The growing tension between Iran and al Qaeda — what does it mean?

Recently, Iran has been expelling al Qaeda officials who holed up there for years. Bin Laden’s son-in-law, Sulaiman Abu Ghaith, is only the latest example.

U.S. officials and terrorism experts tell the Washington Post that these expulsions suggest growing tension between Iran’s Shiite clerics and al Qaeda’s Sunni terrorists. Yet officials and experts also believe that Iran still permits al Qaeda to use Iranian territory as a transit route to and from Afghanistan.

There was a time when foreign policy “realists” doubted that Iran would cooperate with al Qaeda, and vice versa, given the Shiite-Sunni divide. This view — akin to believing that Nazi Germany and the Soviet Union would never form an alliance — was badly misguided.

But the Nazi-Soviet alliance didn’t hold because their underlying interests were sharply divergent. Obviously, the underlying interests of Iran and al Qaeda also diverge.

The divergence currently manifests itself in Syria. Iran supports the current regime, while al Qaeda linked groups attempt to overthrow it.

Our friends the foreign policy “realists,” along with Paulist exponents of “blowback” theory, might argue that the Iran-al Qaeda rift is related to the diminishing U.S. presence in the region. It’s a plausible argument. One would expect Iran and al Qaeda to have closer relations when their common enemy is a force immediately to be reckoned with. As the U.S. becomes less so, the alliance of convenience becomes less convenient.

This doesn’t mean that the U.S. should become less of a force. Sunni and Shia militants cannot be expected to cancel each other out, at least not in ways that benefit our national security and the stability of the region. Think of Iran and Saddam Hussein’s Iraq by way of illustration. In a sense, they had reached a stalemate. But both both could (and did) harbor and/or support their own sets of terrorists. And both posed independent threats to Israel (Iran especially), to Middle East stability, and (in my opinion) to U.S. interests.

Ten years on, with the U.S. largely defanged in the region, we can expect Iran and its allies to prevail or have major influence in some parts of the Middle East and radical Sunni Islamists to prevail or have major influence in others. In both scenarios, the outcome will be adverse to our interests.

This doesn’t mean the U.S. should intervene in this or that conflict. At this juncture, I lean against U.S. involvement in Syria, for example. My point is that we should take no comfort from growing tension between Iran and its proxies on the one hand and radical Sunni Islamists on the other.