pelosi’s hometown and her adoptive one. She rose through the state party’s ranks, picking up chits she could use for decades. She raised money for Senate Democrats during the 1986 cycle and went to Congress the following year in a special election. She was 47, and her five children were old enough to have a bicoastal parent.A Lawmaker Who Others Took SeriouslyIf the boys’ club of Washington expected Pelosi to arrive a nepobaby or dilettante housewife, they were quickly disabused of that. She used her first speech on the House floor to drive directly at the HIV/ AIDS challenges unfolding in San Francisco’s large LGBTQ community. “We must take the leadership of course in the crisis of AIDS,” she said. She worked with George H.W. Bush’s White House to pass the Ryan White Act, which provided resources for those living with HIV/ AIDS. And she landed plum seats on Appropriations and Intelligence committees. It was from her post on Intel that she watched the world change on Sept. 11, 2001. As the top Democrat on the panel, she had access to some of the nation’s biggest secrets as George W. Bush’s administration responded with the invasion of Afghanistan and the march toward Iraq. Pelosi backed the committee’s conclusion that the intelligence community never had specific intelligence that could have prevented the 9/11 attacks but balked at supporting Bush’s preparations to invade Iraq. Ultimately, she secured 126 votes against that resolution, besting the 81 Democrats who backed Bush. She would go on to become the longest serving member of House Intelligence in history. Madam SpeakerPelosi continued to rise in her party’s ranks, helping quarterback House Democrats’ successful 2006 campaign. Working with then-Rep. Rahm Emanuel, Pelosi recruited candidates that matched their districts and encouraged them to hone their strategy around winning above anything else. And it worked; Democrats picked up 31 seats and the House majority for the first time since 1995.In turn, Pelosi made history. As Bush returned to Congress the following year, he said, “Tonight I have a high privilege and distinct honor of my own, as the first President to begin the State of the Union message with these words: Madam Speaker.” As she would years later against Trump, Pelosi emerged as the Democrats’ most effective opposition leader against the Bush administration. That did not mean she was always spoiling for a fight. She shut down any talk of pulling funding for U.S. forces. Similarly, she cut down any talk of impeaching Bush, instead seeing the partisan move as a surefire way to ensure Republicans would hold the White House in 2008. In a way, Pelosi’s approach to the opposition leader role gave her more power than if she were simply a contrarian. In the final months of Bush’s term and with an economy on the brink of total meltdown, Pelosi gave her blessing for a Wall Street bailout that was as big as it was unpopular. But Pelosi understood the stakes. It didn’t hurt that Treasury Secretary Hank Paulson got down on one knee begging Pelosi to let the talks proceed. “I didn’t know you were Catholic,” Pelosi said dryly. The measure passed on a bipartisan basis.A Speaker Who Knew Her PowerIt is not an exaggeration to say Pelosi was the most effective Speaker of a generation. Comparisons going back to Tip O’Neill are not overblown, and it’s easy to see why when her record is laid on the table. She welcomed Obama to Washington with the largest majority in 15 years. Working with him, she ushered an economic stimulus bill into law to shore-up the post-2008 economy and muscled through Obamacare despite its deep unpopularity and zero votes from the GOP.But it came at a cost. In 2010, Democrats lost a net 63 seats, the biggest snapback since 1938. Still, Pelosi held control over her caucus and did not retreat to San Francisco. She was too prolific a fundraiser for the party to push out. Plus, she had a list of favors she still had piled high. As happened so often, lawmakers of all stripes have stories about walking into her office with a mind made up about an upcoming vote only to return to their offices to tell the staff there was another plan. Pelosi controlled her team with a gentle hand—until she needed to show force.Pivot on ImpeachmentWhile Pelosi watched Trump’s improbable rise and move to the White House, she publicly rejected calls to impeach him. “He’s just not worth it,” she said in 2019. But that changed later that year. Back in the Speaker’s suite after eight years in the minority, she watched as proof emerged of Trump holding up aid for Ukraine unless leaders there agreed to dig up dirt on Joe Biden, a leading contender for the nomination in 2020. Suddenly, Pelosi was of a different mind, overseeing not one but two impeachment trials before Trump left office on Jan. 20, 2021. The second came in the aftermath of Jan. 6. In both cases, the GOP-led Senate voted to acquit. Biden’s Partner—Until a Bad DebateBiden’s return to Washington came with Pelosi in charge again, and she wasted no time notching big wins on COVID, stimulus, and infrastructure, as well as the nation’s largest investment ever in clean energy. And his semiconductor law jumpstarted the tech sector in a major way that’s still reverberating. At times, Pelosi had a majority as small as four votes and at others had to acquiesce to parochial demands of Democratic Senators in a 50-50 Upper Chamber. In 2018, Pelosi recognized the tumult in her caucus and pledged she would cede her role atop the Democratic leadership ladder in four years’ time. She followed through in 2022, settling into an emeritus role and something of a minister without portfolio. But she had one final flex in store. As calls grew last summer for Biden to forgo his re-election bid after a particularly bad debate performance, and Biden was proving typically stubborn, Pelosi took control of the situation in a way few others could. “It’s up to the President to decide if he is going to run,” she said in a carefully worded answer on Morning Joe that resounded around Washington. Biden thought he had already decided to stay in the race. Pelosi had other ideas. And like so many times before, Pelosi had control.Make sense of what matters in Washington. Sign up for the D.C. Brief newsletter.