Libya is a particular grievance. Mr. Putin seethed over the aftermath of the United Nations resolution establishing what was supposed to be a no-fly zone in Libya, which China and Russia last March agreed not to veto. Many in the government contend that President Dmitri A. Medvedev was deceived by Western allies who then used the resolution to justify airstrikes to drive Col. Muammar el-Qaddafi from power.

“We were naïve and stupid,” said Mr. Satanovsky, an influential analyst. “The Chinese were the same. Trust this: That was the last mistake of such type.”

Another consideration is practical. Syria is a major customer of Russia’s state weapons exporters, who by one estimate have already lost as much as $10 billion in orders during the political turmoil of the Arab Spring and a missile contract with Iran that was shelved as a result of the “reset” with Washington. The military industry holds sway over a significant slice of Russian voters and “will be very angry at the ruling group” if further contracts are lost, said Fyodor Lukyanov, editor of Russia in Global Affairs.

“We have an election year here, and this time it is a more real election campaign. He is campaigning quite seriously,” Mr. Lukyanov said. “That means all groups of society are valuable, and the military industry is very angry over this chain of events.”

Russia has benefited from Syria’s isolation from the West over the years because it enjoys preferential access for its arms and petroleum industries. Syria places orders worth about $700 million a year, making it a “major, very important, high-priced client by Russian standards,” said Ruslan Aliyev, a defense specialist at the Center for Analysis of Strategies and Technologies, a Moscow research center. But Moscow wields little influence over Mr. Assad, he said.

This created problems for Moscow in 2006, when Israel, another Russian ally, found that Hezbollah fighters were using Russian-made weaponry that had been sold to Syria, in violation of Syria’s agreement with Russia. Mr. Aliyev called this “a weighty slap in the face.” Mr. Assad has also defied Russian counsel to “stop the hostilities and bloodshed.”

“It’s difficult to defend a person who does not want to cooperate with you and is not prepared to take advice from you,” Mr. Aliyev said.