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. However, Pakistan actually has a history of nuclear proliferation and is the nuclear power most likely to fall to terrorist groups, yet India and Pakistan both have genuine needs for nuclear deterrence.
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.
Iran wants a glow in the dark missile
Iran won’t get the first Islamic bomb but it would like the first Shia bomb, unlike Pakistan there is no one that needs deterring. Russia and Pakistan have no interest in nuking Iran, nor does the US and West. Israel’s nuclear program has primarily been to deter an all-out land invasion and now to deter Iran but it too has no desire to attack Iran nor does any nation with nuclear weapons desire to attack Iran. The only reason to nuke Iran is if Tehran gets nuclear weapons because the actual nuclear doctrine, lampooned in Dr. Strangelove, states that an aggressive nuclear power must be pre-emptively struck in order to prevent a nuclear attack. Meaning, without a second strike capacity there is no way a nuclear power like Iran can survive a nuclear strike therefore Tehran must strike first in the hopes of eliminating its target or lose its nuclear weapons in a mushroom cloud. Launch or lose it. The result is, allied powers would have every reason to attack Iran once it goes nuclear but not before and since Iran is pretty much impossible to invade for any length of time, there is no alternative to using nuclear weapons to take out a developed Iranian nuclear arsenal.
The only purpose of an Iranian weapon is cover for aggression, the Soviets had and now Russia to some extent carry an implied threat when it invades territory but Soviet Russia never threatened a nation with nuclear weapons except as deterrent against nuclear weapons and Russia has never threatened any nation regarding nukes other than to have a renewed arms race with the US. The world has never seen a nation that exports terror use nuclear weapons -- at least a cover for ground military actions and perhaps as a weapon for a battlefield.
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. Nothing is being done about the rockets and missiles what will deliver a nuclear payload an area where Iran needs more development. Will the development of an Iranian missile system for its nukes be paid for by a delay in Iranian nuclear bomb production? Iran will be no Pakistan.