“If the United States were to decide that to garner greater international support, galvanize U.S. domestic support, and/or provide a legal justification for an invasion, it would be best to wait for an Iranian provocation, then the time frame for an invasion might stretch out indefinitely. With only one real exception, since the 1978 revolution, the Islamic Republic has never willingly provoked an American military response, although it certainly has taken actions that could have done so if Washington had been looking for a fight.
Thus it is not impossible that Tehran might take some action that would justify an American invasion and it is certainly the case that if Washington sought such a provocation, it could take actions that might make it more likely that Tehran would do so (although being too obvious about this could nullify the provocation). However, since it would be up to Iran to make the provocative move, which Iran has been wary of doing most times in the past, the United States would never know for sure when it would get the requisite Iranian provocation. In fact, it might never come at all.”