Alexei Navalny, 44, is Russia’s best-known opposition leader. He was brought out of an induced coma, doctors in Germany said Monday, after falling ill on a flight from Siberia to Moscow on Aug. 20. After a standoff with Russian doctors, he was evacuated to Berlin for medical treatment.

German doctors said studies showed he had been poisoned, probably with a nerve agent. The Kremlin dismissed those findings and said that it hoped the incident would not damage relations between Moscow and the West, Reuters reported. Russian prosecutors said that they would not launch a criminal investigation into the alleged poisoning. Doctors cautioned Monday that the long-term impacts of the poisoning on his Navalny’s health were still unclear.

In a country where one man — Russian President Vladimir Putin — has dominated political life for more than two decades, Navalny has been a persistent, influential and sometimes controversial figure in (and figurehead for) the repressed political opposition.

But his prominent position and anti-Kremlin politics came with huge risks. He and other members of his family have faced legal attacks, and he has been hospitalized after a number of alleged attacks.

Who is Navalny?

Navalny was born June 4, 1976, in Obninsk, a city roughly 60 miles southwest of Moscow. His father was born in Ukraine, and he spent summers in Chernobyl before the nuclear accident in 1986.

After earning degrees in law and finance from Russian universities, Navalny entered politics in 1999, just as Putin first took up national leadership. Navalny joined the liberal opposition party Yabloko and pushed it toward a more nationalist message that put him in conflict with party leadership.

How did he become Russia’s leading opposition figure?

Navalny was expelled from Yabloko in 2007, in part because of controversial comments on immigration and his decision to attend the annual Russian March, which is anti-Putin but includes members of the far right.

While running a small corporate law firm in Moscow, Navalny developed the strategy of buying stocks in state-linked oil companies and banks so that he could become a minority shareholder and question the companies’ leadership.

Navalny later formed a group known as the Anti-Corruption Foundation to expand this work and launch investigations that increasingly struck at the heart of the Kremlin elite. A 2017 exposé alleged that Prime Minister Dmitry Medvedev had a vast, $1 billion network of palaces. The YouTube video accompanying the investigation has received more than 35 million views.

As an activist, Navalny gained traction in part because of his personal charisma and pugnacious rhetoric. In a 2011 radio interview, he dubbed United Russia, the political party that backs Putin, the party of “crooks and thieves.” The condemnation soon caught on.

Has he run for elected office?

Navalny has become the country’s most prominent opposition leader, and he played a leadership role in several political movements. But he has faced numerous obstacles when running for elected office.

He was barred from running for president in the 2018 election, with the Central Election Commission arguing that his campaign was ineligible because of a conviction in a 2014 embezzlement case that his supporters viewed as political retribution.

When he has been allowed to run, there are indications of political support. In 2013, he won 27 percent of the vote against a key Kremlin ally in the Moscow mayoral election, a result that surprised some analysts, as Navalny did not have the backing of state media and was forced to travel away from Moscow during the campaign because of legal problems.

Election monitors consistently report violations during Russian elections that compromise their integrity.

Has he been targeted politically?

Navalny and his supporters point to numerous instances of harassment for his activism, including legal and physical threats.

In 2014, Navalny was sentenced to five years in prison for allegedly embezzling $500,000 worth of lumber from a state-owned company. The prison sentence was later suspended. Though the case was declared unfair by the European Court of Human Rights (ECHR) in 2016, a Russian court reaffirmed it the next year.

Further legal cases have kept Navalny in court or under house arrest. In late 2014, both Navalny and his brother Oleg Navalny were sentenced to prison time for allegedly embezzling funds from French cosmetics firm Yves Rocher.

Although Navalny’s sentence was suspended, and the ECHR again said the case was unfair, his brother spent three and a half years in prison before being released in 2018.

This year, Russian authorities seized Navalny’s bank accounts and those of his wife, son and daughter. After a lawsuit from Yevgeniy Prigozhin, an oligarch close to Putin and the target of an investigation, Navalny was forced to close his Anti-Corruption Foundation in July, but he pledged to continue its work under a different name.

Navalny has also faced physical harassment and threats. In 2017, he was doused with an antiseptic green dye several times. Although he made light of the incident, posing for photographs on his social media accounts, after one incident in April of that year he was hospitalized after the dye went into his eye.

In 2019, Navalny was hospitalized with an “acute allergic reaction” after again being detained. His personal physician said he may have been affected by an unknown chemical substance.

The Aug. 20 incident appears to be the most serious threat against his life yet. His spokeswoman, Kira Yarmysh, said he started to feel ill during a flight to Moscow from the Siberian city of Tomsk, leading the pilot to make an emergency landing in Omsk, where he was taken to a hospital and placed on a ventilator.

Yarmysh suggested that Navalny may have been poisoned after drinking a cup of tea at the airport. “This is Putin. Whether he personally gave the order or not, the blame is entirely with him,” she wrote on Twitter.

A Russian newspaper reported that Navalny had been under covert surveillance in Siberia, with undercover agents tracking who he met, where he stayed, even what he and his associates ate.

Navalny’s team had used tactics to throw off those following him, Moskovsky Komsomolets reported, including staying in safe houses and booking multiple rooms in hotels.

Have other opposition figures been targeted?

Throughout Putin’s long rule of Russia, political opponents have been jailed. For example, Mikhail Khodorkovsky, a Russian oligarch who was initially supportive of Putin, spent 10 years in prison after running afoul of the Kremlin.

Some have been killed. Boris Nemtsov, a liberal politician once seen as a potential successor to Putin’s predecessor, Boris Yeltsin, was gunned down just steps away from the Kremlin in 2015. The murder was shocking even by Russian standards. Putin suggested it was a contract killing designed to embarrass the Kremlin.

There have been several high-profile cases of poisonings or alleged poisonings. In 2006, Alexander Litvinenko, a former officer of the Russian Federal Security Service (FSB), died after being poisoned in London.

Litvinenko had written a book that alleged a deadly false-flag conspiracy to help Putin get elected in 1999. British authorities later said that he had been poisoned after drinking a cup of tea laced with polonium-210 and that Putin himself may have ordered the assassination.

Vladimir Vladimirovich Kara-Murza, an opposition activist who was viewed by some as Nemtsov’s protege, has fallen into sudden and unexplained comas twice in recent years. He has said he was likely poisoned for political reasons.

This report has been updated.