MOSCOW - In a few breathtaking hours, onetime oil baron Mikhail Khodorkovsky went from being a prisoner locked away for a decade in the remote depths of northern Russia to being a free man in Berlin. As he sped between those extremes, questions trailed behind.

Most prominently: Why Russian President Vladimir Putin decided to pardon the man who was once Russia's richest and one of the few with both the boldness and resources to challenge him.

Putin said he decided to approve Khodorkovsky's pardon application and let him walk free on Friday for humanitarian reasons - his mother is seriously ill. The way he announced it, in a scrum of journalists after his annual marathon news conference less than 24 hours earlier, had an air of spur-of-the-moment.

But there appears to have been considerable calculation behind it, and analysts saw it as a show of power and arrogance by the man who has dominated Russian politics since the turn of the millennium.

In the first burst of surprise after the pardon was announced, many speculated that Putin wanted to soften Russia's baleful image in the countdown to the Winter Olympics, his signature project, which starts Feb. 7 in Sochi.

"Rubbish," wrote Lilia Shevtsova of the Carnegie Moscow think-tank. "Putin has been all along demonstrating all signs that he does not care any more what the world is thinking of him. He has been showing the opposite: that he views world leaders as pathetic weaklings who can be ignored."

Although Putin is hypersensitive to opposition and has launched a series of measures over the last year and a half that chill dissent, he appears to have calculated that 10 years as an inmate has tamed the 50-year-old Khodorkovsky.