Albeit the Americans are so far only flying novel "show of force" missions without actually firing at ISIS
On November 16 US announced it would no longer militarily back the Turkish army and Turkish-backed rebels in northern Syria. It did so over displeasure that Turkish forces in Syria were pounding the Kurdish-dominated SDF (which is America's main proxy army against ISIS) as much as ISIS itself.
However, since then the Americans have reversed themselves, and are back to flying air support for the Turkish forces (albeit in characteristically Byzantine fashion have not owned any strikes).
December 30 Turkish foreign minister claimed US had struck ISIS in al-Bab following a Turkish request. At the time US neither confirmed nor denied this. Since then however, Pentagon spokesman has explained that US indeed launched "flights" to support the Turks:
QUESTION: Has the U.S. coalition or U.S. aircraft supported Turkish operations in al-Bab?
PETER COOK (Pentagon Press Secretary): My understanding that last week, there was a request. When some Turkish forces came under fire for -- for air support and there was -- there were flights conducted by the coalition at that time.
However, here comes the "good" part, US also claims the jets it launched did not actually release any ordnance but merely offered moral support for the Turks by conducting "a visible show of force" on their behalf:
Q: You mentioned as a -- as -- you mentioned as a flight, rather than a some kind of strike. And we haven't seen any kind of strikes around al-Bab from the coalition data releases. So is it just some kind of a sortie that you conducted down there or does the -- does the aircraft conduct in airstrikes?
PETER COOK: My understanding of that was there was not a strike specifically, but there were aircraft involved in that effort, a visible show of force if you will, by coalition aircraft. And we continue to talk with the government of Turkey about the appropriate level of support for the efforts there in al-Bab and that's an ongoing conversations, even happening today.
This is truly ridicilous. So first US was providing fire support for Turks from the air. Then it stopped providing air support. Now it is back to providing air support -- by overflying the battlefield in demonstrative flights.
In any case the Pentagon spokesman also repeatedly said the US continues to talk to Turkey about al-Bab, continues to coordinate with the Turks against ISIS on all levels, values the Turkish sacrifice against ISIS and would like to do everything it can to help Turkey in that effort. In other words US is seriously considering restarting actual strike missions in support of Turkish military in Syria (especially if the Turks agree to go easy on the Kurds for 5 minutes).
Aside from claiming US air strikes on their behalf Turkey has also repeatedly reported Russian air strikes against ISIS in support of its forces on the outskirts of al-Bab. There is no confirmation from the Russian side but the fact the Russians have rebuked the Turks despite repeated opportunities to do so indicates this is likely true. In fact it was also reported by Al-Masdar which relies on sources in Syria.
Reports of Russian air support for Turkish and rebel fighters around al-Bab coincided with the Russian-Turkish brokered ceasefire between the Syrian army and all rebel groups except ISIS and al-Qaeda.
This is a very good deal for the Syrian government and their Russian backers as they remain free to engage al-Qaeda (Jabhat Fateh al-Sham) and therefore dimish the strength of the rebel camp further without violating the ceasefire regime.
It is possible that demonstration of military support for Turkish and rebel forces engaged in combat against ISIS in al-Bab was the price
At the same time it is understandable that Moscow would not want to advertise this fact. It means Russia is now aiding the same military which in November 2015 ambushed and shot down one of its planes on the Syrian-Turkish border and is now aiding an illegal invasion into the territory of its ally Syria.
It also means it is flying air support for rebels which include fighters from Ahrar al-Sham whom it argued just this past September should be considered a terrorist outfit and excluded from the ceasefire regime on the account of its well-documented ties to the Syrian branch of al-Qaeda. -- Albeit to be fair Moscow in the end conceded this demanded to the US in both the February and September cease-fire deals, and it could scarcely offer Turkey worse terms than it had agreed with the US. (Air support for other rebels fighting ISIS is not problematic. Moscow has expressed willingness to do that since 2015 and even claimed number of such missions at the time.)
We see Russia being forced into some of the same compromises in Syria that US has been forced into. Russia needs Turkish cooperation but Turkish terms complicate its relationship with the Syrian government. US likewise needs the Turks on side but Turkish terms would make its relationship with the Kurds impossible.
Nonetheless Russia has the easier time of day because the Turkish intervention rides roughshod over Syrian sovereignty but is actually aimed at the Kurds. Syrian Kurds rightfully regard the Turkish invasion as an existential threat to their ambition of de facto statehood while Damascus might privately appreciate it may even be turned to its advantage.
Also the US has a much harded time at its juggling act because it has pursued multiple goals at once and has therefore at one time fought for and against virtually every side in Syria's four-sided civil war.
The last and only time Americans and Russians have fought a common enemy was in the two world wars when they were incidental allies. Even then they never fought side by side but instead fought separate battles in different theaters.
Since the Russian entry into Syria they have been bombing the same enemy, sometimes over the same battlefields. Nonetheless, they did so without meaning to aid the same ground forces. (Russia aided the SDF but only in their Afrin enclave, whereas US aids the SDF everywhere except in their Afrin enclave.)
With Russia now apparently flying combat sorties on the behalf of NATO Turkey and US military helping out with (admittedly bizarre) "show of force" missions they are now both supporting the same ground forces. They are not friends and they are not allies, but whether they like it or not, they are -- at least in the microcosm of al-Bab -- for the first time in a long time on the same side of a fight.
Once Trump takes power in Washington if he truly follows through with his stated intention to see if relationsh with Russia can be improved he will undoubtedly come under a lot of flak from Democrats.
Best rebuke to that would be pointing out that even if American-Russian relations took a nose dive in Obama years it was actually under his administration that US did something completely unheard of -- ordered its military aircraft on a combat mission in support of a side the Russian military was on.
Yes the suits in Moscow and Washington may only be competing for Ankara's favor. But at a moment when Russian and American pilots both might find themselves risking their lives and multi-million jets to help the same army advance on a little town in Syria what possible excuse could there be for relations between them to be at a 30-year low?