The logical result of Obama’s policy — which amounts to a kind of warfare-lite — is mission creep and gradual escalation. Send in a few more troops. Allow them to go on patrols with the Iraqis. Let them lead by example. Send in a few more. You might recognize this road; it can lead to another Vietnam.

What are the alternatives? One would be to resurrect Colin Powell’s doctrine of overwhelming force: Send in enough troops to drive the Islamic State out of Iraq once and for all. We conquered and occupied the country once, we could do it again.

But the Islamic State would still hold substantial territory in Syria — and thus present basically the same threat as now. If our aim is really to “destroy” the group, as Obama says, then we would have to wade into the Syrian civil war. Could we end up fighting arm-in-arm with dictator Bashar al-Assad, as we now fight alongside his friends the Iranians? Or, since Obama’s policy is that Assad must go, would we have to occupy that country, too, and take on another project of nation-building? This path leads from bad to worse and has no apparent end.

The other choice is to pull back. This strikes me as the worst course of action — except for all the rest.