Collapse of the agreement will not necessarily lead to war

With or without the support of the international community, however, if there is no agreement, then the main restraint on Iranian breakout would have to be U.S. and partner intelligence collection and U.S. readiness, understood by all, to use force if Iran approaches a nuclear weapons capability. While that is stated U.S. policy, albeit expressed indirectly such as "preserve all options," the president has effectively undercut this policy by repeated warnings about inevitable "war" if no agreement is reached. Without an agreement a military confrontation would be more likely, but not inevitable. Of course, a military confrontation with Iran could be costly and risk escalation, but, absent spectacularly bad U.S. decisions, it is unlikely to produce either a U.S. defeat or a "war" in the sense normally used in American political debate -- endless, bloody ground combat by hundreds of thousands of troops as in Iraq or Vietnam. Based on my experience I know how uncertain any resort to force is, but all our security interests are ultimately anchored on willingness to use force, and success doing so.