Paul Pillar describes Russia's current stalemate situation in Syria and why he thinks the Russian leadership considers it acceptable for the time being (Syria: Still a No-Win Situation The National Interest 06/05/2017):
The interests of the Syrian regime’s most important ally—Russia—are a key determinant of this stalemate. Russia has succeeded, at a cost acceptable to it, in achieving its objectives of shoring up its only client regime in the Middle East, securing its modest naval and air presence in the country, and demonstrating that it still is a player to be reckoned with in that part of the world. Moscow has an interest in not having those accomplishments erased. To try to do more than that, with a sweeping rollback of remaining opposition positions in Syria, would start to entail unacceptable costs to the Russians. Attempting to own all of Syria, à la Afghanistan in the 1980s, is not in Russia’s interest.
Pillar is not suggested that the US should meddle more in Syria to tweak the Russians. We tried that in Afghanistan in the 1980, when we backed the brave, fiercely independent mujaheddin fighters. Well, that's what we called them then. We usually call them Muslim terrorists now. Pillar writes:
The makers of U.S. policy should bear in mind how little stake the United States has in specific outcomes in Syria, beyond the concern with exportable extremism and political violence (and they should remember that even ISIS was exported from Iraq, where it was born under a different name as a consequence of the U.S. invasion and occupation). Avoidance of situations that risk sucking the United States into a larger military clash will be important. A sample of the risks of such escalation recently occurred when U.S. forces attacked a pro-regime militia, said to be supported by Iran, when it got what the U.S. military regarded as uncomfortably close to an installation that U.S. forces use in southern Syria. [my emphasis]He concludes with a pragmatic suggestion, which the Trump Family Business Administration will likely ignore, "Meanwhile the Trump administration needs to discard its penchant for regarding every outcome in terms of wins and losses. So regarded, when you have a no-win situation such as Syria, that means the only possible outcome is a loss. And even when parties we don’t like suffer a loss, that does not necessarily help U.S. interests."
Ueber-Realist Stephen Walt also has some current advice for US policy in the Middle East. Walt is a fan of "offshore balancing" in foreign policy. Here's how he recommends the US apply it in the Middle East (Making the Middle East Worse, Trump Style Foreign Policy 06/09/2017):
There is no potential hegemon in the Middle East today, and as yet no external “peer competitor” like the former Soviet Union who might conceivably dominate the region. There is therefore no need for the United States to double down on its present commitments to any Middle Eastern countries. None of America’s current partners deserve unconditional support on either strategic or moral grounds: 1) Egypt is a brutal military dictatorship with a failing economy and of modest strategic value; 2) Saudi Arabia is a fundamentalist theocracy, is helping destroy Yemen and Syria, and engaged on a massive economic reform project that may fail catastrophically; 3) Israel is marching rightward toward full-fledged apartheid; and 4) Turkey is a mockery of democracy that has gone from “zero problems with neighbors” to problems with nearly all of them. Trump is easily seduced by foreigners who cater to his vanity — as his Saudi hosts clearly realized — but stroking the president’s ego is not the same as contributing to the U.S. national interest.
Facing an environment like this, a smart superpower would hedge. Instead of trying to create some sort of Sunni axis, the United States should return to the underlying logic of its earlier approach.The core U.S. interest in the Middle East, as in other vital areas, is to preserve a rough balance of power and prevent any single state (or external great power) from dominating. The Middle East is as divided today as it has ever been, which means the core U.S. objective is easy to achieve. Accordingly, the United States should be reaching out to countries like Iran, instead of jumping deeper into bed with Tel Aviv, Cairo, Riyadh, and Ankara. As the director of the CIA’s political Islam strategic analysis program, Emile Nakhleh, recently wrote, “Taking sides in the perennial sectarian feud between Sunni and Shia Islam or between Saudi Arabia and Iran is, in the long run, inimical to American national security and interests in the Islamic world.”