When it comes to cutting a deal with Iran over its nuclear program, the biggest fear is: what if the mullahs cheat?  Hawks have predicted that a nuclear Iran will become increasingly aggressive, compelling its neighbors to develop nuclear weapons of their own. Proliferation optimists have dismissed such talk by suggesting nuclear weapons will enhance the security of the regime and make it less, not more, aggressive, and that if Iran’s neighbors decide to join the nuclear club as well, so be it: the more the merrier.

But what if the proliferation optimists that dominate much of the academic thinking on the spread of nuclear weapons are wrong?  From it’s first days in office the Obama Administration has cut funding for missile defense and pulled interceptors back from Eastern Europe as part of a deal with Russia.  However, a theatre missile defense shield is the best way to mitigate the fallout from failed diplomacy by rendering nuclear bullying against American allies by Iran useless, and removing incentives for them to develop nukes of their own.  Missile defense would kill two bombs with one stone.

Current reports suggest that the Iranians are complying with their commitment under the First Step Agreement; an agreement is even in the works over the Arak reactor.  However, let’s accept for the moment that the skeptics’ fears are warranted: Khamanei and Co. are hell-bent on getting their hands on a nuclear weapon, and will either covertly cheat on any deal, or will wait until the sanctions have been reversed and use their newfound access to Western markets in order to finance an arsenal. Unlike enforcing territorial boundaries, the tricky thing about nuclear weapons programs is that states may develop them in secret, out of view of even the most intrusive inspectors.

Coupled with the so-called pivot to Asia and the Obama Administration’s failure to make good on it’s red lines, the prospect of a nuclear Iran has given many of America’s allies in the region an abandonment complex. These states fear that a nuclear Iran will use its arsenal to bully and dominate the region in the same way we once feared Saddham Hussein would, only this time they wouldn’t be able to rely on American support. Western decision-makers fear that proliferation will beget proliferation, leading states from Egypt to the Emirates, Jordan, and Saudi Arabia to pursue the bomb.

Some states have begun hedging their bets by investing in civilian nuclear industries that can be converted for weapons development.  The Saudis have hinted they are interested in being placed under Pakistan’s nuclear umbrella- a country with no shortage of mishaps and snafus with its own nuclear program.  The acquisition of a nuclear weapon would provide deterrence by punishment, where the basic point is if you kill my cat, I’ll kill your dog and just about every other animal on your farm.

However, it would take years for most of these states to develop nuclear weapons of their own.  Jacques Hymans of USC points out that developing states have a tendency to meddle in the professional scientific institutions responsible for bringing nuclear weapons from the drawing board to the battlefield.  Interventions of this sort needlessly delay states’ attempted journey across the atomic Rubicon while doing little to enhance their security.  These states would have the worst of both worlds: no defense against Iran and all the opprobrium that comes with pursuing the bomb.

In contrast to deterrence by punishment, missile defense would provide deterrence by denial, rendering attacks (and, therefore, threats to attack) useless.  Even if a nuclear Iran wanted to dominate the region, a workable theatre missile defense would render Iranian aggression pointless.  While nuclear bullying is rarely successful in the first place, potential Iranian targets under the protection of missile defense would be free to dismiss credible threats as though they were bluffs.  They could tell Tehran to go ahead and make their day.  This would also remove any justification these states would have for developing nuclear deterrents of their own.

From its first days in office, the Obama Administration has cut the budget for missile defense.  It also pulled interceptors back from Eastern Europe.  Yet, if the First Step Agreement fails, a missile defense shield may be the best hope for preventing a fiasco with Iran from turning into a regional catastrophe.