Many people are saying that the potential Iranian nuclear threat is exaggerated. These people have suggested that even if Iran were to acquire nuclear weapons, they could never use them because of the MAD (mutually assured destruction) principle. They couldn't be more wrong. Obviously, it is unlikely that the Iranians would fire nuclear-tipped missiles directly from Iran at targets in Israel or the US. However, there are two very realistic scenarios in which a nuclear war could still be started.
The scenario probably on most Americans' minds is one in which the Iranians pass off nuclear weapons to terrorists. In one scenario, the fanatical Iranian leadership could directly arm Hezbollah or some other group. Alternatively, a group of senior Iranian military commanders might act unilaterally to steal a nuclear weapon and pass it off to a terrorist group. The terrorists then float the nuclear weapon into Tel Aviv harbor, detonate, and kill hundreds of thousands of people. Nuclear-armed Israel responds. WW3 begins.
Even if you believe that the Iranian government wouldn't be so foolish as to pass off nukes to terrorists, or that nukes are impossible to steal, there is still serious risk of nuclear war if Iran gets nuclear weapons. That risk comes from the potential failure of MAD to deter a nuclear war. It is true that MAD saved us from war with the Soviet Union. Two points are noteworthy here.
1) To function properly, MAD requires that both sides of the prospective war be rational and deterrable. Can we expect a fanatical theocratic government to behave as rationally as an atheistic communist government?
2) MAD almost failed to prevent war between the US and USSR on multiple occasions. Read about Stanislav Petrov and Vasili Arkhipov. Both of these men were Soviet military commanders that single-handedly prevented WW3. Now imagine a hypothetical scenario. Replace both of these men with highly religious Iranian commanders. Instead of the USA being the enemy, make it Israel. Do you still have faith that MAD will work to prevent nuclear war?
As I recently wrote, military force against Iran still is not a good option. However, people need to recognize the Iranian threat and take it very seriously. We must not fall into the trap of thinking that just because the Iraqi threat was exaggerated, the Iranian one is too. Iran needs to be internationally isolated and closely watched until it gives up its nuclear ambitions.