Kenneth Pollack believes that “by any standards, the Iranian regime is odious. It is oppressive.It is authoritarian.” He is convinced that the world, the Middle East and the people of Iran would be better off if the regime were gone. He believes as well that Iran is intent on attaining a nuclear weapons capability. And he fears that the choices available to the United States and Israel have narrowed to two, each of them fraught with danger: a war to prevent Iran from joining the nuclear club, or learning to live with that reality.In Unthinkable, Pollack – a senior fellow at the Brookings Institute, former CIA analyst, director of Persian Gulf affairs at the National Security Council, and the author of, among other books, The Persian Puzzle – examines the risks and rewards of virtually all the policy options. These options include variants on the “carrot and stick” approach, such as the economic sanctions that the United States and its allies are deploying; working with dissident groups in Iran to effect regime change; an Israeli – or American – military strike on Iran’s nuclear facilities; and an aggressive version of containment, the strategy he recommends.Informative, judicious, lucid, logical and persuasive, Unthinkable is easily the best book on this explosive issue.Although his primary focus is on US policy, Pollack provides a nuanced analysis of the role of Israel. Since 2002, he claims, Israeli leaders have been obsessed with Iran’s nuclear program, with Prime Minister Binyamin Netanyahu portraying it as, in Pollack’s words, “the four horsemen of the apocalypse rolled into one.”In contrast, the author indicates, public opinion polls reveal that only about 20 percent of Israelis think Iran would attack them with a nuclear weapon. At the same time, he points out that had Israel not repeatedly sounded the alarm, the world may well have focused on other matters and Iran “probably would have crossed the nuclear threshold long ago.”Sensitive to the fears of Israelis and their security needs, Pollack nonetheless does not believe a nuclear Iran constitutes an “existential threat” to Israel. Although Pakistan possesses about 100 nuclear weapons, he notes, India has thrived, recently posting high rates of economic growth. And he makes a compelling case that an Israeli strike, which would be operationally difficult to pull off and might not succeed, would spur Iran to rebuild; undermine the sanctions and inspections necessary to keep it from rebuilding; alienate the US, its allies, and Muslim nations in the region, including those that loathe Iran; and provoke “that which it is meant to prevent” – i.e., terrorism, rocket and conventionally armed missile attacks.According to Pollack, air strikes by the US are also likely to make matters worse.Given Iran’s technical know-how, bombing might, at best, delay a nuclear program by a year or two. It would almost certainly end international support for sanctions. And it carries a risk, “even a likelihood,” says the author, that Iran would retaliate by waging asymmetric campaigns (terrorism, cyberwarfare, missile and rocket attacks) that could trigger “an escalatory spiral” leading to a wider war and an American invasion of Iran. A president who orders air strikes that result in hundreds or thousands of deaths, Pollack claims, “will have a difficult time halting operations short of Iran’s full capitulation (at least on the nuclear issue), regardless of the success or failure” of the initial operations.Meanwhile, an occupation of Iran, which has three times the population, four times the land mass, and much more oil than Iraq, “would be a major undertaking,” the author writes.Nonetheless, he thinks it would be “a huge mistake” for the US to publicly rule out the military option or support inside Iran for regime change. Fear of an American attack, he suggests, “has had a salutary effect” on Iranian behavior, “including helping to convince them that they shouldn’t weaponize, or at least should not weaponize yet.”He believes that under the circumstances, the most favorable scenario would involve an agreement in which the sanctions were lifted and in which Iran retained the right to enrich uranium, manufacture fuel for civilian reactors and keep a small stockpile of centrifuges; halted its programs short of deploying a nuclear arsenal; and accepted enhanced monitoring and inspection to reduce the likelihood that it could secretly “narrow its breakout window” (and weaponize).“So much better than the alternatives,” Pollack insists, this deal would require political leaders to tell voters that “it may be the best we can do, and that it is in our interest to take it rather than demanding a perfection that we can never attain unless we are willing to pay the costs of another major war.”Given the uncertainties, the author knows that he’s unlikely to persuade all of his readers to endorse a carrot-andstick approach over the Pandora’s box of air strikes and war. Unthinkable, however, has done the significant service of giving everyone interested in this vexing foreign policy challenge the tools to assess “the costs and risks as they are, not as we would like them to be.” The writer is the Thomas and Dorothy Litwin professor of American studies at Cornell University.