Interesting.
I am wondering if the 'withdrawal' isn't so much an actual withdrawal as a shifting of resources applied.
The effectiveness of fixed wing air power on the likes of ISIS has always been questionable.
The US and allies have had scant success with air strikes in checking ISIS gains on the ground, and TBO, I also have doubts about just how much impact strategic Russia air strikes are truly having on ISIS.
The very best smart bomb is only as reliable as the targeting intel. Organisations like ISIS are forced to learn counter surveillance very quickly and very well, as failure to do so ends in death by air strike.
If coalition jets with smart bombs cannot get some ISIS leaders deep in ISIS territory, I have little confidence the Russians can somehow nail them with free fall bombs.
I think the big game changer of the Russian air campaign has been it's co-ordination with SAA and other loyalist ground forces.
With ground forces support, not only do you get reliable, timely targeting information from front line troops and observers, but you can also work with friendly ground forces to pin enemy forces in place to be splatted by air strikes, or flush them from cover with air strikes so the ground forces can have a turkey shoot etc.
The key to loyalist successes has been CAS. I think it is noteworthy that the Russians are leaving all their CAS birds in place, while removing the deep penetration strikers like the Su34, while at the same time bring in more dedicated CAS assets like the Ka-50 pictured.
To me, that doesn't look so much like a withdrawal as a restructuring of forces deployed.
I think the Su34s have proved less than satisfactory, so they Russians are pulling them. But they don't want to admit that, so they put a nice piece of spin on it.
The bulk of the withdrawal appears to be the ground troops Russia originally deployed to bolster security at their main base, and also as a potential direct intervention force should the situation get that bad.
Given the big gains loyalist forces have been making in recent months, there is now almost no threat of ISIS being able to mount a direct, large scale frontal assault on the Russian base, nor do the Russians need to fight on the ground to keep Assad in power, so those ground troops are no longer needed in Syria.
Pulling them out not only makes logistical and economic sense, but also provides a brilliant piece of propaganda and misdirection to take the west completely by surprise, so everyone is asking the question Russia wants them to ask - why are the Russians pulling out of Syria, instead of the ones they probably should be asking - why are the Russians pulling XYZ assets out and not ABC?