Assad is Shia. Sunnis are against him. Caliphate is Sunni thing.
Caliph is a Muslim thing. They're just fighting over who gets to sit in the big chair.
Is Turkey Sunni?
Yes, Assad is Alawite. They are a strain of Shia.
I think we must remember that daddy Assad cam to power in a military coup where they overtook the Baath party, a socialist group. (The non-military elements of the Baath party moved to Iraq, where they were again ousted by a military coup after gaining power, specifically by some chap named Hussein.)
I believe that the former KGB major, currently running Russia, likely has a long and deep seeded affinity for the socialist and progressive Baathist Syrian power block. (By the by, those are their own party descriptions not mine - the accepted parties in Syria are the Baath socialists, and the National Progressive Front.)
However, the Assads, as Alawis, have never gained the acceptance of the larger Arab community, despite their pan-Arab populist rise to power. This is largely due to their religious holdings, which while ostensibly Shia, are seen by most Muslims (both Shia and Sunni) as heretical.
The islamists see Syria as an opportunity. With more than 80% of the country holding a more traditional Muslim view, they see a future for Islam on the doorstep of Europe through both the land bridge and their Mediterranean ports.
Putin sees the same opportunity, and is in my opinion, intending to complete the work started in ‘63: to finally and fully establish Syria as a dependent socialist puppet. Oil, a southern vector to Europe, and a Mediterranean presence are the gems that make an otherwise desolate desert shine for the opportunists.
Where the Islamists view opportunity in the majority non-Alawi Muslim population, Putin sees the chance to prop up a minority dictator, offering him protection from the gathering masses.
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The fact that our current leadership can’t see this amazes and appalls me. I must conclude they are either willfully ignorant, completely incompetent, or they have chosen the traditionalist Muslim solution without due regard for the consequences of a Mediterranean theocratic Islamic state. A combination of the three is also a possibility...