The view among Mr. Bush’s top advisers, recalled Michael V. Hayden, then director of the Central Intelligence Agency, was that a strike “would drive them to do what we were trying to prevent.”

Those who warn against attacking Iran say that such a move would free officials in Tehran of many constraints. An attack, for instance, would all but certainly lead to the expulsion of international inspectors, which, in turn, would allow the government to undo hundreds of monitoring devices and safeguards, including seals on underground storage units. Further, an Iran permitted to present itself to the world as the victim of an attack would receive sympathy and perhaps vital imports from nations that once backed trade bans. The thinking also goes that a strike would allow Iran to further direct its economy to military ends.

Perhaps most notably, an attack could unite what is now a fractious state, these analysts say, and build an atmosphere of mobilizing rage. As the foreign ministers of Sweden and Finland wrote earlier this year, “It’s difficult to see a single action more likely to drive Iran into taking the final decision.”

History, the analysts say, demonstrates that airstrikes and military threats often result in unbending resolve among the beleaguered to do whatever it takes to acquire nuclear arms.

“People always assume the bad guys want nukes,” says Jeffrey Lewis, a nuclear nonproliferation specialist at the Monterey Institute of International Studies. “But I think there’s usually a hesitation about the balance of risk. My sense is that the threat of military action makes bad guys feel like they need the bomb.”