In 1998 when Iran and India announced they had gone nuclear within weeks of each other and followed with tests, the world went into a Chicken Little frenzy and decided there would be nuclear winter in South Asia. The fears were understandable, Pakistan had the world’s first “Islamic Bomb” just the kind of wobbly, unpredictable state that should never have such a weapon. India was little better as it seemed both nations who have known great hostilities over border disputes could easily engage in an irrational nuclear war. However, the reason for India’s weapons was not just to deter a Pakistan who might not have developed a nuclear program had India not been determined to have one. India needed a credible deterrent against China and naturally China to some unknown degree probably favors the Pakistani program.
Since 1998 both nations have for the most part had better intergovernmental relations although terrorism remains a problem stemming from Pakistan, these problems have not escalated into a prolonged conflict or raised the specter of nuclear war. Both nations seem to embrace the concept of MAD and do not wish to destroy themselves in destroying each other. More worrisome are countries like Pakistan developing nuclear weapons, nothing is more dangerous than creaky dictatorships developing nuclear weapons. Even if Pakistan never again becomes a problem, eventually an irresponsible nation will use these weapons. Why that nation is not Pakistan is nuclear weapons serve no aggressive purpose. If Pakistan launches against any nation it will be destroyed by a fearful India.
Is Iran’s aggressive desire for a weapon worse than Pakistan’s instability? The short answer is “yes” unless Pakistan falls to the Islamic State. if Pakistan actually falls. There may be little difference between an Islamic State nuclear program and an Iranian one except that Iran has demonstrated it can methodical and patient in building leverage to gain territory. Pakistan’s purpose in having nukes is ultimately defensive, while there are many reasons to be mistrustful of Pakistani security there is little reason to fear a nuclear launch by any recent government that has controlled Pakistan. Iran by contrast has no rationale for a nuclear weapon other than aggression, it also a theocracy under the rule of a supreme leader which means an Iranian nuclear weapons system would always be an unpredictable problem for the region. An arms race has already begun with Egypt, Saudi Arabia and Turkey stating that they will begin nuclear research. So, there are very good reasons to prevent Iran from getting a nuclear weapon but a large bomb is only part of the equation there other part is delivery. So far the nuclear agreement only limits itself to nuclear development but the Iranians are already very near a bomb.