Turkey. It should be clear by now that Turkey has no interest in defeating IS (ISIL, ISIS, Daesh). Indeed all of the time that IS is fighting the Syrian Kurdish forces (YPG) Turkey will support IS, as it has been doing throughout the conflict. It continues to allow weapons, supplies and jihadi fighters to cross its frontier into Syria. At the same time it allows convoys of tankers, loaded with crude oil produced in IS held territory to cross the frontier in the other direction.
Turkey's ambitions seem to be (a) the defeat of the Assad regime in Syria; (b) dismemberment of Syria; and following from that Turkish seizure of territory in northern Syria, ideally to include Syria's second city of Aleppo. The aim of this putative annexation is not only territorial aggrandizement, but also, and perhaps mainly, to prevent the Syrian Kurds holding a contiguous strip of land on the southern side of the Turkish border, the northern side of which is home to a large number of Turkish Kurds. At present Turkey has only demanded a "no-fly" zone in northern Syria, with the claim that it would be a place where refugees could safely shelter. Erdogan has been trying to sell this idea to the EU, which quite reasonably wants to stem the flow of refugees, through Turkey and Greece. It is true that Turkey has a serious problem with refugees, but at present it seems to be using the refugees mainly as a tool to coerce EU support for its no-fly zone (plus extorting the huge cash payment, which Angela Merkel offered, along with the carrot of eventual Turkish entry into the EU). Things seemed to be swinging in Turkey's direction until Russia entered the fray.
Russia. Russia has had cordial relations with Syria dating back to Soviet times and the reign of Assad pere (Haffez). It has long had a naval base on Syria's Mediterranean coast, indeed its only such base on the shores of the Mediterranean. The possibility of the Assad regime falling and a US backed regime taking its place has no doubt caused considerable concern in Moscow. So this is an important reason why Russia has backed the Assad regime. Another reason I believe is that it is profoundly worried about Washington's proclivity for instigating regime change in countries not on its side. It has seen this happen in Iraq, Libya and Ukraine and perhaps not unreasonably sees itself as a potential target if these activities are not checked. I believe Russia felt that it had been tricked and betrayed over Libya when it voted in the UN Security Council for air strikes to protect civilians in danger and found instead that NATO carried on an air war to oust the Qaddafi regime.
Russia also has a genuine fear of jihadi extremists growing in power in Syria. It has a very large Muslim population and is surrounded all along its southern border by Muslim states. It has fought jihadis twice in wars in Chechnya and against the US backed mujahaddin in Afghanistan. It fears the growth of IS and its potential for turning attention northward to Russia, especially as numbers of Chechen, Uzbek and other Central Asian jihadis are reportedly fighting in Syria.
Russia has international law on its side when it says that the Assad government is the recognized government of Syria, and it is fighting against an insurgency at the invitation of that legitimate government.
In its arial campaign in Syria Russia has targeted groups fighting against the Assad regime, not just IS. This has seriously upset the US, who maintain the fiction of a "moderate opposition" and especially of Turkey, who sees its close relationship with the Turkmen militias fighting along the Turkish border, being disrupted. The fiction that these are "moderates" was exploded with the publication of video of their fighters chanting "Allahu Akbhar" over the half-naked body of the Russian pilot they had recently machine gunned as he descended in a parachute.
That the shooting down of the plane was carefully planned in advance seems beyond doubt. Emre Uslu, a Turkish writer, here (http://www.informationclearinghouse.info/article43532.htm)
describes how the Turkish public was primed through a media campaign in the days before the downing of the jet. The fact that there were Turkish TV news crews on hand to film the shooting down and the fact that the government had radar traces at the ready, all lead to the same conclusion of a well-planned event.
The United States. Whether the US knew in advance of the shooting down is not known. However it does seem unlikely that Turkey would do something like this without first informing the US, especially as the Turks immediately called for NATO support. There certainly would be many factions in US power circles who would like to see Russia discomfited. Russia's intervention into Syria had upset US calculations as much as it had upset Turkey's. The US policy in Syria seems to be disingenuous at best. It has backed the idea of regime change from the start and the CIA has been supplying weapons and support to opposition groups. There are even claims that the CIA was behind the first violent protests against the government to which it responded rapidly and brutally. At first the US seemed to believe that there was a non-extremist opposition to Assad which would take power once the government was toppled. But as the war progressed whatever moderates there were seemed to be overwhelmed and subsumed into the more determined and violent jihadi groups. David Cameron may claim to believe that there are 70,000 "moderates" fighting the Syrian Arab Army, but very few others do.
But it seems that the CIA was prepared to continue arming opposition groups, even when they knew they were of the jihadi persuasion. They even knew of the emergence of IS and did nothing to prevent it, indeed may have encouraged it. A Pentagon secret document of 2012 (declassified under pressure from Judicial Watch) states
“…there is the possibility of establishing a declared or undeclared Salafist Principality in eastern Syria (Hasaka and Der Zor), and this is exactly what the supporting powers to the opposition want, in order to isolate the Syrian regime, which is considered the strategic depth of the Shia expansion.”
It seems to be the same strategy that the US had used with the mujahaddin in Afghanistan i.e. arm any group, no matter how unsavoury, as long as they are the enemy of our enemy. This policy came back to bite in Afghanistan, with the emergence of the Taliban and Al Qaeda, and it seems to be doing the same in Syria/Iraq with IS. Indeed it was only when IS started murdering US and other foreign citizens in the most barbaric fashion, that the US felt obliged to take any action against IS. But it has been doing in it in a most disingenuous way, for example allowing IS convoys of oil tankers to regularly transit to the Turkish border. While there is no doubt many different opinions within the US government on how to proceed, it seems to me that defeating and replacing Assad is still the dominant one. Enough bombing of IS is done to prevent a public outcry, but I don't think Washington wants the complete defeat of ISIS because it is an enemy of Assad. Also I believe that there is large contingent of Israeli fifth columnists within the US power structure (the Neocons) who are happy to see an ongoing war in Syria in which the Assad government and its Hezbollah allies are seriously weakened. Indeed it seems that Israel has the permanent annexation of the Golan in its plans, and has been clandestinely supporting IS. In October an Israeli colonel was captured by Iraqi forces fighting with IS in the Salahuddin province of Iraq. This article gives details including name, serial number etc.
No doubt the anti-Assad faction in the US were very unhappy when French and Belgian terrorist conducted their attacks on Paris and IS claimed to be behind it. People started demanding the destruction of IS, and some wondered publicly why the US and its NATO allies had not been more successful in defeating it. Which leads us to France.
France. Until the November 13 attacks on Paris, France seemed to be squarely on the same side as Turkey and the US - the defeat of Assad was their main goal. But the attacks seemed to have concentrated the minds of M. Hollande and his government. Now they realize that their real enemy is IS, not Assad. President Hollande has stepped up French bombing of IS and has dispatched France's aircraft carrier to the eastern Mediterranean to add to the fire power. He has agreed with President Putin to coordinate French and Russian arial actions against IS. Furthermore some members of the French government have stated publicly that the Syrian Arab Army of Assad could be of considerable use in fighting IS. No doubt this is not what Washington wanted to hear, and certainly not what President Erdogan of Turkey wanted to hear.
With the Paris attacks the world is waking up to the fact that IS is a much bigger menace than the Al Assad regime. The latter has not declared jihad on Christendom, nor has it bombed civilian airliners or sponsored terror attacks in European and Middle Eastern capitals. Indeed the Syrian regime possesses a sizeable battle-hardened army which, with arial support and in alliance with Kurdish factions could no doubt defeat IS and deprive it of all territory. Will it happen? I doubt it. The CIA and other Washington warriors don't like to lose. Will Erdogan get his "no-fly" zone. Again I doubt it, not with Russia now fully committed to fighting against his plans. It looks like the war could go on for quite a while longer, but I can't help feeling that it is swinging against the US-Turkey-NATO-Saudi side.