While the renewed fighting between the U.S. and Iran may appear to be evidence that diplomacy has failed, the constraints facing both governments seem to point toward yet another agreement in the near future. It’s simply a matter of how much damage the U.S. does to Iran and Tehran does to its regional neighbors before that deal is made.
In short, the dynamics are this: Iran cannot force the United States out of the Middle East, nor can it defeat American forces conventionally.