First, let's start with Bashir Assad, Syria's President. His two allies are (1) Russia and (2) Iran.
Turkey borders Syria, which borders Iraq. Turkey's leader (Erdogen) hates Syria's President Assad and supports "Turkmen" who are Syrians who speak Turkish.
Turkmen are reported to work with other Syrian opposition groups, including the Free Syrian Army (the good guys--moderates), but also including the Islamist group Ahrar al-Sham and al-Qaeda allies al Nusra Front. Their main opposition, however, are the regular Syrian forces (of Assad) and the so-called Islamic State (ISIS), which has branded them apostates and carried out a mass killing of them last year.
Putin's Russian forces have been attacking the Turkmen and other anti-Assad groups instead of ISIS. That's why Turkey shot down one of their fighter-bombers. Putin is attacking the people we support who are attacking Assad, who we don't support. Got that?
On the other hand Turkey hates the Kurds, who live in Turkey, Syria and Iraq. The Kurds hate ISIS and have been driving them back from northern Syria. So, Turkey has been bombing the Kurds, which America counts as allies. So that means one of our "allies" Turkey is attacking our ally Kurds while Russia is attacking their allies and ours too. Don't get dizzy yet, we aren't done.
Around two years ago, there were only a few hundred extremist fighters in Syria and most of them were present in southern areas close to Iraq. The moderates opposing Assad formed the Free Syrian Army (FSA) in 2011, following peaceful protests in Daraa and Damascus, for the purpose of confronting the brutality of the Syrian regime.
Kurds have defended their own territory from the ISIS, backed by raids by the US-led coalition with Syria's Kurdish People's Protection Units (YPG) in the north and northeastern Syria, and peshmerga in northern Iraq.
When Iran saw the FSA fighting around Damascus, it did the same thing and sent Hezbollah militias there. It also assigned generals from the Iranian Revolutionary Guards (Shittes) to establish similar extremist groups from Iraqi and Afghan organizations, among others, and sent them to Syria. So Iran has committed its elite troops, the Revolutionary Guards, in Syria with some 7,000 soldiers, who are also in Iraq.
Confused yet? Hang on, its about to get more complicated.
ISIS had already considered all parties to be its enemy and it even fought the FSA more fiercely than it fought Assad's forces. In short, ISIS hates everyone and everyone hates ISIS! ISIS has its own view of inducing an Armageddon scenario, which sounds a lot like certain Christian groups.
According to its online propaganda magazine, "Dabiq," the ISIS believes that it will eventually emerge victorious in the war against the infidels, culminating in a final end-of-days battle in Dabiq, near the northern city of Aleppo. The Washington Post notes that in each edition of the ISIS magazine features the same prophetic quote about how things will unfold: "The spark has been lit here in Iraq, and its heat will continue to intensify — by Allah's permission — until it burns the crusader armies in Dabiq."
Assad's Syrian army numbered 178,000 troops in 2015, according to the International Institute for Strategic Studies (IISS), about half of what it once was. To this day, his helicopters are dropping "barrel bombs" in cities that blow up entire buildings, and have killed over 250,000 Syrian civilians and created over 4 million refugees that now live in neighboring countries as well as those now flooding into Europe. It's estimated only 6% of Syrian refugees have made it to the west so far, meaning we still have a significant problem.
So, in summary, we have Turkey, the United States/France and Russia -- each targeting different groups in Syria! It is a bizarre bazaar of conflict.
Like I said it's complicated. Simply "pulling out" won't fix it --since the neglect to take decisive action simply led to more deaths and increased the number of displace Syrians and refugees.
Adding foreign troops on the ground would be an ISIS dream as it would sharply increase their recruiting by giving legitimacy to their argument that this "is a war against Islam" when it is not a war against a religion but against extremists using that religion for their own twisted purposes. Don't give them what they want. Arab troops need to do this ground work.
As we saw in the downing of the Russian jet, this war could have severe unintended consequences. Armageddon could be one of them.
Stay tuned for updates in this fast changing, dangerous situation.