The more realistic scenario is Mossad sneaking a small, dirty nuc into Iran and detonating it at a remote region. Very few are killed, small so radioactivity has very limited impact. The international community comes unglued and complete demand that Iran be subject to outside inspection and removal of weapons. Obviously Iran is too risky to be trusted with weapons, they cannot even manufacture them in safe mode. Even Russis and China would have to concede. They would be disarmed with near 100% agreement. No actual shooting war takes place.
At least this is how I would do it.
Boo