THE MESS IN THE MIDDLE-EAST
I'm more inclined to put it down to (the more recent) arbitrary carving of territories and drawing of border lines by the powers of France and Britain at the end of WWI. Exacerbated by installing puppet governments in whatever entity they'd created to fit their interests.
Frictions between adherents of Shia and Sunna notwithstanding, they haven't gone to all out war with each other over religion since the battle of Karbala. Past conflicts as well as the present ones in (primarily) Syria and Iraq were and are about politics (power and influence) more than about anything else.
Subsequent to the Ottoman Empire, that had reigned for more than six centuries, what were they to do? Uncle Sam was only interested, at the time, in Saudi oil.
The countries involved in the aftermath of WW2 could not have been left alone, and the only way forward was to enlist the help of "strongmen" who had the physical strength (in numbers on-the-ground) to maintain the peace after 1922. What happened was the factioning between sunnite and shiite populations, each of which tried to take control of its bit. Which ended-up with "enclaves" of sunnites some places and in control of three countries despite the fact that they were in fact minorities in those countries.
This was a recipe ultimately for the implosion that occurred.
The discovery of oil cemented powers into place throughout the region. Europe and the US were pleased to maintain the Oil-dominated Status-quo. And the (subsequent to al-Qaeda's attack on the US) introduction of America first into Afghanistan (after the debacle of the Russians there) upset the apple-cart once again, as did the invasion of Iraq for no justifiable reason except to overthrow Hussein.
Uncle Sam made a shambles of the situation, and ISIS simply took advantage of the mess to establish itself. Let us not forget that ISIS was formed in a US internment camp near Basra of Sunnite Army officers. Upon being released they went to Baghdad, then cleverly took the oil-fields of eastern Syria to fund their Army. (That the Assad family of Syria could no longer defend, and who were Shiites in control of a Sunnite country. Which is still the problem there exacerbated by the Russian military presence.)
Whilst Uncle Sam high-tailed it from Iraq leaving an incompetent Shiite to rebuild it, which he did by alienating the entire Sunnite community and installing a Shiite governance. See WashPo article
here. So, the Sunnite communities started "dealing" with ISIS across the north of Iraq, because it had become the dominant power in the area - until the Kurds stopped their eastward expansion.
And it is the Kurds who are leading the effort to retake both Mosul in Iraq and inevitably Raqqa - ISIS headquarters in middle-Syria.
Uncle Sam has nobody but himself to blame for the Mess in the Middle-east. Putin waltzed in to protect his sea-port at Latakia (home of Assad's Shiite community) and only possession on the Med (as does the US in Naples with the Sixth Fleet).
For as long as oil is the dominant factor in the Middle-east, there can be no settling of the matter between Russia and the US. If oil prices stabilize at their lower price at present, that could happen sooner rather than later as each country settles into a pattern based upon present religious dominance of secular matters.
MY POINT?
One can see the parallel of religious interference historically in politics both in Europe and the Middle-east.
Strategically, the US should have undertaken an evolution from fossil-fuels to nuclear or other sources of energy in the 1960s. But it did not do so under pressure from BigOil interests ...
________________________
