Roger Cohen makes a lot of questionable assertions in his latest column, but this one is simply nonsense:

ISIS grew through American weakness — the setting of objectives and red lines in Syria that proved vacuous.

I know that interventionists like to blame everything undesirable that has happened in the last year on not enforcing the “red line” in Syria, but this may be the most absurd attempt yet. Had the U.S. followed through with the “limited” strikes that Obama was threatening last year, that would have inflicted damage on Syrian regime forces and potentially led to a larger U.S. military engagement against the regime. That would have benefited anti-regime forces, including ISIS. Had there been direct U.S. intervention in Syria last summer, it might still be going on now. In the worst-case scenario, the intervention might have “worked” to hasten regime collapse and expose more of Syria to ISIS’ depredations. Backing up the foolish “red line” last year wouldn’t have done a thing to check ISIS’ increasing power, and it would very likely have aided the group and possibly allowed it to seize even more territory. More to the point, enforcing the “red line” would have done nothing to deter or frighten ISIS into behaving any differently than it did. Malevolent actors have their own agency and will usually behave as they see fit, and they aren’t likely to be impressed by the fact that our government has just backed up a threat to attack their enemies. Groups like that probably couldn’t care less whether the U.S. backs up its foolish threats, and they would presumably welcome our habit of engaging in ill-conceived military action that they can exploit for their own purposes.