Aaron David Miller is a vice president and distinguished scholar at the Woodrow Wilson International Center for Scholars and author of "The End of Greatness: Why America Can't Have (and Doesn't Want) Another Great President." Miller was a Middle East negotiator in Democratic and Republican administrations. Follow him @aarondmiller2. The opinions expressed in this commentary are his.

(CNN) The Syrian civil war is by no means over, but this year will bring a decisive turn in the conflict that may reduce the overall level of violence and fundamentally -- and perhaps for some time to come -- change the balance of power on the ground.

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Indeed, the Assad regime may not be able to reunite the country nor regain international legitimacy. But more than likely what was once unimaginable: Assad's outlasting of his domestic -- and international adversaries -- has now come to pass.

And in one of the cruelest ironies of all, 2017 will also demonstrate the overturning of all the Obama administration's assumptions about Syria and perhaps open the door for the Trump administration to take advantage of the new realities.

Indeed, in the cruel and unforgiving world of political transitions, one President's misfortune may well turn out to be another's opportunity.

Assad Must Go

Probably not. President Obama will be out of power long before Assad. That reflects the difference between a democracy and authoritarian polity; but it also reveals the perils of calling repeatedly for a dictator's demise -- as Obama did -- without the willingness or capacity to make it happen.

The fact is that Assad -- propped up by Russia and Iran -- will likely be staying, particularly in the wake of his crushing defeat of the opposition in Aleppo.

Indeed, Assad will be key part of a transition to the new Syria, whatever that means.

Now that his allies, Russia and Iran, are in charge of launching the political negotiations later this month in Kazakhstan, it's hard to imagine they'd easily abandon -- even as part of a long transition -- someone they fought so hard to preserve.

The Russians will get stuck in a quagmire

So argued and hoped the President and secretary of state. In fact, the Russian military intervention in September 2015 backed up by Iranian support on the ground turned the tide of the war in Assad's favor at minimum cost.

JUST WATCHED Russia slams US policy shift in Syria Replay More Videos ... MUST WATCH Russia slams US policy shift in Syria 01:50

Putin blocked US efforts to pressure Assad out, pushed Russia into the central role in any solution to the Syrian civil war and put himself in a position to use Syria as part of a bigger game to advance Russian interests with the administration.

Right now, Putin has no clear or easy exit out of Syria.

But it's not clear he wants or needs one yet. Fighting ISIS in Syria is still very much in Russia's interest and a way to dangle closer cooperation with a new Administration.

There's no military solution

This was a key administration talking point about Syria as it wrestled with a half dozen failed efforts to create a lasting ceasefire and political transition.

The analysis that there was no military solution to the conflict was partly right. It's unlikely that the Assad regime has the manpower, military muscle and the economic resources power to reimpose its control over a fractured Syria. But that doesn't mean that military power couldn't be deployed to ensure the survival of the regime and the crushing of the opposition as a mortal threat.

That's precisely what's happened. Backed by its allies, the regime has reasserted its control over what Syria watchers describe as essential Syria: the key cities of Damascus, Homs, Aleppo and the coast. This is more than an Alawi mini state; it may be sufficient to sustain the regime indefinitely and create a solution of sorts -- at least after six years of civil war. The opposition -- diffuse and decentralized -- will go to ground, revert to a nagging insurgency and retain some capacity to harass the regime. But they can no longer threaten. Indeed, if the mainstream opposition is forced closer to the jihadists in order to survive, their legitimacy will also be imperiled, particularly as the regime consolidates its control.

ISIS will be destroyed

JUST WATCHED Guehenno to Trump: You cannot 'just crush' ISIS Replay More Videos ... MUST WATCH Guehenno to Trump: You cannot 'just crush' ISIS 06:24

Not likely. Administration officials have repeatedly talked about destroying ISIS. Whether they actually believed they could eradicate ISIS and its ideology is doubtful. Offensives against Mosul in Iraq and eventually Raqqa in Syria will shrink the "Caliphate" and likely eliminate its leaders. Its proto state and control over people and resources will be diminished too. But ISIS, al Qaeda; and its affiliate Fatah al-Sham will not disappear.

As long as Assad remains and tensions between Shia and Sunnis persist, the jihadists will be able to play on Sunni grievances in Syria, conduct terror attacks in Syria and Iraq and inspire attacks in the region, Turkey and Europe.

Not intervening was the right choice

History will likely be a cruel judge of the Obama administration's risk-aversion on Syria. Nobody will understand how the administration could not have done more in the face of the largest single refugee flow since the end of the World War II, the hundreds of thousands killed and the destruction of an entire society.

That with the exception of Bosnia and Kosovo, Presidents past refused to intercede in the face of mass killing from the Armenian genocide to the Nazi Holocaust to Cambodia; to Rwanda, Darfur, and Congo will be conveniently forgotten. Nor will the President's critics honestly admit that identifying a serious strategy to change the political and military balance on the ground would likely have required a massive commitment of resources that neither they, Congress, or the American public seemed ready to accept, particularly in the wake of failures in Afghanistan and Iraq.

Still, the image of a failure to counter Russia and Iran will likely stick the outgoing administration like a barnacle to the side of a boat.

Will the New Administration benefit from this?

Quite possibly. Syria will remain a fractured state and like Humpty-Dumpty, it's not going to be put together anytime soon.

But Russia backed Syria's military victories and Trump's focus on defeating ISIS and not on removing Assad or supporting his opposition will open up the prospects of much closer US-Russian cooperation -- rather than competition over Syria.

Trump seems to be willing to allow Putin to take the lead in Syria as the senior partner and if Iran, Turkey and Russia manage to create a political process that reduces the killing and conflict, the Trump administration will be the beneficiary.

JUST WATCHED Syria opposition hopes for new tack with Trump Replay More Videos ... MUST WATCH Syria opposition hopes for new tack with Trump 04:39

If that happens, the new President will almost certainly claim that it was his decision to abandon his predecessor's policy of getting crosswise with Moscow and instead to dance with the Russian bear that saved the day.

The price of stopping the killing and bringing increased stability to Syria will nonetheless be a steep one: legitimizing a cruel dictator and his Russian supporters and leaving Syria in the hands of a man responsible for mass killing, the use of chemical weapons against his own people and the deaths of hundreds of thousands.

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But these downsides seem to play the incoming administration's proclivities to avoid intervention in nations' internal affairs and accept the reality that it can't change authoritarian regimes.

Still, to be fair, the down payment on Assad's staying in power had already been made by an outgoing President who decided several years earlier that the US was simply not prepared to risk getting drawn into another costly experiment in regime change and nation building.

Syria may yet prove to be a painful headache for an incoming President Trump. But even if it does, it is unlikely to be as costly to his reputation and credibility as it will be to Obama's.