March 2016

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May 2016

June 2016

On an October afternoon before the 2016 election, a huge banner was unfurled from the Manhattan Bridge in New York City: Vladimir V. Putin against a Russian-flag background, and the unlikely word “Peacemaker” below. It was a daredevil happy birthday to the Russian president, who was turning 64.

In November, shortly after Donald J. Trump eked out a victory that Moscow had worked to assist, an even bigger banner appeared, this time on the Arlington Memorial Bridge in Washington: the face of President Barack Obama and “Goodbye Murderer” in big red letters.

Police never identified who had hung the banners, but there were clues. The earliest promoters of the images on Twitter were American-sounding accounts, including @LeroyLovesUSA, later exposed as Russian fakes operated from St. Petersburg to influence American voters.

The Kremlin, it appeared, had reached onto United States soil in New York and Washington. The banners may well have been intended as visual victory laps for the most effective foreign interference in an American election in history.

For many Americans, the Trump-Russia story as it has been voluminously reported over the past two years is a confusing tangle of unfamiliar names and cyberjargon, further obscured by the shout-fest of partisan politics. What Robert S. Mueller III, the special counsel in charge of the investigation, may know or may yet discover is still uncertain. President Trump’s Twitter outbursts that it is all a “hoax” and a “witch hunt,” in the face of a mountain of evidence to the contrary, have taken a toll on public comprehension.

But to travel back to 2016 and trace the major plotlines of the Russian attack is to underscore what we now know with certainty: The Russians carried out a landmark intervention that will be examined for decades to come. Acting on the personal animus of Mr. Putin, public and private instruments of Russian power moved with daring and skill to harness the currents of American politics. Well-connected Russians worked aggressively to recruit or influence people inside the Trump campaign.

To many Americans, the intervention seemed to be a surprise attack, a stealth cyberage Pearl Harbor, carried out by an inexplicably sinister Russia. For Mr. Putin, however, it was long-overdue payback, a justified response to years of “provocations” from the United States.

And there is a plausible case that Mr. Putin succeeded in delivering the presidency to his admirer, Mr. Trump, though it cannot be proved or disproved. In an election with an extraordinarily close margin, the repeated disruption of the Clinton campaign by emails published on WikiLeaks and the anti-Clinton, pro-Trump messages shared with millions of voters by Russia could have made the difference, a possibility Mr. Trump flatly rejects.

As Mr. Trump emerged in spring 2016 as the improbable favorite for the Republican nomination, the Russian operation accelerated on three fronts — the hacking and leaking of Democratic documents; massive fraud on Facebook and Twitter; and outreach to Trump campaign associates.

Consider 10 days in March. On March 15 of that year, Mr. Trump won five primaries, closing in on his party’s nomination, and crowed that he had become “the biggest political story anywhere in the world.” That same day in Moscow, a veteran hacker named Ivan Yermakov, a Russian military intelligence officer working for a secret outfit called Unit 26165, began probing the computer network of the Democratic National Committee. In St. Petersburg, shift workers posted on Facebook and Twitter at a feverish pace, posing as Americans and following instructions to attack Mrs. Clinton.

On March 21 in Washington, Mr. Trump announced his foreign policy team, a group of fringe figures whose advocacy of warmer relations with Russia ran counter to Republican orthodoxy. Meanwhile, Unit 26165 was poring over the bounty from a separate attack it had just carried out: 50,000 emails stolen from the Clinton campaign’s chairman.

On March 24, one of the members of the Trump foreign policy team, George Papadopoulos, sat in the cafe of an upscale London hotel with a Russian woman who introduced herself as Mr. Putin’s niece and offered to help set up a meeting between the Russian president and Mr. Trump. The woman and the adviser exchanged frequent messages in the weeks that followed. Today, Mr. Padadopoulos is unsure that those messages came from the person he met in the cafe.

The Russian intervention was essentially a hijacking — of American companies like Facebook and Twitter; of American citizens’ feelings about immigration and race; of American journalists eager for scoops, however modest; of the naïve, or perhaps not so naïve, ambitions of Mr. Trump’s advisers. The Russian trolls, hackers and agents totaled barely 100, and their task was to steer millions of American voters. They knew it would take a village to sabotage an election.

Russians or suspected Russian agents — including oligarchs, diplomats, former military officers and shadowy intermediaries — had dozens of contacts during the campaign with Mr. Trump’s associates. They reached out through email, Facebook and Twitter. They sought introductions through trusted business connections of Mr. Trump’s, obscure academic institutions, veterans groups and the National Rifle Association.

They met Trump campaign aides in Moscow, London, New York and Louisville, Ky. One claimed the Russians had “dirt” on Hillary Clinton; another Russian, the Trump campaign was told, would deliver it. In May and June alone, the Trump campaign fielded at least four invitations to meet with Russian intermediaries or officials.

In nearly every case, the Trump aides and associates seemed enthusiastic about their exchanges with the Russians. Over months of such probing, it seems that no one alerted the Federal Bureau of Investigation to the foreign overtures.

Mr. Trump’s position on the Russian contacts has evolved over time: first, that there were none; then, that they did not amount to collusion; next, that in any case collusion was not a crime. That is mere semantics — conspiracy is the technical legal term for abetting the Russians in breaking American laws, such as those outlawing computer hacking and banning foreign assistance to a campaign.

Whether Mr. Trump or any of his associates conspired with the Russians is a central question of the investigation by Mr. Mueller, who has already charged 26 Russians and won convictions or guilty pleas from the former national security adviser, Michael T. Flynn; the former campaign chairman, Paul J. Manafort, and his deputy, Rick Gates; and from Mr. Papadopoulos. Mr. Trump’s personal lawyer, Michael D. Cohen, has pleaded guilty in a separate case.

But none of the convictions to date involve conspiracy. There remains an alternative explanation to the collusion theory: that the Trump aides, far from certain their candidate would win, were happy to meet the Russians because they thought it might lead to moneymaking deals after the election. “Black Caviar,” read the subject line of an email Mr. Manafort got in July 2016 from his associate in Kiev, Ukraine, hinting at the possibility of new largess from a Russian oligarch with whom they had done business.

Nina L. Khrushcheva, a professor of international affairs at the New School and the great-granddaughter of the Soviet premier Nikita S. Khrushchev, said that what Russia pulled off, through creativity and sheer luck, would have been the envy of Mr. Putin’s predecessors: puncturing the American sense of superiority and insisting on Russia’s power and place in the world.

“This operation was to show the Americans — that you bastards are just as screwed up as the rest of us,” Professor Khrushcheva said. “Putin fulfilled the dream of every Soviet leader — to stick it to the United States. I think this will be studied by the K.G.B.’s successors for a very long time.”

See the full timeline of events.

The Russian leader thought the United States, and Hillary Clinton, had sought to undermine his presidency.

The first Russian advance party was tiny: two women on a whirlwind American tour. Hitting nine states in three weeks in summer 2014, Anna Bogacheva and Aleksandra Krylova were supposed to “gather intelligence” to help them mimic Americans on Facebook and Twitter. They snapped photos and chatted up strangers from California to New York, on a sort of Russian “Thelma & Louise” road trip for the era of social media.

Even then, federal prosecutors would later say, the Russian government was thinking about the next United States presidential election — perhaps ahead of most Americans. Ms. Bogacheva and Ms. Krylova had been dispatched by their employer, an online propaganda factory in St. Petersburg, to prepare to influence American voters.

But why did Mr. Putin care about the election, then more than two years away? He was seething. The United States, in his view, had bullied and interfered with Russia for long enough. It was high time to fight back.

His motives were rooted in Russia’s ambivalence toward the West, captured in the history of St. Petersburg, Russia’s spectacular northern city and Mr. Putin’s hometown. Peter the Great, the brutal but westward-looking 18th-century czar, had brought in the best Italian architects to construct Russia’s “window on Europe” in a swamp.

Czar Peter’s portrait replaced Vladimir Lenin’s in Mr. Putin’s office when he took a job working for the city’s mayor in the early 1990s. Twenty-five years later, the internet offered a different kind of window on the West — a portal that could be used for a virtual invasion.

Mr. Putin, a former K.G.B. officer, had described the breakup of the Soviet Union as the “greatest geopolitical catastrophe” of the 20th century, a remarkable statement from a man whose country experienced revolution, civil war, bloody purges and the deaths of 27 million people in World War II. Like many of his fellow citizens, Mr. Putin was nostalgic for Russia’s lost superpower status. And he resented what he saw as American arrogance.

The Russian leader believed the United States had relentlessly sought to undermine Russian sovereignty and his own legitimacy. The United States had backed democratic, anti-Russian forces in the so-called color revolutions on Russia’s borders, in Georgia in 2003 and Ukraine in 2004. It had funded pro-democracy Russian activists through American organizations with millions in State Department grants each year.

With little evidence, Mr. Putin believed this American meddling helped produce street demonstrations in Moscow and other cities in 2011, with crowds complaining of a rigged parliamentary election and chanting, “Putin’s a thief!”

And Mrs. Clinton, then secretary of state, cheered the protesters on. Russians, she said, “deserve the right to have their voices heard and their votes counted, and that means they deserve free, fair, transparent elections and leaders who are accountable to them.”

Mr. Putin blamed Mrs. Clinton for the turmoil, claiming that when she spoke out, his political enemies “heard the signal and with the support of the U.S. State Department began active work.”

The two tangled again the next year when Mr. Putin pushed for a “Eurasian Union” that would in effect compete with the European Union. Mrs. Clinton sharply dismissed the notion, calling it a scheme to “re-Sovietize the region” and saying the United States would try to block it.

By 2013, with his initial hopes for a “reset” of Russian relations dashed, Mr. Obama, like his top diplomat, no longer bothered to be diplomatic. He criticized Russia’s anti-gay legislation, part of Mr. Putin’s effort to become a global champion for conservative values, and gave a biting description of the Russian leader: “He’s got that kind of slouch, looking like the bored kid in the back of the classroom.” Mr. Putin was reported to be furious.

After Russian troops seized Crimea and carried out a stealth invasion of Ukraine in 2014, relations grew openly hostile. American support for the new government in Kiev and condemnation of Russian behavior heightened Mr. Putin’s rage at being told what he could do and not do in what he considered his own backyard.

If Russia had only a fraction of the United States’ military might and nothing like its economic power, it had honed its abilities in hacking and influence operations through attacks in Eastern Europe. And it could turn these weapons on America to even the score.

By making mischief in the 2016 election, Mr. Putin could wreak revenge on his enemy, Mrs. Clinton, the presumed Democratic nominee, damaging if not defeating her. He could highlight the polarized state of American democracy, making it a less appealing model for Russians and their neighbors. And he could send a message that Russia would not meekly submit to a domineering America.

Hence the two Russian women who toured the United States in 2014, keyboard warriors granted the unusual privilege of real-world travel, hitting both coasts, Illinois, Louisiana and Texas. At that point, according to a Russian document cited by the special counsel, Mr. Putin’s intentions for 2016 were already explicit: to “spread distrust toward the candidates and the political system in general.”

In the intervening two years, Mr. Putin’s ire at America only increased. He blamed the United States for pushing for a full investigation of illicit doping by Russian athletes, which would lead to mass suspensions of the country’s Olympic stars. And when the leaked Panama Papers were published in April 2016, revealing that a cellist who was Mr. Putin’s close friend had secret accounts that had handled $2 billion, he charged that it was a smear operation by the United States.

“Who is behind these provocations?” he asked. “We know that among them are employees of official American institutions.”

Then something unexpected happened. Of the more than 20 major-party candidates running for the American presidency, only Mr. Trump had repeatedly expressed admiration for Mr. Putin as a “strong” leader and brushed off criticism of Russia. Only he had little interest in the traditional American preoccupation with democracy and human rights. Only he had explored business interests in Russia for years, repeatedly pursuing a Trump Tower project in Moscow and bringing his beauty pageant there in 2013.

“Do you think Putin will be going to The Miss Universe Pageant in November in Moscow,” the future candidate tweeted at the time, adding wistfully, “if so, will he become my new best friend?”

If Mr. Putin had been designing his ideal leader for the United States, he could hardly have done better than Donald Trump.

For some years, Mr. Trump had attracted attention from Russian conservatives with Kremlin ties. A Putin ally named Konstantin Rykov had begun promoting Mr. Trump as a future president in 2012 and created a Russian-language website three years later to support his candidacy. A Russian think tank, Katehon, had begun running analyses pushing Mr. Trump.

Mr. Trump as a candidate was “tough, rough, says what he thinks, rude, emotional and, apparently, candid,” wrote Alexander Dugin, an ultranationalist philosopher considered a major influence on Mr. Putin, in February 2016. Mr. Dugin declared that Mr. Trump probably had “no chance of winning” against the “quite annoying” Mrs. Clinton, but added a postscript: “We want to put trust in Donald Trump. Vote for Trump, and see what will happen.”

Against all expectations, Republicans across the country began to do just that, and soon Mr. Trump was beating the crowd of mainstream Republicans. Mr. Putin, said Yuval Weber, a Russia scholar, “found for the first time since the collapse of the U.S.S.R. that he has a prospective president of the United States who fundamentally views international issues from the Russian point of view.”

Asked about the surging Mr. Trump in December 2015, Mr. Putin said he