Before attacking Iraq in March 2003, the United States told the world that Saddam Hussein had reconstituted his nuclear weapons program in defiance of the United Nations. That claim, used to justify the war, was based on assessments provided by the United States intelligence community. But as everyone now knows, those assessments were wrong. So Jeffrey T. Richelson's history of American nuclear intelligence, including our attempts to learn about Iraq's nuclear program, could hardly be more timely.

In "Spying on the Bomb," Richelson, the author of several books on American intelligence, has brought together a huge amount of information about Washington's efforts to track the nuclear weapons projects of other countries. He examines the nuclear projects of Nazi Germany, the Soviet Union, China, France, Israel, India, South Africa, Taiwan, Libya, Pakistan, Iran and North Korea, as well as Iraq. Through interviews and declassified documents as well as secondary works, he sets out briefly what we currently know about those projects and compares that with assessments of the time.

This may sound like heavy going, but Richelson writes with admirable clarity. And along the way he has fascinating stories to tell: about plans to assassinate the German physicist Werner Heisenberg during World War II; about discussions in the Kennedy and Johnson administrations on the possibility of attacking Chinese nuclear installations; about Indian measures to evade the gaze of American reconnaissance satellites; and about the bureaucratic infighting over the estimates on Iraq.

The United States has put an enormous effort into gathering information about the nuclear projects of other countries. After World War II it equipped aircraft with special filters to pick up radioactive debris from nuclear tests for isotopic analysis. It created a network of stations around the world to register the seismic effects of nuclear explosions. Most important, in 1960 it began to launch reconnaissance satellites that could take detailed photographs of nuclear sites in the Soviet Union and China. Richelson occasionally speculates about the role of communications intercepts and of spies, but these appear from his account to have been much less important than the other methods of collecting information.

Through these means the United States has gathered a vast quantity of data, sometimes to surprising effect. Intelligence played a crucial role in the cold war, for instance, by reducing uncertainty about Soviet nuclear forces. Alongside such successes, however, there have been failures. One notable example concerned the first Soviet test, which took place in August 1949, much sooner than the C.I.A. had predicted. Another was the failure to detect Indian preparations for tests in May 1998, even though at an earlier time the United States, with the help of satellite intelligence, had managed to learn about preparations the Indians were making and to head off their tests.

But the most serious failure of all was in Iraq in 2003, because in no other case did the intelligence assessments serve as justification for the use of military force. The information needed for avoiding political surprise is one thing. That needed for preventive war is quite another, if only because of the consequences of making a mistake.

Beyond making the uncontroversial recommendation that "aggressive and inventive intelligence collection and analysis" should continue, Richelson draws no general conclusions. That is a pity, because his rich material points to issues that cry out for further analysis. He suggests in one or two cases that failures sprang from the mind-set of the intelligence community, but he does not elaborate on this point. He has little to say about relations between policy makers and the intelligence community, even though the quality of intelligence and the use made of it depend heavily on that relationship.

His focus is no less narrow in his discussion of foreign nuclear projects. He concentrates on the programs themselves, paying very little attention to their political context. Does that reflect a technological bias in nuclear intelligence? Would, for example, the prewar assessment of Iraqi nuclear capabilities have been more accurate if it had paid more attention to the broader political and economic circumstances of Hussein's regime?

The task of intelligence has become more complex than it was during the cold war. A single dominant nuclear opponent has now been replaced by a number of nuclear states, along with states and stateless terrorists that are aiming to get their hands on nuclear weapons. Meanwhile, the technology needed for producing nuclear weapons has become easier to acquire.

Many critics believe the recent performance of the intelligence community shows it has not responded adequately to this new situation. Richelson does not have much to say on this question; nor does he discuss the likely impact of the current reforms, initiated in response to the Iraq war, on the quality of intelligence. His reticence may imply that he does not think reform is necessary. Still, it is disappointing that he does not draw on his historical survey to discuss whether new approaches are needed for dealing with nuclear threats, and, if so, what those new approaches might be.

The nuclear deal reached during President Bush's recent visit to India unleashed a predictable wave of criticism. From editorial and op-ed pages to Congress, led by the left but supported on the right, the administration has been assailed for making a bad bargain.

Under the agreement, which still needs congressional approval, India would open much of its nuclear facilities to international inspections in return for gaining access to the world's supplies of uranium and U.S. nuclear expertise.

The attacks on the deal reflect the view of the nonproliferation lobby -- the experts and policymakers whose central concern is to stop the spread of nuclear weapons. I share their aim. But American arguments against the India deal are misleading and only expose the deep contradictions, if not hypocrisy, of our own nuclear policies.

There are two main criticisms of the agreement: first, it undermines the Nuclear Nonproliferation Treaty, the NPT, and second, it permits, even encourages, India to expand its nuclear weapons production.

The NPT issue is particularly sensitive at a time when the international community is trying to persuade Iran to give up certain nuclear technologies which many nations fear are part of a secret bomb program.

The NPT created two sets of global rules -- one for the five nuclear weapons powers it recognizes (China, the United States, Russia, Britain and France) and another for everyone else. The five, for example, allow only "voluntary'' international safeguards on their civilian nuclear facilities. They have no obligation to open their military programs to any kind of scrutiny. And the NPT places no real limits on their arsenals, other than a vague commitment to reduce and eventually eliminate all nuclear weapons.

The rest must open their nuclear energy programs fully to international inspection and agree never to build bombs. In exchange, they gain access to the peaceful uses of nuclear energy.

Iran -- and North Korea -- made that bargain and can be held to account for breaking the rules. But India consistently regarded that as an unequal trade-off and never signed the NPT; neither did Pakistan and Israel, two other nuclear weapons states.

India's nuclear program is the product of decades of largely indigenous effort; it did not result from secretive proliferation in violation of the NPT.

The deal with India turns the five into six. It treats India as a de facto member of the inner club. The deal would require changes in U.S. law to remove existing restrictions on the transfer of nuclear energy technology, changes that would allow India to be treated no differently from China.

That does not weaken the NPT -- it strengthens it. It brings it more into accord with reality and gives India a stake in a system it had previously rejected as unfair. It paves the way for India to join the Nuclear Suppliers Group, the international organization that controls nuclear exports.

The critics are right that the deal enables India to expand its production of fissile materials to make nuclear warheads. Eight of India's 22 power reactors will remain outside international controls, along with a new breeder reactor. The Indians fought for that exemption because they feel their nuclear arsenal may not be large enough to deter a nuclear first strike by Pakistan or China in the future. Critics fear that with increased access to uranium and limited inspections, India will set off an arms race in South Asia.

Again, the agreement simply treats India like the five. Nonproliferation experts claim that unlike India, however, the five have halted their production of plutonium and highly enriched uranium that could be used to build new weapons. This is true, but misleading.

The five have massive stockpiles of fissile material built up during the Cold War. "If I've got a full pantry, it's easy for me to swear off trips to the supermarket,'' said Michael Levi, an arms-control expert at the Council on Foreign Relations.

Moreover, the United States has embarked on a new program to rebuild its nuclear weapons production capability, including creating new facilities to produce plutonium cores for warheads and to assemble them.

India has agreed to back a global pact to cut off fissile-material production. But the Bush administration does not support a treaty that would actually verify this is taking place. And the U.S. Senate has refused to ratify the Comprehensive Test Ban Treaty that would permanently halt any new testing of nuclear weapons.

A Congress that can support those policies is hardly in a position to challenge the administration's agreement with India. Rather than block the U.S.-India deal, it makes more sense to improve it. This could include reaching agreements for cooperation between the two countries to ensure the safety and security of nuclear facilities, including those for military purposes, suggested Stanford Professor Scott D. Sagan, a leading expert on nuclear safety and nonproliferation. "Reducing the risk of terrorist theft of nuclear materials or weapons in India would also help protect the United States,'' argues Sagan.

Beyond that, the six acknowledged nuclear powers should begin to seriously fulfill their part of the NPT bargain -- to cap fissile-material production, to ban nuclear testing, and to eventually radically reduce stored arsenals of nuclear weapons and materials.

It is time to acknowledge that the international community's strategy on Zimbabwe has failed.

Robert G. Mugabe's regime has survived even as the economy deteriorates further (unemployment is above 70 percent, and gross domestic product will decline another 7 percent this year) and personal freedom suffers greater assaults (the recent "drive out the rubbish" campaign left 700,000 people homeless).

Indeed, with the opposition Movement for Democratic Change (MDC) on the verge of collapse - following a bitter fight over whether to boycott the recent Senate elections and after years of sustained government pressure - the regime has a stronger grasp on power than ever. Doddering though he may be, Mr. Mugabe, who recently turned 82, has foiled the pressure of the United States and Britain and the quiet diplomacy of his neighbors in southern Africa.

Predictions of imminent change still crop up in Western newspapers on the occasion of every new crisis in Zimbabwe. But these predictions have not come to bear, and they likely will not. So long as Mr. Mugabe reigns, his Zimbabwe African National Union-Patriotic Front (ZANU-PF) regime will survive.

The international community tried to change things. It embarked on a strategy of concerted economic and diplomatic pressure to weaken the Mugabe regime, trying to force it to either back down or submit to the democratic opposition. It's clear that strategy has failed.

It is, therefore, time to focus international attention on the prospect of Zimbabwe's only genuine political opening in the years ahead: the exit of Mr. Mugabe, whether through retirement or death, which will leave the regime internally and externally vulnerable.

Internally, the ZANU-PF regime without Mr. Mugabe at the helm will be uniquely susceptible in an election. In sub-Saharan Africa, opposition candidates have won post-transitional elections only 5 percent of the time against incumbents but 33 percent of the time against regimes' designated successors.

The most important reason for that is the incumbent's exit removes the regime's glue. The regime fractures into competing factions and is left with a substantially reduced capacity to repress the political opposition and rig an election.

In Kenya, after President Daniel T. arap Moi, and in Ghana, after President Jerry J. Rawlings, the regimes did not - could not - resort to all the dirty tactics that they certainly would have used had the incumbents run. In turn, these political openings have tended to galvanize the fractured opposition to successfully cooperate.

A ZANU-PF that is deeply unpopular, badly fractured among ethnic groups and between moderates and hard-liners (the expulsion of the information minister, Jonathan Moyo, is the beginning) and facing a reinvigorated opposition will not likely be able to effectively rig elections, let alone win the popular vote.

It will be critical, then, that presidential elections be held within a year of Mr. Mugabe's exit, before the regime has too much time to consolidate. If Mr. Mugabe's exit does not occur within that window before the 2008 elections, then international, and particularly regional, pressure will be crucial in forcing early elections.

Externally, Mr. Mugabe's exit may prompt genuine regional pressure. Analysts have long emphasized that international pressure requires the support of Zimbabwe's neighbors - especially South Africa - that have significant political and economic leverage. But to the great frustration of Western governments, southern African countries have thus far refused to publicly challenge Mr. Mugabe.

Their reluctance has much to do with Mr. Mugabe's status as a hero of Zimbabwe's anti-colonial struggle and a champion of liberation struggles elsewhere. Southern African nations will have much greater political room to apply real pressure on Zimbabwe when its leader lacks such credentials.

Simultaneously, the prospect of an altogether different level of violence might shake the complacency of southern African nations. Zimbabwe's implosion has not, thus far, been entirely bad for its neighbors. They have benefited from the elimination of economic competition and from the influx of professionals, and they have retained confidence that Mr. Mugabe can keep control.

But there is a real danger, if a post-Mugabe Zimbabwe is not handled adroitly, that elements of the opposition, disaffected war veterans and youth militia and losers in the ZANU-PF factional battle will take up arms and plunge Zimbabwe into civil war.

This specter should push neighboring countries to step up their efforts, especially to press the post-Mugabe regime to hold new presidential elections and encourage moderate elements within ZANU-PF.

Notwithstanding its occasional fulminations against Zimbabwe, the United States has failed in its efforts to unseat Mr. Mugabe's regime. The United States should focus now on his eventual exit by helping the MDC to overcome its bitter infighting and engaging Zimbabwe's neighbors, especially South Africa, in vigorous diplomacy, pushing them to prepare for the occasion.

The stakes could not be higher, for if the post-Mugabe period is the first genuine opportunity for political change in Zimbabwe, it may also be the last for some time.

"The United States is the most powerful since the Roman Empire," stated Stephen Walt, the Belfer Professor of International Affairs and academic dean of the John F. Kennedy School, Harvard University, delivering the 2005 Robert G. Wesson Lecture in International Relations Theory and Practice, at the Freeman Spogli Institute on November 16, 2005. America's unmatched power is therefore of great interest and concern to leaders in most other parts of the world, from President Putin in Russia, to President Chirac in France, and President Musharraf in Pakistan. For Americans, however, the key issue is how others are now responding to U.S. power.

Speaking before an audience of Stanford faculty, students, and the broader community, Professor Walt examined three interwoven themes: why other states do not welcome U.S. power; what are the main strategies available to them for dealing with American power? and what should the United States do in response?

As an integral part of his analysis, Walt showed opinion polls demonstrating a striking gap between American views of U.S. primacy and other countries' perceptions of the current U.S. role. For example, although the 2002 Pew Global Attitudes Project found that 79 percent of U.S. citizens believe it is good that "American ideas and customs are spreading around the world," and 70 percent think that U.S. foreign policy takes the interests of other states into account either "a great deal" or "a fair amount," overwhelming majorities overseas say the United States considers the interest of others "not much" or "not at all." Similarly, a 2005 BBC survey of 21 countries found only five, India, the Philippines, Poland, South Africa, and South Korea, where a majority of people had "positive" attitudes toward the United States.

There are three major sources of anti-Americanism, Walt explained. First, our sheer power makes other nations nervous. Second, there is a perceived sense of hypocrisy between our words and our actions. The case of nuclear weapons provides a vivid example. We preach nonproliferation, yet accord new respect and policy cooperation with newly nuclear states, such as India. Third, how the United States behaves in the world-what we do-invites antipathy. This latter point is abundantly clear in global opinion polls: Even in regions where anti-Americanism seems most strident, nations and individuals report that they do not object to our values or to what we stand for but rather to what we do.

Other nations, Walt pointed out, can choose a strategy of accommodation to our power or a strategy of resistance. Commonly adopted strategies of accommodation include 'bandwagoning," or realigning foreign policies with U.S. wishes, such as Libya's abandonment of nuclear weapons; "regional balancing"-using U.S. power to balance regional threats; "bonding" to curry favor with the United States; and "penetration," a strategy aimed at infiltrating the American political system to influence foreign policy outcomes.

In contrast, countries that choose to resist American power pursue five strategies:

"balancing" our power, alone or in alliance with others; "asymmetric responses," such as terrorism, which try to exploit specific areas of U.S. vulnerability; "blackmail," like North Korea's efforts to extract concessions from its nuclear weapons program; "balking," or tacit non-cooperation; and "delegitimizing," or attempts to turn others against the legitimacy of our actions or policies.

In light of the growing antipathy to U.S. primacy in so many parts of the world, Walt proposed three major courses of action to produce a more favorable response to U.S. power. First, he urged that we reduce American's military footprint abroad-and especially our ground force deployments-and return to a more traditional policy of regional balancing in cooperation with other nations. This policy would make greater use of American air and naval power and limit American intervention to cases where vital U.S. interests are threatened. Second, we should work harder to defend our international legitimacy and rebuild the U.S. image abroad, through a sustained campaign of public diplomacy and by keeping key American institutions-such as higher education-available to foreign visitors. Third, he advocated a more nuanced approach to America's traditional support for Israel, one that balances our genuine support for Israel's existence with the urgent need to bring a lasting settlement to the Israeli-Palestinian conflict.

"The more the United States uses its power in an overwhelming and capricious manner," Professor Walt warned, "the more the rest of the world will resist us." Conversely, the more the United States recognizes and respects the interests of others, while using its power to defend its own interests, the more other nations will welcome U.S. power. "The task we face," he advised, "is to rebuild the trust, admiration, and legitimacy the United States once enjoyed, so the rest of the world can focus not on taming U.S. power but on reaping the benefits it can bring."