FILE - In this Monday, Dec. 27, 2010 file photo former oil tycoon Mikhail Khodorkovsky stands behind glass at a court room in Moscow, Russia. FILE In this Friday, July 4, 2003 file photo Mikhail Khodorkovsky, then chief executive of Russia's Yukos oil company and Russia's richest man according to Forbes magazine, speaks to press outside the General Prosecutor's Office, where he spent just under two hours being questioned in Moscow, Russia. Russian President Vladimir Putin said on Thursday Dec. 19, 2013 that he will pardon his arch-enemy Khodorkovsky who has spent the past 10 years in prison on tax evasion and embezzlement charges. AP Photo/ Ivan Sekretarev MOSCOW (AP) - Russian President Vladimir Putin signed a decree Friday to pardon jailed tycoon Mikhail Khodorkovsky. Here's a look at Khodorkovsky, the implications of his imprisonment and his impending release: At the time of his arrest in October 2003, when special forces stormed his private jet at a Siberian airport, Khodorkovsky was the head of Russia's largest oil producer. He was believed to be the country's richest man, with a fortune estimated at $15 billion. He was also a constant thorn in Putin's side. Putin had set out to tame the "oligarchs," the hugely wealthy businessmen who wielded strong political power. He made it clear they could keep their wealth if they agreed to stay out of politics. Most complied, but Khodorkovsky didn't. He funded opposition parties in parliament, which still had the power to block Kremlin legislation. He also supported independent media as the Kremlin was taking over the last national television network outside its control. Khodorkovsky was convicted of tax evasion and sentenced to nine years in prison in May 2005. His Yukos oil company was effectively crushed under the weight of a $28 billion back-tax bill. The court also ruled that Khodorkovsky and partner Platon Lebedev had to pay $600 million in back taxes. Yukos was sold off, mostly to state oil company Rosneft, allowing the Kremlin to reassert control of the country's oil business as well as stifle an inconvenient voice. In 2011, Khodorkovsky was convicted again, this time on charges of stealing the oil that his company produced and reselling it abroad at higher prices. He was due to be released from prison in August 2014. Many trial witnesses said the charges were bogus, even absurd. Critics saw both trials as a nakedly political move to eliminate Putin's biggest rival. Before his arrest, Khodorkovsky was not a sympathetic figure to most Russians, who resented how the oligarchs had enriched themselves in the post-Soviet privatization era, when state assets were sold in murky deals for shockingly low amounts. Although he was admired for making Yukos the first major Russian company with Western-style bookkeeping, he was also said to be a ruthless boss. But behind bars, the tycoon swiftly turned into an articulate political thinker and a much sought-after columnist. He wrote for leading Russian media and corresponded with prominent Russian authors. Khodorkovsky's prison writing has showed the evolution of his political views. In 2005, he penned a column headlined "The Left Turn" where he virtually repented for the sins of privatization and called on Russian authorities to come up with a leftist, more socially oriented agenda. He also proposed that oligarchs pay a tax for the companies they had bought up. In an October opinion piece for The New York Times, Khodorkovsky said Putin was the main reason that Russia's economy was stagnating and its social fabric deteriorating. "Today the system for running the country is called "Vladimir V. Putin." Can he change? I don't want to give a categorical answer: A human being is too complicated a creature for that," he wrote. As a tycoon, Khodorkovsky avoided the ostentation of his other oligarchs. In prison, he became downright frugal. Igor Gnezdilov, Khodorkovsky's Siberian prison cellmate in 2007, told the Kommersant newspaper how he once chided Khodorkovsky for wearing a cheap track suit. Gnezdilov suggested that the former oligarch get himself "decent" clothes. Why would I? Khodorkovsky replied, according to Gnezdilov. Reflecting how public perception of him has changed, a poll by the Levada Center published in June showed that 33 percent of Russians would favor his early release as opposed to 19 percent in 2007. A mere 16 percent said they would oppose his release, compared to 44 percent six years ago. With the 2014 Winter Olympics in Sochi just 50 days away, the Kremlin has been anxious to soothe Western criticism of its human rights record. The Russian parliament on Wednesday passed an amnesty law that would drop charges against thousands of Russians and release thousands more. Under the amnesty bill, Greenpeace activists arrested in the Arctic are likely to be allowed to go home and jailed members of the punk band Pussy Riot be released. Khodorkovsky would have remained the most prominent politically tainted prisoner. Chris Weafer, a senior partner at Moscow's Macro Advisory consulting firm, said it appears that Russia is getting sensitive to improving its image as Sochi approaches and "is on a campaign to kind of defuse the long-time issues." The political weight he has acquired over the past decade would make him an attractive figure for Russia's nascent opposition. But he may not have the stomach for Russian politics after a decade in the country's notoriously harsh prisons. The toll it took on him was clear in an interview earlier this year. Khodorkovsky was asked what he would have done if he had known before his arrest that he would be spending the next 10 years in prison. "I'm afraid I would have shot myself," he answered. Associated Press writers Jim Heintz and Laura Mills contributed to this report from Moscow.