Let's remember that we have two major enemies in the Levant

 . . . and not seek to collaborate with one of them against the other.  So says Jonathan Spyer at PJ Media.  He starts his piece with some rather grim reports coming out of IS-held areas concerning wiping out the male populations of towns and selling the women into slavery.  He then notes the gains made by the US-backed ostensible central government, so that Erbil and Baghdad are for the time being off-limits to the jihadists.

But then he looks at the full scope of players in the region:

Is the president just talking, and will the Islamic State be permitted to continue in existence, at least west of the Syria-Iraq border?  Or is it possible that when the president refers to creating the right “regional” situation to allow for the defeat of “ISIL“ he is referring to the one power that potentially could organize a ground attack on the Islamic State? That country is the sponsor and ally of the two governments that exist to the west and to the east of the boundaries of the Islamic State — that is, the Assad regime to its west and the Baghdad government to its east.

The country in question is Iran, which has a clear interest in the destruction of the Islamic State. The IS domain, if it continues to exist, stands between Iran and its desire for a contiguous line of pro-Iranian entities between the Iraq-Iran border and the Mediterranean Sea. The problem is that an Iranian victory over IS would mean a general Iranian triumph in the Levant. That’s a bad outcome too.

The fighting in Amerli this week, in which Iraqi special forces and Shia militias helped by USAF air cover defeated IS forces may be an indication of what is to come. If so, the result will be to hand Iran a strategic victory in the Levant and Mesopotamia.

A policy of dual containment — strengthening reliable allies in Kurdistan, Jordan and Israel — to contain both Shia and Sunni Islamists should be the road map guiding western policy in this area today.  The only alternative to this would be the entry of U.S. and allied ground forces to destroy the Islamic State. This is clearly not an option.

But a tacit alliance with Iran, in which western air power cooperates with Iran-supported, mainly Shia Islamist forces on the ground against ISIS would be among the worst possible options. It is possible that inertia or design is leading policy in this direction.

So it needs to be said clearly: The Islamic State and the Islamic Republic are both enemies of the west and of the peoples of the Mideast. Backing one against the other would be a disaster.

I know it doesn't take much for Secretary Global-Test to be seduced into appeasing the mullahs, but surely a more steely-eyed strategic view will prevail.