There is another, less sanguine theory, that Iran will persist in its drive to achieve a bomb—or at least a break-out capacity to get one quickly if it so desired. The Iranians say they never trusted Mr Obama’s offer of detente early in his presidency because of the heavier sanctions and the campaigns of sabotage and assassination that accompanied the offer. In the same vein, they deplore the American administration’s recent decision to drop its longstanding classification of the exiled People’s Mujahedeen of Iran as a terrorist organisation. So Iran’s rulers will not easily trust future pledges to lift sanctions in return for nuclear concessions. In any event, Iran’s leaders may now believe that such concessions would destroy the Islamic Republic’s credibility and open it to a recurrence of the unrest that followed Mr Ahmadinejad’s disputed re-election in 2009. So it is possible that an American policy of containment, even an undeclared one, might lead to a long campaign of attrition of the kind that impoverished Iraq in the 1990s, while leaving its leader in power.