MOSCOW — A screeching power tool sliced through Alexei Navalny's office door on Dec. 26, and a burly, masked Special Operations forces officer burst in, followed by another, and another — at least 20 in all. Within a minute, they dragged the Russian opposition leader out as he vainly grabbed for the door frame.

Instead of being cowed, Navalny set this terrifying show of Russian state force to a comical piano track in a March video in which he accused authorities of emptying his family’s bank accounts and sought crowdfunding for his Anti-Corruption Foundation.

Alexei Navalny / Youtube

Navalny, 44, was poisoned last month in Russia with a banned chemical weapon in the same group as the Soviet-era nerve agent Novichok, according to a German military laboratory. Such an agent is available only to state forces, according to analysts. U.S. Secretary of State Mike Pompeo said Wednesday there was a “substantial chance” the attack was carried out by senior Russian officials.

Russia vehemently denies that Navalny was poisoned, and Kremlin spokesman Dmitry Peskov referred to him Friday as “a person who became comatose as a result of causes that have not been determined.”

On Monday, German hospital officials said Navalny’s condition was improving after he was brought out of a medically induced coma.

A decade ago, Navalny was like an annoying gnat buzzing at Russian President Vladimir Putin. Then he was more like a terrier that wouldn’t stop barking. Now, he must appear to the president as a young lion ready to battle him for his turf.

Yet Putin and Peskov never acknowledge the opposition leader as a rival or even mention his name.

The Kremlin’s actions tell the real story, however. Navalny is enemy No. 1, always under surveillance, even on family vacations. Over the years, officials dipped into their authoritarian toolbox to stop him: digging up dirt, manufacturing charges, jailing him, fining him, draining his family’s accounts and harassing him with constant searches and seizures.

Nothing worked. In jail, he just read books and chatted to other inmates, including convicted murderers, he told one interviewer.

“They tried to pressure him with all possible means,” said Lyubov Sobol, a prominent member of his team who has faced similar pressure in her 10 years working alongside Navalny. “But he’s fearless. You cannot buy him. You cannot bribe him. He’s also dangerous because you can’t get compromising materials on him because he was never involved in corrupt deals or illegal activity. He’s not interested in leaving Russia.”

The Kremlin is trying to portray him as a politically marginal figure, Sobol said: “That’s why neither Putin nor Peskov ever use Navalny’s name.”

But his poisoning revealed just how significant a rival he is to Putin, analysts say.

“It was really a big, solid red line that Putin’s regime has crossed, trying to kill him,” said Andrei Kolesnikov, a Russia analyst with the Carnegie Moscow Center. “They are trying to demonstrate this figure is not serious. They themselves indicated who is the main enemy, the most serious enemy.”

Since Navalny was stricken on a flight to Moscow from the Siberian city of Tomsk on Aug. 20, Russia has released a tornado of bellicose propaganda designed to sow doubts about what happened to him. Russian doctors say he was not poisoned. Russian diplomats darkly warn of foreign foul play and accuse Berlin of having a “dirty political agenda.” Russian media never refer to Navalny’s poisoning, but to “the situation with Navalny.”

Recent constitutional changes cleared the path for Putin to try to stay in power until 2036, but neighboring Belarus has demonstrated the limitations of this strategy. The country’s longtime authoritarian leader, Alexander Lukashenko, is facing mass protests after a widely rejected election.

“The Russian leadership realized that a strong dictatorship can be ruined within one or two months,” said Russian opposition figure Dmitry Gudkov, likening Putin’s situation to Lukashenko’s. “Putin has been 20 years in power, and people are tired of him.”

Barred from state TV, Navalny countered with two YouTube channels that draw 15 million views a month. He airs videos exposing Russian politicians’ palatial mansions, fleets of luxury cars, yachts, horses and ponds filled with ducks or geese — all with a dose of edgy Russian humor.

He takes direct aim at the long-held Russian notion that massive corruption is intrinsic to the “Russian mentality.”

“Alexei challenges that very dangerous idea that it’s somehow inevitable for Russia to be corrupt,” said Matthew Murray, an expert on Russian corruption at Columbia University’s School of International and Public Affairs who met Navalny in 2007 in Russia. “And who benefits from that idea? It’s the current president of Russia, Vladimir Putin, and the people around him who have perpetrated this myth that Russians are dishonest and therefore we just reflect your basic legacy.”

When Navalny began to investigate Putin’s prized vanity project, the 2014 Sochi Winter Olympics, he was breezily optimistic about proving corruption: “It’s a 15-minute Google search,” he told his team.

The amount of graft proved so staggering that the exposé took a month to complete. Its airing caused Putin considerable embarrassment abroad.

“He is a person with a huge will. He has so many plans that at first seem impossible,” Sobol said of Navalny. “But he’s always right, and we manage to get the investigation done.”

Navalny told one interviewer that despite years exposing gross corruption, “it still makes me genuinely furious every time.” As well as open-source property registers, the team combs social media to snare boastful photos of yachts, luxurious vacation destinations and country houses.

Navalny obtained a law degree and in the 2000s began investigating corruption in the huge state oil and gas companies, filing lawsuits and blogging about his efforts. In 2011, he emerged as a leader in mass protests against election fraud.

Vladimir Ashurkov, a banker with the Alfa Group investment consortium, took notice.

“What attracted me to him was that many people were talking about corruption and he was doing something tangible,” he said. “He’s charismatic. He’s smart. He has an acute political sense. He was able to build an organization of like-minded people. Another layer is his bravery and resolve to continue what he’s doing even under pressure against himself and his family and against his organization. These are the ingredients that make him quite unique in Russia.”

Ashurkov became executive director of Navalny’s Anti-Corruption Foundation, which was set up in 2011, and fled Russia in 2014 following embezzlement charges he says were trumped up. Navalny announced in July that the foundation would have to be dissolved because of debts due to what he called spurious libel cases, but vowed it would be immediately relaunched.

Once Navalny emerged as a major threat, he faced similar charges. He was sentenced to five years in prison for embezzlement in 2013 but was freed after mass protests. In 2014, he and his brother Oleg were convicted in another embezzlement case and sentenced to 3½ years in prison. Alexei’s sentence was suspended, but Oleg served the full term, much of it in solitary confinement. Alexei Navalny saw it as psychological pressure designed to stop him.

In 2013, Navalny shocked the Kremlin by finishing second in Moscow’s mayoral elections with 27 percent of the vote.

“He was doing what people in developed democracies were doing, which was a novelty in Russia,” Ashurkov said. Navalny’s mayoral campaign, with three to four daily rallies, was “something that no candidate in Russia has ever done.”

Russian authorities miscalculated in letting Navalny participate, Kolesnikov said: “They thought that he would get two, three or five percent and it would show his weakness” and his strong showing “gave the authorities a fright and they decided not to let him participate in any election after that.”

A famous Navalny video from 2017 alleging that Russian Prime Minister Dmitry Medvedev had amassed property worth $1.4 billion was a critical turning point that hammered home the extent of governmental corruption. It gained 36 million views. But Navalny was barred from running against Putin in the 2018 presidential elections.

The only way to remove the regime, he argues, is through mass protests. Last year, he also launched “Smart Voting,” an app that directs voters to the candidates most likely to defeat Putin’s United Russia party — for example, in regional elections being held Sunday.

Navalny’s future is unclear, given the uncertainty about the long-term health effects of his poisoning. But the attack has already magnified his influence.

“After the poisoning, he simply became a more and more recognizable figure in Russia and a more and more important figure for the West, and especially for the European Union,” Kolesnikov said. “He is at the center of the historical process.”

In 2017, Navalny told an interviewer he was always aware of the dangers he faced and of the sacrifices of others, including his brother Oleg and opposition leader Boris Nemtsov, who was assassinated in 2015 near the Kremlin.

“If I stop, it will mean that all those sacrifices are useless, and they are not,” he said. “I do believe that my alternative is better for Russia.”