The US is attempting to fight a war in Iraq and Syria under rules of engagement that avoid war crimes. It seems hard to disapprove of this, but I do tend to thing that it ignores a basic truth. War is intrinsically a crime, bloody and indiscriminate murder. Trump is a dangerously fascist personality, but he taps into some fundamental aspect of humanity when he advocates murdering the families of terrorists and a more bloody minded approach to ISIS.
World War II was, among other things, a nearly all out war against civilian populations. The American Civil War ended only when Sherman burned his way through Georgia, making it clear that the alternative to surrender was death by starvation.
Our attempts to fight a more humane war have been spectacular failures, not only failing to subdue the enemy but proving massively inhumane in their execution. The Syrian catastrophe is the classic example. Our attempt to just fight bad guys and split hairs has had us fueling more violence, much of it inflicted with weapons we have supplied to all sides. Allowing ISIL to occupy territory has made it a global beacon for terrorists and world wide terrorism. Our attempts to get proxies to fight a war has created what amounts to feuding warlords.
A fundamental principle of American warfare has always been, if I may borrow a well-worn cliche, is to go big or go home. If fundamental American interests are not involved, going home is the obvious choice. If we want to do state building, and our attempts to date in the Islamic world have been disastrous, the same rule applies. Plan for generations, and plan to control nearly every aspect of society, as we did in Japan and Germany after WW II.
I favor disengagement and going home. In the case of ISIL, which conducts world wide terror, we may not have that choice. Here is one crazy idea: make it an offer it can't refuse. Stop American interference in return for a guarantee of safety for Americans there and here. As an alternative - utter annihilation.