Suppose there was an explosion at an Iranian nuclear facility, missile base or warhead assembly plant. The explosion turns out to be a "dirty explosion" which scatters high purity nuclear weapon isotopes in the vicinity - say 99% Pu-239 which is pretty much undeniably weapon material. A mini Chernobyl or Three Mile Island ensues. The world community has a smoking gun with which to condemn the Iranian nuclear programme as military in nature all along. Significant urgency comes about if it appears that the Iranian nuclear programme was further along than known and that the Iranians were well on their way to putting a plutonium warhead on a missile. Also, due to the environmental, real estate and health damage caused by the dirty explosion, a significant public backlash in Iran occurs against nuclear power, possibly to the extent of declaring themselves a non-nuclear (civilian or otherwise) state. As we know Germany said "nein" to nuclear after the Fukushima disaster. I do not see how it will be possible to avert war otherwise. For the Iranian leadership to back down now would significantly diminish their prestige among the rank and file citizens; judging by the Arab spring they will be keen to not give cause for showing weakness. And of course Israel, the West and the Arabs can't tolerate Iranian nuclear weapons. What do you folks think?