The if-only-we'd-intervened-more crowd has a new argument: If Washington had shipped arms to the rebels in Syria—more arms, that is, than it already gave—it might have stopped the rise of ISIS. Marc Lynch, a political scientist at George Washington University, disagrees:
In general, external support for rebels almost always make wars longer, bloodier and harder to resolve (for more on this, see the proceedings of this Project on Middle East Political Science symposium in the free PDF download). Worse, as the University of Maryland's David Cunningham has shown, Syria had most of the characteristics of the type of civil war in which external support for rebels is least effective. The University of Colorado's Aysegul Aydin and Binghamton University's Patrick Regan have suggested that external support for a rebel group could help when all the external powers backing a rebel group are on the same page and effectively cooperate in directing resources to a common end. Unfortunately, Syria was never that type of civil war.
Syria's combination of a weak, fragmented collage of rebel organizations with a divided, competitive array of external sponsors was therefore the worst profile possible for effective external support….An effective strategy of arming the Syrian rebels would never have been easy, but to have any chance at all it would have required a unified approach by the rebels' external backers, and a unified rebel organization to receive the aid. That would have meant staunching financial flows from its Gulf partners, or at least directing them in a coordinated fashion. Otherwise, U.S. aid to the FSA would be just another bucket of water in an ocean of cash and guns pouring into the conflict.
Lynch goes on to explain why that sort of coordination would have been just about impossible at the time; to read the rest of his post, go here. Then read this piece by Hisham Safi, which describes how Western assistance to the rebel councils in areas taken from Bashar Al-Assad's control went awry, with the would-be rulers spending more time angling for aid dollars than building institutions that were responsive to local needs and able to withstand ISIS' assaults. And then go here for a reminder that ISIS is "fighting with hundreds of millions of dollars of U.S. military equipment seized from the Iraqi Army who abandoned it." If you suspect that sending more military aid to Syria would have ultimately meant more American arms falling into ISIS' hands, you're not alone.