I would renounce the goal of overthrowing Assad. This is illegal, stupid, and unnecessary. I have yet to see anyone defend this policy, or for their part, seen the complicit media push the question.
I would remove all of ISIS sources of income. I would bomb their oil production, storage and transportation infrastructure until every tanker in their region stood empty because no one would drive them.
I would ask for a volunteer force of at least 2,000 Special Operations folks, and give them all the support–particularly air cover–they needed, and tell them to go hunting. I would make this a multi-national effort, and although I would want to keep ultimate control over my guys, I would be willing to insert them into a larger joint task force.
I would create an informational campaign to appeal to the civilized, decent, liberal sentiments in particularly the Western populations. Kids who grow up here by and large do not want to see adulterers stoned, and homosexuals decapitated. They do not condone slavery, rape, and conquests intended for pillage. I would employ theologians to figure out how to deemphasize what I would call the demonic elements of their religion at its worst, and the angelic elements of it at its best, which I see embodied in the work of the Sufis. Most of them were very Muslim, but they focused on a relationship with the One True God, and not so much on killing, raping, and stealing. No sane person can defend those practices, even if they were equally common among Christians in the 7th Century. That was a very long time ago.
I would treat all calls for subverting the Constitution in the United States–which is what the call for Sharia is–as treason. I would arrest and jail anyone who publicly proclaimed this. We have tolerated open treason for far too long.
And I would convene a panel of the worlds most powerful and wealthiest nations, and ask them: what do you want the world to look like in 20 years? Where do WE want it to go? Have we not had enough bloodshed? Can we not call Communism a failure in building a better world? Can we not grant that freedom is the precondition of any form of dignity for human beings, and its alternative an abomination we should rightly reject?
I would do much more than this–this is just dealing with Islam’s tendency to spin out of control–but this would be a start.
Edit: one thing you will note is that I did not include “bombing”. Bombing is the tactic used by those who want to create the impression they are doing something, but who are not committed to final victory. It is not my belief that we need to retake all of ISIS lands with large Army units. It is my belief that these smug bastards can be made very scared, and to spend most of their time hiding, by an all volunteer force. That will choke recruitment, and economic violence will choke revenues. Sooner or later, it will stop seeming like an adventure, and only the goat fuckers will be left, and they will not be hard to deal with.
I have a particular affinity for the Australian SAS. I suspect no American or European Leftists want to know this, but senior NVA commanders left fairly extensive notes on what worked and what didn’t. As far as what worked, the Aussies scared the shit out of them. Americans would send out patrols, make contact, call in air power or artillery, then leave. The Aussies would stay in place. They would remain silent. And they would engage them again and again at close range. One Spec. Op guy I know said the Aussies he knew in Afghanistan would go on six month patrols. That is the sort of thing I have in mind. A sustained commitment, by volunteers. People who blend, who study their enemies up close, and who, when ready, bring death and destruction.