Governor of Moscow Region Sergei Shoigu, second from left, greets acting Defense Minister Anatoly Serdyukov, second from right, before a session of the State Council’s Presidium at the Kremlin in Moscow Oct. 9. (Sergei Karpukhin/Reuters)

A burgeoning $100 million corruption scandal claimed Russia’s defense minister Tuesday, as President Vladimir Putin sent Anatoly Serdyukov packing. It appeared to be the first time a top government official here has been fired for graft since the era of Soviet leader Mikhail S. Gorbachev in the 1980s.

Putin’s decision to rid the government of Serdyukov, a longtime loyal functionary, rather than simply shift him to another job as he normally would, quickly launched several theories as to what was behind the move. One thing analysts agreed on was that corruption was the pretext and not the underlying reason for the firing.

“Corruption is a main instrument for solving all questions in Russia,” said Alexander Golts, a leading defense expert. “Of course there was corruption, but that was not what was behind this.”

The criminal investigation involves the sale of defense ministry property at rock-bottom prices by an agency called Oboronservis. The head of that agency, a key figure in the probe, was reported Tuesday by the Interfax news agency to have possibly fled the country.

Serdyukov will be replaced by Sergei Shoigu, one of the most popular leaders in Russia. After more than a decade as head of the ministry for emergency situations (Russia’s equivalent of FEMA), Shoigu has for the past six months been governor of the region surrounding Moscow.

Serdyukov, 50 and the onetime head of Russia’s tax service, has been carrying out a thorough reshaping of Russia’s defense forces since his appointment in 2007. He was extremely unpopular among senior officers for his cuts and his open disdain for them. Perhaps more damaging, he also is estranged from his wife, who is the daughter of Viktor Zubkov, the chairman of energy company Gazprom and one of Putin’s most trusted senior colleagues.

Igor Bunin, president of the Center for Political Technologies here, said Tuesday that Serdyukov had outlasted his usefulness and that Putin was casting him aside in a bid to regain his own standing with the military. Putin also had to demonstrate decisiveness, Bunin said, to counteract recent rumors about his health.

But Golts argued that Putin, who had met with Serdyukov last week after the scandal broke, appears to have been forced into making the move. It was, he said, due to “the intrigue” of some unknown high official. And it makes Putin look weak. “It looks like he cannot control his guys,” Golts said.

A supporter of military reform, Golts argued that Serdyukov’s enemies in the ministry would use his downfall to discredit everything that he was trying to do.