Russian opposition leader Alexei Navalny has died on Friday at the Arctic prison colony where he was serving a 19-year sentence, Russia’s Federal Penitentiary Service said.

Navalny lost consciousness after a walk and could not be revived by paramedics, the correctional facility said.

Here are some of the most important events in his life:

August 20, 2020 – Navalny is hospitalized in the Siberian city of Omsk after falling ill and losing consciousness during a flight over Siberia. Navalny’s spokeswoman says he was poisoned, possibly from a cup of tea he drank before takeoff from Bogashevo airport in Tomsk, but Russian doctors treating him say they found “no trace” in his blood or urine .

August 22, 2020 – Navalny will be flown to the Charité hospital in the German capital Berlin for treatment. The Russian medical team treating him initially rejected the move before later releasing him. German doctors say their tests suggest Navalny was poisoned.

September 2, 2020 – German officials say there is “clear evidence” that Navalny was poisoned with the nerve agent Novichok, a Soviet-era chemical weapon. German Chancellor Angela Merkel described Navalny as a victim of attempted murder, adding that there were “serious questions that only the Russian government can and must answer.” International is calling for an investigation into the incident.

September 3, 2020 – The Kremlin rejects claims, including those from Navalny’s team, that Moscow was behind the poisoning.

September 4, 2020 – A Russian toxicologist says Navalny’s health may have deteriorated due to diet, stress or fatigue, stressing that no poison has been found in his body.

September 7, 2020 – German doctors say Navalny has woken up from an induced coma.

11th-13th September – Local elections are taking place in Russia, with Navalny’s allies winning in Siberian cities.

September 14, 2020 – Laboratories in France and Sweden confirm Germany’s findings that Navalny was poisoned with the nerve agent Novichok. French President Emmanuel Macron is urging Putin to shed light on the “attempted murder,” but the Russian leader is simply trying to condemn “baseless” accusations.

September 15, 2020 – Navalny posted a message on Instagram saying he could breathe without help. He appears with his wife Julia and his two children, sitting up in bed and emaciated.

September 17, 2020 – Navalny’s associates say they discovered traces of Novichok on a bottle that came from the hotel in Siberia where he stayed before his illness.

September 21, 2020 – Navalny says Western laboratories have found traces of Novichok in and on his body and that he is demanding that Moscow return his clothes from the day he fell ill.

September 22, 2020 – Navalny is released from hospital and doctors say a “full recovery is possible.” The Kremlin said Navalny was welcome to return to Moscow, while its spokeswoman said Russia had frozen his assets while he was in a coma.

October 1, 2020 – Navalny accuses Putin of being behind the poisoning and says he will not give the Russian president the pleasure of being in exile. Putin’s spokesman Dmitry Peskov accuses Navalny of working for the CIA and calls his claims “baseless and unacceptable.”

December 14, 2020 – Citing flight records and mobile phone geolocation data, investigative website Bellingcat and Russian media outlet The Insider publish results of a joint investigation into Navalny’s alleged poisoning. Working with Der Spiegel and CNN and with the support of Navalny, they claim to have identified a team of assassins from the Russian secret service FSB who have been tracking him for years. Intelligence officers and poison labs are named as being behind the operation.

December 21, 2020 – Navalny releases a recording in which he appears to trick an FSB agent into confessing that he tried to kill him by injecting poison into his underpants. The FSB calls the video clip of the phone call a “fake.”

December 28, 2020 – The Russian prison service gave Navalny a last-minute ultimatum, telling him to fly back from Germany immediately and report to a Moscow office the next morning. The prison service warns Navalny that he will be imprisoned if he returns after the deadline. Navalny’s spokeswoman says it is impossible for him to return in time, adding that he is still recovering from his poisoning and accusing the prison service of acting on Kremlin orders.

January 12, 2021 – Court documents show that a Russian judge was asked to jail Navalny in absentia because, among other things, he was said to have violated the terms of a suspended sentence he was serving.

January 13, 2021 – Navalny posted a video on Instagram in which he announced plans to return to Russia. “It was never a question of whether we should return or not. Simply because I never left. After I arrived in the intensive care unit, I ended up in Germany for one reason: they tried to kill me,” he says.

January 17, 2021 – Navalny flies from Germany to Russia. He was arrested shortly after landing at Moscow’s Sheremetyevo Airport. The arrest sparked condemnation from several European and international powers and loud calls for his immediate release.

January 18, 2021 – A Russian judge sentenced Navalny to 30 days in custody for violating the terms of his suspended sentence during a hastily arranged court hearing at a police station on the outskirts of Moscow. Navalny calls on Russians to take to the streets in protest after the decision. “Don’t be afraid, take to the streets. Don’t go out for me, go out for yourself and your future,” he said in a video posted on social media.

February 2, 2021 – A Moscow court sentenced Navalny to two and a half years in prison for violating his probation. In prison, Navalny goes on a three-week hunger strike to protest a lack of medical treatment and sleep deprivation.

June 9, 2021 – A Moscow court bans Navalny’s foundation for fighting corruption and about 40 regional offices as an extremist and closed his political network. Close associates and team members are being prosecuted and are leaving Russia under pressure. Navalny keeps in touch with his lawyers and team from prison, and they update his social media accounts.

February 24, 2022 – Russia invades Ukraine. Navalny condemns the war in social media posts from prison and in his court appearances.

March 22, 2022 – Navalny will be sentenced to another nine years in prison for embezzlement and contempt of court in a case his supporters dismissed as trumped up. He will be transferred to a maximum security prison in Russia’s western Vladimir region.

July 11, 2022 – Navalny’s team announces the relaunch of the Anti-Corruption Foundation as an international organization with an advisory board. Navalny continues to file lawsuits in prison and tries to form a union at the facility. In response, prison officials regularly place him in solitary confinement for alleged disciplinary infractions, such as not buttoning his garment properly or not washing his face at a certain time.

January 11, 2023 – Over 400 Russian doctors are signing an open letter to Putin calling for an end to so-called abuse of Navalny after reports he was denied basic medication after falling ill with the flu. His team expressed concern about his health, saying he had acute stomach pains in April and suspected he was slowly being poisoned.

March 12, 2023 – “Nawalny”, a film about the assassination attempt on the opposition leader, wins the Oscar for best documentary film.

April 26, 2023 – Speaking on video from prison during a hearing, Navalny said he was facing new extremism and terrorism charges that could keep him behind bars for the rest of his life. He adds sardonically that the accusations imply that “I am carrying out terrorist attacks while in prison.”

June 19, 2023 – The trial begins in a makeshift courtroom in Penal Colony No. 6, where Navalny is being held. Shortly after it began, the judge closed the trial to the public and media, despite Navalny’s demands that the trial be kept open.

July 20, 2023 – In their closing argument, the public prosecutor’s office demands that the court sentence Navalny to 20 years in prison, reports the politician’s team. Navalny said in a subsequent statement that he expected his sentence to be “huge… a Stalinist term,” referring to Soviet dictator Josef Stalin.

December 11, 2023 – Navalny’s whereabouts are unknown When officials at the penal colony where he is serving his sentence told one of his lawyers that he was no longer on the inmate list, his spokeswoman says.

December 15, 2023 – Allies of the imprisoned Navalny says his lawyer The court is told that the leader was moved from the penal colony east of Moscow where he is serving his time, but where he was taken is not told. The Kremlin says it has “no information.”

December 25, 2023 – Navalny’s aides say he was located in a prison colony above the Arctic Circle nearly three weeks after contact with him was lost.

December 26, 2023 – Navalny Publications a sardonic statement about his transfer to an Arctic prison colony nicknamed “Arctic Wolf”, his first appearance since his co-workers lost contact with him.

January 9, 2024 – Navalny says on social media that officials at the Arctic penal colony isolated him in a tiny punishment cell for a minor infraction.

January 10, 2024 – A smiling and joking Navalny appears in court via video feed from the Arctic penal colony, the first time the Russian opposition leader has been shown on camera since his transfer to the remote prison.

February 1, 2024 – In a social media statement, Navalny called on Russians to express their protest against President Vladimir Putin in next month’s presidential election by voting at a certain point on Election Day.

February 15, 2024 – Navalny was last seen in public when he appeared via video link at a court hearing. He jokingly asked the judge for a portion of this “huge salary.”

February 16, 2024 – Navalny has diedstate media reported, citing the region’s prison service.