A preventive strike against Iran, to prevent it from developing nuclear weapons, by either Israel or the United States would constitute an unjust war from both a Christian and a Jewish perspective.
Of course, this presumes that Iran would respond militarily to the strike, rather than passively accepting the damage, as did Syria in the wake of Israel’s preventive strike against Syria’s Osirak nuclear facility. If Iran did not respond militarily, the preventive strike would constitute a military action other than war
Iran seems much more likely than Syria to respond militarily. Iran is has more military might than does Syria, more wealth, and believes that it can control the Straits of Hormuz. Alternatively, Iran could respond short of war by stepping up its funding of anti-Israeli Palestinian terrorists.
A just war must meet all six criteria in the Christian Just War Theory tradition. First, the war must be to defend people or property. Although Iran has made threats, the threats have lacked follow-through. Possessing a weapon is not equivalent to using the weapon. Funding terrorists is not the same as declaring war, e.g., although the U.S. funded Afghan mujahidin fighting against the Soviets, both the Soviets and the U.S. recognized that the U.S. was not waging war on the U.S.S.R. In short, Iran having nuclear weapons does not constitute just cause.
Second, the war must be waged with right authority. Debate swirls as to whether right authority is national or international. In view of that debate, I’m willing to cede right authority.
Third, the war must be waged with right intent. The only right intent is progress toward peace. Starting an avoidable war is not progress toward peace.
Fourth, the war must have a reasonable chance of success. Strikes to destroy nuclear weapons’ development capacity are unlikely to succeed; the more likely outcome is to delay development rather than to preclude development of nuclear weapons. Furthermore, the measure of success is progress toward peace, not military victory. Even if Israel or the United States could permanently terminate Iran’s development of nuclear weapons, the enmity between Iran and ourselves would increase rather than diminish; the odds of war would have increased rather than diminished. In other words, military success is unlikely; progress toward peace is even more unlikely.
Fifth, the war must be proportional, i.e., the casualties the war causes must be fewer than the casualties doing nothing would have caused. This seems unlikely, but again I’m willing to cede the point that a preventive strike might cause fewer casualties. The number of casualties includes the total injured and killed on all sides; God values all lives equally.
Sixth and finally, the war must be a last resort. As I’ve repeatedly argued in this blog, Iran possessing nuclear weapons is not the end of the world. Iran has the same national aspirations and values as other nations; Iran has no desire for oblivion or nuclear winter. Iran and Israel could learn to co-exist with a policy of mutual assured destruction similar to the Cold War standoff between the U.S. and U.S.S.R.
In sum, from a Christian Just War Theory perspective, a preemptive attack on Iran to destroy Iran’s capacity to develop nuclear weapons satisfies no more than four, and probably none, of the six jus ad bellum criteria for assessing whether a potential war is morally just.
From a Jewish perspective, the only moral war is a defensive war. The two other Jewish ethical categories of war (the commanded and the optional) are no longer options. The rabbinical tradition is clear: the criteria for both commanded and optional wars entail impossible requirements or institutions that do not exist (e.g., direct revelation from God, the monarchy, and the Sanhedrin).
A preemptive strike on Iran is not defensive. Iran has not attacked Israel. In spite of bellicose rhetoric, Iran may never attack Israel.
Remember Saddam Hussein? He intended his bellicosity to impress others, even though his threats were empty, as the absence of weapons of mass destruction in post-conquest Iraq proved. Remember Khrushchev? He promised to destroy the U.S., but the U.S.S.R. in spite of repeated threats never attacked and eventually collapsed.
Not all threats are empty. But nations wisely respond to actions rather than to words. Otherwise, the world would have far more wars than it does. Being just, seeking to live in a manner faithful to God, involves risk and trust. Peace requires living with the possibility of war because the only option to peace is war, which is certainly evil.