Illustration by Tom Bachtell

In the State of the Union address of 1954, which Dwight Eisenhower delivered less than a year after he had secretly ordered the C.I.A. to overthrow Tehran’s left-leaning government, he celebrated “the forces of stability and freedom” at work in Iran. In 1980, Jimmy Carter delivered his annual address amid the whirlwind of Iran’s Islamic and anti-American revolution, which was inflamed in part by Iranians’ memories of Eisenhower’s coup. “We will face these challenges,” Carter declared. “And we will not fail.” Three decades on, Iran’s theocrats have built a police state, spread violence across the Middle East, and acquired nuclear reactors. Iran remains a perennially grim subject of Presidential oratory, and last week Barack Obama, while delivering his third State of the Union, added another entry: “Let there be no doubt: America is determined to prevent Iran from getting a nuclear weapon, and I will take no options off the table to achieve that goal.”

Leaving options on the table is a not-so-oblique way of threatening war. On the same day, Israel’s Prime Minister, Benjamin Netanyahu, told the Knesset, “Only a combination of crippling sanctions and putting all the options on the table can make Iran stop” its nuclear drive. Meanwhile, three of the remaining candidates for the Republican Presidential nomination—Rick Santorum, Mitt Romney, and Newt Gingrich—have been speaking approvingly about bombing Iran’s atomic sites or assassinating its scientists.

There is reason to doubt, though, that an attack on Iran is imminent. The United States and the European Union are ratcheting up economic sanctions in the hope that they will push Iran’s President, Mahmoud Ahmadinejad, to re-start serious nuclear negotiations after a year’s hiatus. The E.U.’s twenty-seven member countries, which buy about a fifth of Iran’s oil exports, agreed last week to forgo all Iranian crude by July. Ahmadinejad said soon afterward that he would indeed be willing to talk again. The strategy, led by Obama, appears to be achieving its aim of raising the pressure on the ayatollahs to an unprecedented level. The value of Iran’s currency has fallen sharply. The diplomatic campaign would be stronger if it contained a definite plan to assuage Iran’s fears that the West and Israel ultimately seek regime change in Tehran—fears that presumably inform Iran’s search for a nuclear deterrent. Yet this is a rare period of momentum and international unity regarding Iran. “A peaceful resolution . . . is still possible, and far better,” the President said in the State of the Union. An attack now by either Israel or the United States would shatter diplomacy’s achievements.

The Iranian nuclear program is a problem with a long arc. The secret work began in the late nineteen-seventies, under the secular-minded Shah returned to power by Eisenhower’s intervention. There can be little doubt that Iranian scientists have studied atomic-bomb design. Several leading Israeli defense officials have said recently that Iran’s nuclear work has become so advanced that unless the sites are bombed soon—within months or, at most, within a year—it will be too late to prevent the country’s acquisition of atomic arms. It is difficult to tell whether the officials really believe that or if they are just adding to the pressure on Tehran. Either way, the evidence casts doubt on their judgment. The centrifuge technology that Iran has acquired to enrich uranium is relatively easy to hide, so it is conceivable that work has advanced further than world governments understand. But all of Iran’s known nuclear-fuel enrichment facilities are today under U.N. monitoring, and there is no evidence that any of Iran’s enriched uranium has been diverted to a military program.

Short of a nation conducting a bomb test, it’s not possible to define precisely when a country’s technology has attained weapons capability. Even if Iran is determined to stage a test, it is not certain how fast it will be able to do so. Its nuclear program has taken periodic leaps forward, but has also been marked by pauses and technical failures. Some of the failures have likely been caused by sabotage carried out covertly by the United States and Israel, including the unleashing of a computer virus called Stuxnet, which infected Iranian centrifuge controls. Meir Dagan, who through 2010 ran Mossad, Israel’s external intelligence service, has said that he does not think that Iran can deploy a weapon before 2015. Last February, Lieutenant General James Clapper, the director of National Intelligence, testified to Congress that Iran could technically produce enough material for an atomic bomb “in the next few years,” but that the U.S. intelligence community “did not know . . . if Iran will eventually decide to build nuclear weapons.”

The burden of proof rests, in any event, with those who would urge war. Two of Iran’s uranium-enrichment sites are underground; there are two significant reactors and another being built, and possibly other important sites that are unknown. In these circumstances, no one can confidently predict what aerial bombardment would achieve by way of damage or delay to Iran’s over-all nuclear timelines. And the costs of any such attack are much easier to describe than the benefits. For Israel, those costs would certainly include heavy retaliatory rocket and missile strikes by Hezbollah and Hamas against Israeli civilians, a wave of popular anti-Israeli upheaval in Egypt, and the prolonged inflammation of Iran’s nuclear nationalism. A regional war involving Lebanon, Syria, and oil-producing Gulf emirates would also be a possibility.

Moreover, although “the forces of stability and freedom” may be elusive and late arriving in Tehran, the durability of the Islamic Republic is far from assured. In Cairo last week, Egyptians gathered in Tahrir Square to commemorate the first anniversary of their revolution, an uprising that was as stunning and as unforeseen as Iran’s revolution was in 1979. The Arab Spring offers ample evidence that no dictatorship should be assumed to be indelible.

In 2009, in Prague, Obama, in one of the eloquent and idealistic speeches that characterized his early Presidency, pledged to pursue a world free from the menace of nuclear arms. He receives little credit for his work in this field, but he has delivered: accelerated programs to safeguard loose nuclear materials abroad, and a hard-won New START treaty with Russia, which proposes a smaller American nuclear arsenal. Iran’s case doesn’t offer much prospect for clear achievement; it is a crucible of uncertainty and risk. In Prague, however, Obama warned against “fatalism” about the nuclear danger, and he prescribed a strategy to defeat it: “Patience and persistence.” That strategy shouldn’t be taken off the table. ♦