Russian President Vladimir Putin's sudden move to withdraw Russian forces from Syria, and declare the putative end of his country's main military operations there, once more caught many international observers by surprise. As my colleagues report, the pullout coincides with renewed diplomatic efforts to stop the ghastly five-year conflict and places the onus on the Kremlin-backed regime of Syrian President Bashar al-Assad to reach a deal with its opponents.

It also raises more questions about the approach taken by the White House, which had earlier warned that Moscow would get embroiled in a "quagmire," only to see pro-Assad forces make considerable gains at the expense of rebel militias backed by the United States and its allies.

There's no question that Russia's intervention in Syria had real game-changing effects. Initially premised on aiding the fight against the jihadist Islamic State, Putin's ensuing campaign has instead targeted mostly other rebel groups, including some factions supported by the CIA.

Russian President Vladimir Putin announced Russia will begin pulling most of its military from Syria. (The Washington Post)

Half a year ago, the Assad regime appeared on the verge of collapse. But months of Russian airstrikes turned the tide, allowing government troops and affiliated militias to recapture some 4,000 square miles of territory, almost encircle the war-ravaged city of Aleppo, and cut off vital rebel supply routes from Turkey. The Russian bombardments also enabled Syrian Kurdish militias to overrun rebel positions along the Turkish border, events which have sent geopolitical tremors across the region.

Those battlefield victories set the tone for subsequent U.N.-brokered talks in Geneva, as well as the conditions of a tentative cease-fire in Syria that were agreed upon last month by the United States and Russia. It led to admissions from senior U.S. officials that the Russians had "changed the calculus" of the conflict.

"One can doubt that Russia reached all of its goals, but it is difficult to dispute that the Russian operation provided the circumstances for the current ceasefire," writes Nikolay Pakhomov, a political analyst at the Russian International Affairs Council, which is based in New York City. "The clarity of Moscow’s moves, whether one can agree with them or not, has accelerated Russian interactions, if not cooperation, with the countries in the Middle East. Major regional actors are aware of Russian motives, interests, capabilities and goals and they can act accordingly."

That clarity, as Pakhomov put it, stands in contrast to the perceived waffling of the Obama administration, which had long called for Assad's departure but didn't follow through with decisive action, particularly when it deemed the regime's use of chemical weapons a "red line." In Iraq and Syria, the United States launched a concerted military campaign against the Islamic State, but has tried its best not to get too deeply entangled in the Syrian war on behalf of Assad's opposition.

This has frustrated Washington's traditional allies in the region and led to a jumbled strategy, perhaps most farcically illustrated last month when two Syrian factions that were both considered U.S. proxies ended up fighting each other.

"America’s regional friends are acting to defend their own interests, not always in ways congruent with American interests," writes Tamara Cofman Wittes of the Brookings Institution. "Obama’s apparent inability to see the conflicts between his Syria policy and his ISIS policy, and his reticence to do the sustained work necessary to hash out common priorities with the Gulf Arabs, Turkey, and Israel, have generated a problem more costly and harder to solve" than some of the uncertainties of intervention the White House fears.

"Obama has bet, and seems prepared to continue betting, that the price of direct U.S. action would be higher than the price of inaction," wrote the Atlantic's Jeffrey Goldberg in a lengthy piece on Obama's foreign policy published last week. "And he is sanguine enough to live with the perilous ambiguities of his decisions."

When it comes to Moscow's muscular actions abroad, Obama has cast these moves -- be they in Ukraine or Syria -- as the gambit of a diminished power groping for legitimacy at home and respect on the international stage. Here's what Obama said about Putin in an interview with Goldberg:

[Putin is] constantly interested in being seen as our peer and as working with us, because he’s not completely stupid. He understands that Russia’s overall position in the world is significantly diminished. And the fact that he invades Crimea or is trying to prop up Assad doesn’t suddenly make him a player. You don’t see him in any of these meetings out here helping to shape the agenda. For that matter, there’s not a G20 meeting where the Russians set the agenda around any of the issues that are important.

Putin's foray into Syria reasserted Russia's role in the Middle East. But the pullout tells its own story. It suggests that Moscow wasn't keen on a long-term investment in a Middle Eastern war. And it also shows that Russian backing of the Assad regime has its limits.

Here's a bit of historical context that explains why Russia is fighting to prop up its closest ally in the Middle East. (Ishaan Tharoor and Jason Aldag/The Washington Post)

"Even with Russian support, a complete nationwide military victory for Assad remains unlikely. Putin may now have concluded that a peace deal on Assad's terms is also beyond reach," writes Aron Lund of the Carnegie Endowment for International Peace, referring to the swaggering rhetoric coming out of Damascus in recent months.

"Assad's people were very confident only a week ago that Russia was going to take them all the way, help them reconquer all of Syria," Syria expert Joshua Landis told NPR. "In a sense, Russia's saying, we don't have to do that; we're not necessarily going to do that."

The hope is that this move adds much-needed impetus to ongoing U.N.-mediated talks.

"The timing of [Moscow's] announcement, which coincides with the start of the Geneva talks, is a clear signal to Assad that he better enter the negotiations in good faith," Randa Slim of the Middle East Institute told Politico. "This decision is the result of a growing Russian exasperation with Assad. Putin has just equalized the power relations inside Geneva's negotiating room."

That's not a bad outcome for the White House, which has been lukewarm about the prospect of Syrian regime change, despite issuing routine condemnations of Assad and his government's brutal assaults on its own people. The lessons of Libya and Iraq -- where the ousting of secular dictators boosted extremist elements and spawned greater chaos -- shadow all deliberations; so, too, does a recognition of the role that Assad's allies in Moscow and Tehran must play in reaching some settlement in Syria.

Perhaps the main political outcome of Putin's six-month Syrian campaign has been to draw the Kremlin closer to the White House, which has pinned its hopes for a Syrian solution on the Geneva process.

"The resurrection from oblivion of Russian-U.S. cooperation is one of the most important political results of the operation," wrote Vladimir Frolov, a Russian expert on international relations cited by the New York Times. "It turns out only two superpowers can stop the war."

Russia, of course, is not a real superpower. Hobbled by slumping oil prices and international sanctions, Russia's leaders are likely desperate to find some sort of new accommodation with the West.

"Putin might have played his cards right over the past six months, and his gamble could pay off diplomatically," writes Middle East pundit Marwan Bishara, "but it will be Obama who will eventually cash in his chips, whether through sanctions relief, diplomatic empowerment or even cooperation in other areas of the region and the world."

More on WorldViews