The closest things we have to consensus views on the likelihood of war breaking out with Iran rate such a war as unlikely in the near term, in the sense of a less-than-even chance. The most recent (i.e., last month) iteration of a poll of twenty-two experts done for The Atlantic (I am one of the “experts”) yielded an average probability for either the United States or Israel attacking Iran in the next year of 36 percent. Turning to those who put their money where their prognostications are, participants in the online prediction market Intrade currently rate the chance of a U.S. or Israeli airstrike against Iran sometime before the end of 2012 as about 33 percent. The most likely outcome of a situation, however, is not the only outcome we should worry about, and we should especially worry about outcomes that, although less likely, would be especially damaging to our interests. A former vice president of the United States once said that even if there were only a 1 percent chance of a really bad thing happening, we need to work to prevent it from happening. He was wrong in his dismissive approach toward probabilities. But the 33–36 percent range represents far more likelihood than 1 percent, and war with Iran would be a really bad thing for the United States.
The current danger of a war derives from a mix of factors that could slide Iran and the United States toward combat even if senior decision makers in neither Washington nor Tehran want a war. (These factors no doubt underlie a significant increase this month in the likelihood of war as measured by the Intrade market, which in late June had dropped below 20 percent.) One factor is the combination of Western economic warfare against Iran in the name of getting Iran to make concessions on its nuclear program, combined with the failure of the West, despite its stated objective, to use its economic sanctions as leverage to accomplish that very goal. The result is an impression of stalemate leading promoters of a war to pronounce that “diplomacy has failed.”
Another factor is the chance of of an accidental altercation involving U.S. and Iranian forces in the Persian Gulf. That chance increases as the United States beefs up its naval forces in the Gulf with an additional aircraft carrier and conducts additional exercises there. U.S. naval officers have reported that insofar as they have communications with Iranian counterparts at sea, the latter appear to behave professionally and do not seem to be looking for a confrontation. But the more military activity there is in the area, the greater is the risk of an incident that stems from nervousness or faulty communication (or even intentional action by a hot-headed low-level Revolutionary Guard commander) and then spins out of control.
A reminder of how faulty communication and nervousness on the U.S. side can produce an incident was the firing by the U.S. Navy at an Indian fishing boat earlier this week off the coast of the United Arab Emirates. This incident also recalls the one in 1988 in which the crew of another U.S. warship in the Persian Gulf, also mistakenly imputing hostile intentions, shot down a civilian Iranian airliner. That tragedy killed 290 persons and led Iranians to conclude that it was an intentional act by the United States. The casualties in this week's incident were limited to one Indian fisherman killed and three wounded, but if an Iranian vessel had been involved the chance of escalation would have been significant.