In Syria we have a religious civil war. 40% of Syrians back Assad they are all more or less non sunni muslim or Christian.
http://www.understandingwar.org/sites/default/files/PieChart13Dec.jpg
The pro Assad are a unity of minorities that don't want Sunni rule. I cant see how the world could have done anything, To go in and create a democracy and expect the emotions of hatred to just go away?
Democracy is fairly stable in Muslim countries when the population is predominantly one sect of Islam. for example and Tunisia, Lebanon, Turkey, Kuwait and Iran (to some degree) all have a predominante religion.
In Syria like with Iraq the Sunnis will vote for the Sunni candidiate and the Shia will vote for their Shia candidate more or less. Hopefully things will change.
We didn't do enough to arm and train the moderate rebels and to actively help them. Even though using ground troops sucks because it results in casualties it is necessary for an effective campaign. If we told Assad we would invade to get rid of him unless he went peacefully and were serious then I don't think he would have pulled a Saddam and ran to hide in a hole in the ground he would have chosen life in exile.
We could then have helped the Free Syrians set up a government and promise a democracy for all. The Islamists didn't want that so would have resisted but it would just have been a repeat of the failure of Al Quaeda in Iraq.
Instead ISIS killed a lot of the moderates and worse have been heavily funded by rich Muslims and have become even richer as they loot the areas they take over.
The West ignored ISIS instead of actively taking efforts to squash them.
Gringo is lying about our finding of rebels allowing ISIS to grow in power it was are lack of support that allowed it:
"The moderate rebels in Syria called on Washington to send heavier artillery for months even before ISIS gained ground last summer. That aid never made it to the battlefield. And when ISIS bulldozed the border between Iraq and Syria in June, the rebels in Aleppo had to fight on multiple fronts, against Assad, ISIS and al-Nusra, with dwindling resources.
Recipients of U.S. lethal aid told IBTimes in interviews that the U.S. set them up for failure.
“The U.S. support was not enough for the rebels in the North to be strong and defeat the Islamic groups,” said Oussama Abu Zayd, one of the main advisers and an active member of Harakat Hazzm, adding that many moderate rebels defected to extremist organizations because they had more money. “They have millions of dollars from donors.”
http://www.ibtimes.com/us-backed-moderate-syrian-rebels-north-defect-obama-strategy-set-back-1839604Each day we sit on our hands the larger the problem grows and ultimately the larger the military force that defeats them will have to be.
A sizable military force should be at the Iraqi border preventing any resupply form Syria and to prevent retreating into Syria they could be the anvil. The hammer would be other forces to encircle the ISIS fighters. You surround them and force them to either give up or you go after them and kill them.
Without Western forces this will take a lot more time and effort.
That won't be the end of course someone needs to go into Syria to clean them up. Just dropping some bombs from the air isn't going to do it.
The more established they become the larger the force they can field and the more effort it is going to take to defeat them completely.
Even if Iraq eventually manages to recapture its land without Western military power it doesn't end the ISIS threat because they will still have a large swath in Syria. Someone needs to invade Syria to clean the out. Sooner or later someone has to do it. The longer you wait the bigger the task becomes.