Alexei Navalny’s words that his prison sentence would mean life in his case unless there was political change in Russia have been borne out by his death as an inmate.
Mr Navalny was born in Butyn, about 25 miles outside Moscow.
He received a law degree from People’s Friendship University in 1998 and did a fellowship at Yale in 2010.
He gained attention by focusing on corruption in Russia’s murky mix of politicians and businesses; one of his early moves was to buy a stake in Russian oil and gas companies to become an activist shareholder and push for transparency.
By concentrating on corruption, Mr Navalny’s work had an appeal to Russians’ widespread sense of being cheated, and he carried stronger resonance than more abstract and philosophical concerns about democratic ideals and human rights.
He was convicted in 2013 of embezzlement on what he called a politically motivated prosecution and was sentenced to five years in prison, but the prosecutor’s office later surprisingly demanded his release pending appeal.
A higher court later gave him a suspended sentence.
The day before the sentence, Mr Navalny had registered as a candidate for Moscow mayor.
The opposition saw his release as the result of large protests in the capital of his sentence, but many observers attributed it to a desire by authorities to add a tinge of legitimacy to the mayoral election.
Mr Navalny finished second, an impressive performance against the incumbent who had the backing of Vladimir Putin’s political machine and was popular for improving the capital’s infrastructure and aesthetics.
Mr Navalny’s popularity increased after the leading charismatic politician, Boris Nemtsov, was shot and killed in 2015 on a bridge near the Kremlin.
Whenever Mr Putin spoke about Mr Navalny, he made it a point to never mention the activist by name, referring to him as “that person” or similar wording, in an apparent effort to diminish his importance.
Even in opposition circles, Mr Navalny was often viewed as having an overly nationalist streak for supporting the rights of ethnic Russians, he supported the annexation of the Crimean Peninsula by Moscow in 2014 although most nations viewed it as illegal, but he was able to mostly override those reservations with the power of investigations conducted by his Fund for Fighting Corruption.
Although state-controlled TV channels ignored Mr Navalny, his investigations resonated with younger Russians via YouTube videos and posts on his website and social media accounts.
The strategy helped him reach into the hinterlands far from the political and cultural centres of Moscow and St Petersburg and establish a strong network of regional offices.
His work broadened from focusing on corruption to wholescale criticism of the political system under Mr Putin.
He was a central galvanising figure in protests of unprecedented size against dubious national election results and the exclusion of independent candidates.
Mr Navalny understood that he could get attention with a pithy phrase and potent image.
His description of Mr Putin’s power-base United Russia as “the party of crooks and thieves” gained instant popularity; a lengthy investigation into then-prime minister Dmitry Medvedev’s lavish country getaway boiled down to the complex’s well-appointed duck house.
Soon, comical yellow duck toys became a popular way to mock the premier.
In 2017, after an assailant threw green-hued disinfectant in his face, seriously damaging one of his eyes, Mr Navalny joked in a video blog that people were comparing him to the comic book character The Hulk.
Much worse was to come.
While serving a jail sentence in 2019 for involvement in an election protest, he was taken to the hospital with an illness that authorities said was an allergic reaction, but some doctors said it appeared to be poisoning.
A year later, on August 20 2020, he became severely ill on a flight to Moscow from the Siberian city of Tomsk.
The plane made an emergency landing in the city of Omsk, where he spent two days in a hospital while supporters begged doctors to allow him to be taken to Germany for treatment.
Once in Germany, doctors determined he had been poisoned with a strain of Novichok, similar to the nerve agent that nearly killed former Russian spy Sergei Skripal and his daughter in England in 2018 and resulted in the death of another woman.
Mr Navalny was in a medically induced coma for about two weeks.
His first communication while recovering showed his defiant wit — an Instagram post saying that breathing on one’s own is “a remarkable process that is underestimated by many.
“Strongly recommended.”
The Kremlin vehemently rejected it was behind the poisoning, but Mr Navalny challenged the denial with an audacious move, essentially a deadly serious prank phone call.
He released the recording of a call he said he made to an alleged member of a group of officers of the Federal Security Service, or FSB, who purportedly carried out the poisoning and then tried to cover it up.
The FSB dismissed the recording as fake.
Russian authorities then raised the stakes, announcing that during his time in Germany, Mr Navalny had violated the terms of a suspended sentence in one of his convictions and that he would be arrested if he returned home.
Remaining abroad was not in his nature.
Mr Navalny and his wife boarded a plane for Moscow on January 17 2021.
On arrival, he told waiting journalists that he was pleased to be back, walked to passport control and into custody.
In just over two weeks, he was tried, convicted and sentenced to 2½ years in prison.
The events sparked massive protests that reached to Russia’s farthest corners and saw more than 10,000 people detained by police.
As part of a massive crackdown against the opposition that followed, a Moscow court in 2021 outlawed Mr Navalny’s Foundation for Fighting Corruption and about 40 regional offices as extremist, a verdict that exposed members of his team to prosecution.
When Mr Putin sent troops to invade Ukraine on February 24 2022, Mr Navalny strongly condemned the war in social media posts from prison and during his court appearances.
Less than a month after the start of the war, he was sentenced to an additional nine-year term for embezzlement and contempt of court in a case he and his supporters rejected as fabricated.
The investigators immediately launched a new probe, and in August 2023 Mr Navalny was convicted on charges of extremism and sentenced to 19 years in prison.
After the verdict, Mr Navalny said he understood that he was “serving a life sentence, which is measured by the length of my life or the length of life of this regime”.
A documentary called Navalny about his story won an Academy Award for best documentary in March 2023.
Mr Navalny’s wife spoke at the award ceremony, saying: “My husband is in prison just for telling the truth.
“My husband is in prison just for defending democracy.
“Alexei, I am dreaming of the day you will be free and our country will be free.”
Besides his widow, Mr Navalny is survived by a son and a daughter.