To address their core, external security concerns, several Arab Gulf states, with the help of the United States and other Western nations, have focused on maintaining their qualitative military edge over Iran, their main adversary, and putting a premium on defense and deterrence.

This includes erecting an integrated regional missile defense structure (a far from complete project whose importance was reiterated at the US-GCC summits in Camp David in May 2015 and Riyadh in April of this year) to defend against potential Iranian missile and rocket attacks; developing and purchasing modern and capable naval and land forces to counter and interdict potential Iranian ground and sea operations and weapons shipments, respectively; and acquiring stealth and powerful aircraft to protect and maintain supremacy in the skies.

However, one notable military capability in which the Arab Gulf states have chosen not to make serious investments to boost their conventional military deterrent against Iran is an offensive ballistic missile force (although they have made some advances, particularly in the UAE's case, in long-range artillery rockets). This has created somewhat of a deficit in the GCC force mix, the consequences of which are unclear.

Imbalanced defense postures are prevalent around the world. Indeed, they are the norm rather than the exception, given the reality of constrained defense budgets and the impossibility of perfect defense. While all nations strive for more balanced defense postures, most are forced to make tough compromises in their defense planning. As always, the challenge is to pursue the right tradeoffs, depending on the threat spectrum and national defense needs.

For decades, the United States government and various private US defense firms have counseled the Arab Gulf states on the most effective military posture. Washington has advised Arab Gulf capitals to forgo the development of an offensive missile force, even one that might aid deterrence goals, for four main reasons.

First, the United States continues to have a strategic interest in preventing an offensive missile race in the Middle East whose fires could harm Israeli security significantly and depending on weapons ranges, reach the West.

Second, the introduction of US or Western offensive missiles into the military balance in the Middle East almost automatically brings Russian and Chinese capabilities into the mix, which goes against US strategic interests.

Third, it is not at all clear that the Arab Gulf states' possession of ballistic missiles would augment their military deterrent against Iran. It could even have the opposite effect. Given Iran's extra sensitivity to missiles as a result of its horrible experience with Iraq during the 1980-1988 war, it might launch preemptive strikes to eliminate the threat. Doing so wouldn't be incredibly difficult because stationary offensive missiles are especially vulnerable when deployed in constrained geographies such as in the smaller Arab Gulf states, where military assets are already condensed and cannot be further dispersed (the hardening of missile silos can reduce but not eliminate vulnerabilities).

Fourth, relinquishing the offensive missile option helps America's regional partners project an image of peaceful nations who prioritize stabilizing weapons over destabilizing weapons, and defense over offense.

The picture in Iran's case is almost completely reversed. While Iran has sought to upgrade its air defense capabilities with the potential acquisition of modern Russian systems, its strategic priority has always been to develop its offensive missile arsenal and long-range artillery rockets, which can be used to strike anywhere in the Gulf and the Levant, and in peace time, is meant primarily to deter Israel and coerce its Gulf neighbors.

The chances of a direct and sustained Iran-GCC conventional military encounter that would escalate to a powerful kinetic exchange are minimal in the presence of a major, forward deployed US and British military deterrent. But should there be any uncertainty about US and/or British military readiness in the region, and an accident take place, swift but heavy Iranian bombardment of critical civilian installations in, for example, Abu Dhabi, Manama, or Riyadh would be highly destructive given these countries' lack of strategic depth and the concentration of political power and civilian leadership in a few locations. Instead of engaging in force-on-force warfare, Iran would most likely aim its first, and possibly only, shots at key GCC vulnerabilities and hope to get lucky (its missiles lack precision) before Washington and London intervene. It is not that Iran is immune to strategic attacks itself, but the killing of Supreme Leader Ayatollah Ali Khamenei, for example, would not necessarily lead to the death or collapse of the Islamic Republic.

Looking ahead, in a likely era of decreased US military involvement in the Middle East, increased involvement of Russia and China, and a greater drive for autonomy in security thinking and practices on the part of the Arab Gulf states, it is worth debating how America's regional partners might tweak their defense strategies and postures in the future, away from US preferences. Furthermore, should missile defense prove too costly in an age of financial retrenchment and too unpredictable or ineffective in a military environment of Iranian missile proliferation and advancement, some Arab Gulf states might reconsider their strategic defense and deterrence options and opt for the development of an offensive missile force, possibly mounted on destroyer ships or military vehicles (safety comes from mobility) to counterbalance Iranian superiority in that domain. Saudi Arabia would not have to start from scratch, given its possession since 1987 of an unspecified but likely small amount of medium-range Chinese ballistic missiles, which it paraded for the first time in 2014 to possibly put Iran on notice or send a message to Washington of displeasure with US policy and increased Saudi security assertiveness.

Many might find these potential military scenarios unrealistic given the United States' large and robust posture in the Gulf, which in itself should continue to make Iran think twice before crossing any red lines (at least in the conventional domain). But (mis)perceptions of US retreat in Tehran and Gulf capitals are rampant, which could lead states in the region to pursue courses of action that were deemed unthinkable in the past.

Bilal Y. Saab is Senior Fellow and Director of the Middle East Peace and Security Initiative at the Brent Scowcroft Center on International Security at the Atlantic Council, where he chairs the Gulf Policy Working Group.

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