Not only is the battle for Aleppo sending tens of thousands of desperate people fleeing toward Turkey, but the fall of the rebel-held city would deliver a major blow to Ankara's Syria policy.
Syrian government forces, backed by Russian air power, have cut off the last major supply route to rebels in Aleppo. The route, known as the Azaz corridor, links rebel-held eastern Aleppo with Turkey.
If the corridor falls, the rebels could lose Aleppo -- and the entire Turkey-Syria border could fall under the control of forces that Ankara hates: the forces of President Bashar al-Assad
's Russian-backed regime, and the Kurds.
Russian involvement has altered the course of the Syrian civil war
for Turkey. Just a few months before Russia entered the war, Turkey and the United States had agreed on the outlines of a de facto "safe zone" along the Turkey-Syria border.
The deal was expected to significantly increase the scope of the U.S.-led air war against ISIS
in northern Syria.
The agreement aimed to drive the so-called Islamic State out of a 68-mile-long area west of the Euphrates River and reaching into the province of Aleppo.
Ankara hoped that with the deal, the Kurdish expansion in the north would stop, the Syrian opposition would gain ground and fully capture Aleppo, and the Assad regime would be weakened. Turkey even reportedly trained a militia that would be tasked with policing the safe zone.
Putin upsets plans
Russian involvement, however, upended Ankara's expectations.
A no-fly zone became very risky after Russia deployed S-400 missiles in Syria.
Complicating matters further has been Ankara's shooting down of a Russian jet when it violated Turkish airspace in November. After the incident, Moscow directed its firepower on Turkey-backed rebels, including the Turkmens, who are an ethnic minority of Turkish descent and have emerged as Ankara's favored proxy force, across Idlib and Aleppo.
Moscow ramped up air operations near the Turkish border, forcing Turkey and the United States to suspend aerial operations in northern Syria.
Moscow also courted Syria's Kurds. In December, Russia delivered weapons to the 5,000 Kurdish fighters in Afrin, between Aleppo and the Turkish border.
And Russian President Vladimir Putin
offered to help the Kurds consolidate their territorial gains in northern Syria by linking the Kurdish-held town of Kobane with Afrin.
Russian cooperation with the Syrian Kurdish group Democratic Union Party, or PYD, came against the backdrop of a close partnership between the PYD and the U.S. in Syria.
U.S. support for the Kurds in its fight against ISIS has heightened Turkey's fears of an autonomous Kurdish region along its southern border and escalated the tension between Ankara and Washington.
Turkey recently summoned the U.S. ambassador to express its displeasure after a State Department spokesman said Washington did not regard the PYD as a terrorist organization.
Turkish military intervention?
For now, the rebel supply lines to Aleppo are open, since the border crossing at Bab al-Hawa is still under the control of Turkey-backed forces, but that might not last long.
If regime forces capture the area west of Aleppo, Turkey will find itself cut off from the rebels it backs inside Syria.
Tens of thousands of Syrians are currently massed at the Turkish border fleeing regime's Aleppo offensive.
Already shouldering the burden of over 2 million refugees, Turkey fears the fall of Aleppo will send many more fleeing toward the border.
Turkey's worst-case scenario might unfold if the Kurds seize the opportunity to carve themselves an autonomous region stretching from the Iraqi border to Afrin in the west.
Some have suggested that such a scenario would spur a Turkish military intervention in Syria.
Tempting as it may be for President Recep Tayyip Erdogan
, who recently hinted at the idea, a unilateral or a joint Saudi-Turkish military action in Syria is highly unlikely.
It is politically and militarily too risky.
The Turkish military is fiercely opposed to intervention without international legitimacy and U.S. backing.
Playing on Europe's fears
With Moscow-Ankara tensions at all-time high and Russian air operations in northern Syria, the military leadership does not want to provoke a military confrontation with Russia
A Turkish army operation to evacuate troops guarding a historic tomb last year revealed an uncomfortable reality for Turkish military: Any operation inside Syria required cooperation with the opposition and the Kurds.
Reportedly, Turkish forces in armored vehicles were able to enter northern Syria through a corridor opened by the Kurdish forces. The military is reluctant to put itself in a similar situation again.
Intervention is politically risky as well. At a time when the government's Syria policy is highly unpopular and Erdogan is preparing to ask voters to approve his dream of switching to a presidential system, intervention in Syria is likely to spur a negative public reaction.
Erdogan last week hinted that Turkey could take part in a U.S.-led military operation in Syria
But given the Obama administration's cautious approach so far, such an operation does not seem to be on the horizon.
Turkey's best bet could be stepping up its support for the opposition and pushing for a no-fly-zone inside Syria.
Turkey has been hedging its bet on the European Union
by playing to Europe's fear of a new wave of Syrian refugees.
Ankara recently renewed its bid for a no-fly zone, arguing that such a zone would be the most effective way to stem the flow of refugees.
The EU, and most notably German Chancellor Angela Merkel
, who bears much of the burden with increasing numbers of refugees, may support the idea. But Ankara's demand is likely to fall on deaf ears in a risk-averse Washington.
Turkey has so far refused to recalibrate its Syria policy, but the facts on the ground might soon leave Turkey without any other options. The Aleppo offensive signals that scenario might not be too far off.