It's just a Turkish ploy to extract western concessions
Turkish foreign minister Cavusoglu says that Moscow and Turkey have "agreed in principle" for Ankara to buy Russian S-400 air defence systems. The minister is even hopeful that the deal will be "finalized" at the Putin-Erdogan meeting tomorrow in Sochi.
We will go out on a limb here and say there is no way this transfer will ultimately go through.
Even if Russians could buy assurances that the Turks won't turn immediately turn around and allow NATO to exercise against their S-400s, Turkish-Russian relations (especially in the air) have been less than ideal.
You will recall that in November 2015 the Turks ambushed and shot down a Russian bomber in Syria after which the Russians beefed up their anti-air capabilities there.
Quite apart from being prospective customers for the S-400, the Turks are in the top three likeliest to meet it from the pointy end.
What we're seeing here is nothing more than theater. For the time being it serves both Turkey and Russia to pretend they're growing so close this could actually happen, but it's all for the benefit of third parties who don't know any better.
Russians certainly don't mind if it looks as if a key NATO member is interested in their wares. It won't hurt their sales, and if it makes the US uneasy about seemingly closer Russian-Turkish ties, that's only a bonus.
Turkey meanwhile is almost certainly talking up the S-400 deal in an attempt to exact concessions from the west. What makes us say that?
Because that's exactly what Turkey was quite openly after in prior negotiations with China.
In 2013 when Turkey started shopping around for a long-range air defense system it was most interested in American Patriot and French/Italian Aster missiles, but wanted technology transfers to go with the actual rockets.
Failing to get that, Turkey announced it had opted for a Chinese arms manufacturer instead, claiming the latter was willing to share the technology as well as missiles.
Ultimately that turned out not to be the case and the deal was scrapped in 2015.
At the time Turkey claimed it would build its own long-range air defense independently, but then last October invited Russia to present its S-400 offer again.
Chances are all three Turkish decisions — to go Chinese, domestic, and Russian — have simply been ploys to get what they really want: technology transfers from their NATO allies.
As for Russia, when the Turks invited them to present the S-400 again Erdogan had just signed onto the Turkish Stream pipeline, was finally fighting ISIS in Syria, and was declining to make a fuss about a Syrian-Russian offensive in Aleppo. So it would have been a very delicate maneuver for Russia to decline.
But privately the Russians must have far more qualms about the deal than they did when they made the original offer in 2013. They also have infinite ways of killing the deal without appearing undiplomatic or slighting Erdogan. There is any number of technicalities they can refuse to budge on to shoot the Turks down before any deliveries are made.