Six months after intervening strongly on the side of the regime of Bashar Assad, while claiming to be fighting ISIS, Russian President Vladimir Putin has ordered the beginning of the withdrawal of Russian forces from Syria:

MOSCOW — President Vladimir V. Putin of Russia on Monday ordered the withdrawal of the “main part” of Russian forces in Syria, a surprise move that he said was justified by the “overall completion” of Moscow’s military mission in the war-ravaged country.

Mr. Putin’s order, reported by the state news media, came as the war in Syria was about to enter its sixth year and a United Nations mediator in Geneva was trying to revive peace talks to stop the conflict, which has displaced millions and created a humanitarian catastrophe.

Russia has operated a naval base on the Syrian coast since the Soviet period, but Mr. Putin’s order seemed to relate to warplanes operating from a new air base in Latakia that since September have carried out intensive bombings against rebels fighting to topple President Bashar al-Assad of Syria.

Mr. Putin said the withdrawal would not mean the closing of the Latakia base, and he gave no indication when the withdrawal would be concluded.

Since Russian warplanes began their campaign on Sept. 30, Mr. Assad has gained ground against rebel forces and headed off the risk that his regime, Russia’s closest ally in the Middle East, might collapse.

“I believe, that the tasks put before the defense ministry have been completed over all,” Mr. Putin told Defense Minister Sergei K. Shoigu and Foreign Minister Sergey V. Lavrov at a meeting in the Kremlin on Monday evening. “Because of this, I have ordered that from tomorrow the main part of our military groups will begin their withdrawal from the Syrian Arab Republic.”

The Kremlin said Mr. Putin had telephoned the Syrian president to inform him of the Russian withdrawal, but gave no details of Mr. Assad’s reaction to the move, saying only that he had expressed thanks for Russia’s help and had praised the “professionalism and heroism” of Russian servicemen.

“The leaders noted that the actions of the Russian air forces have allowed a significant turn in the fight against terrorists,” a statement on the Kremlin website said.

In tandem with the military withdrawal, Mr. Putin called on Russian diplomats to strengthen their efforts in reaching a negotiated settlement.

“I am asking the Foreign Ministry to intensify the participation of the Russian Federation in the organization of the peace process on the settlement of the Syrian problem,” he said at the meeting.

Although the timing of Mr. Putin’s announcement was a surprise, some analysts had been expecting it, suggesting that Russia had accomplished what it wanted in Syria and that prolonging the deployment might lead to unanticipated problems.

At the same time, Mr. Assad and his aides have shown increased unwillingness to negotiate a political settlement, which may have irked his Russian allies.

“Over the past few weeks, the Assad regime has made a number of statements indicating their negotiating position with the opposition remains quite rigid,” said Andrew J. Tabler, a scholar of Arab politics at the Washington Institute for Near East Policy. “Putin’s announcement, coming on the same day U.N. peace talks started in Geneva and in the absence of a decisive victory by Assad’s forces, indicates that Moscow might not be with Assad till the bitter end,” Mr. Tabler said.

Russia’s military intervention in Syria, which involved the deployment of 45 strategic and tactical bombers as well as fighter planes, helicopters and antiaircraft systems, was Moscow’s first such action outside the former Soviet Union since the collapse of communism in 1991.

The state-controlled news media in Russia trumpeted the intervention as a sign that Moscow had regained its role as a global military power. Television news broadcasters, after weeks of hailing the operation daily, seemed stunned Monday evening when news of the withdrawal first broke.

Russian warplanes gave a major boost to Mr. Assad’s fading military fortunes, flying more than 9,000 sorties and helping the Syrian government regain control of 400 settlements, according to Mr. Shoigu, the Russian defense minister.

The decision to withdraw, announced as abruptly as Russia’s initial decision to intervene, could allow Mr. Putin to avoid the risk that what has been a relatively painless and, in both military and public relations terms, highly successful mission for Russia could turn into a quagmire costly in lives, money and political capital for the Kremlin.

One interpretation of Russia’s decision, of course, is that Putin may be choosing to distance Russian policy in Syria from the Assad regime to some degree, perhaps as a prelude to taking on a greater role in the ongoing peace negotiations. Until now, the United States and Russia have largely been at odds over how to proceed when it comes to a peaceful resolution of the conflict in Syria. The United States, and much of the West for that matter, has taken the position that there can be no resolution regarding the civil war that is now entering its sixth year as long as Bashar Assad and his cohorts remain in power. Toward that end, American policy has always had the dual goals of both seeking to end the Assad regime’s control of the Syrian government and stopping the spread, and reversing, the spread of ISIS influence in the region. Given the fact that removing Assad from power would only seem to make it more likely that ISIS will not only expand but thrive from the ensuing chaos, this strategy has never made much sense. For the Russians, on the other hand, the goal has always been to maintain the Assad regime in power, largely due to the long-standing relationship between that regime and both the Soviet Union and, since 1991, Russia. It is, after all, because of the Assad regime that Russia has its only military outpost with a warm water port outside Russia itself. At the same time, there have been some hints that Russia might be willing to consider a peace plan that includes an eventual end to the Assad regime. From that point point of view, this announcement could mark the beginning of a change of policy by Moscow that could have a big impact on the efforts to resolve the ongoing civil war.

The more likely explanation, of course, is that there will be no change in policy by Russia at all, and that the peace talks will continue to go nowhere. Instead, the reason Russia is beginning to scale back its intervention in Syria is because it has largely achieved its goals of degrading the anti-Assad forces that were the greatest threat to the Damascus regime, and that the remaining tasks will be left to Assad’s forces to finish. In this regard, it’s worth remembering that the vast majority of Russia’s air strikes have been against rebel groups that the West does not believe are part of ISIS or any other jihadist group, and that these groups were targeted precisely because of the fact that they were the greatest threat to the Assad regime. Withdrawal at this point could easily be a signal from Russia that they have accomplished as much as their air power can accomplish, that the strongest anti-Assad forces have indeed suffered serious losses as many reports have indicated, and that the goal of ensuring the survival of the Assad regime has succeeded as much as possible. In this case, it’s unlikely that we’ll see much progress at all from the peace talks unless the West accepts the idea that Assad may be here to stay at least for a little while longer. Which ever it is, one assumes there’s some logic to Putin’s move here that we’ll discover in due course.