In practice, deterring a nuclear Iran means extending the US nuclear umbrella and pledging to fight nuclear wars on behalf of America’s regional partners. But, is the US really willing to trade New York for Riyadh?
To make this inherently incredible threat credible, the US would have to station troops and forward-deployed nuclear weapons in the region, ensuring that the United States will be dragged into any future conflict. These and other costly measures would have to remain in place as long as Iran exists as a state and has nuclear weapons, which could be decades or longer.
And, while the threat of US retaliation could deter Iran from intentionally launching a nuclear war, the threat to go to war with a nuclear-armed Iran – especially after America was unwilling to fight a nonnuclear Iran – would be irrelevant or incredible as a response to other Iranian challenges. That means the US would simply have to live with those other challenges.