In the Iran-Israel scenario, a nascent attacking force lacking countermeasures faces a missile defense system that has been under development for 25 years and that is now receiving third-generation equipment, probably including classified capabilities. Iranian uncertainty will be compounded by the potential for unconventional defensive techniques, including cyberattacks. Israel's ongoing civil defense efforts have been recently upgraded.
From the viewpoint of Iranian leaders, there can be no worse scenario than an attempted nuclear strike that fails to destroy Israel as it exists today. Israel could be seen as justified in threatening any use of its forces—including nuclear—to compel Iran to take steps to ensure that such actions would never be repeated, up to and including regime change and the surrender of existing leaders to international tribunals. Iran also could expect no support from its Sunni neighbors.
It is impossible to say when Iran would be able to guarantee an effective nuclear attack—a regional form of mutual assured destruction—if only because the equation involves Iran's confidence in its own assessment of Israel's defensive capabilities in all regimes. (That confidence cannot be at a high level, following cyberattacks and assassinations of nuclear researchers.)
The situation makes more sense in the light of other potential motivations—reasons why, to paraphrase Hamre, Iranian leadership might view nuclear weapons as useful.
Iran's conventional armed forces are weak relative not only to those of Israel, but to those of the Sunni Arab States to the south—something that is apparent to any Iranian with access to the Internet, government propaganda notwithstanding. However, by being seen as the first Islamic nation in the region to be close to acquiring nuclear weapons, Iran can appear strong.
The nuclear move has also driven the Israeli and U.S. governments to talk about military action. For governments embattled and criticized at home to magnify the threat from external enemies is not exactly unknown. At the same time, Iran's continued denials that it desires nuclear weapons allows its leaders to escape from the charge that they are warmongers.
On the other hand, a real Iranian bomb—even in the form of a handful of weapons and rudimentary delivery systems—could vastly complicate the tense military and political situation in the Gulf. At the same 2009 conference where Hamre spoke, Vice Adm. Robert Harward, then-deputy commander of U.S. Joint Forces Command, reported on a five-day Joint Operating Environment wargame held in November 2008. It reflected some probabilities: That rising nuclear powers might be willing to use tactical nuclear weapons, and that both state and non-state actors “would not view nuclear weapons as a first resort, but might not see them as a last resort.” The result: “The presence of nuclear weapons brought on operational paralysis.”
Distances from Iran to its targets are shorter in the Gulf, the Gulf nations' defenses are not as advanced as Israel's, and above all, those nations are not yet nuclear-armed. Whether they can readily use an Iranian bomb as a justification for going nuclear, without getting cut off from their Western conventional weapon supplies, is unknown.
In short, Iran's leaders can use a bomb—real or potential—to offset non-nuclear weakness, force other nations to treat their wars-by-proxy more diplomatically and generate an environment where its own people are willing to accept repression in the name of security.