With nuclear weapons, there is no effective defense. As a result, unless or until universal disarmament can be achieved, arming to prevent war can only mean nuclear deterrence. The US and the Soviet Union overdid deterrence by a large factor in my estimation, but the general view is that it seemed to work in that particular situation. The key assumption of nuclear deterrence is that the prospect of a single weapon dropped on a single city makes any war of conquest unattractive. Equally important is that the inevitable devastation was obvious to all ahead of time, so that the usual demagogic arguments for war failed and for the most part were not made.

No one pretends that what I have just said about nuclear deterrence is the whole story. For one thing, there are many traps and dangers in the actual practice of nuclear deterrence. What is to be done, for instance, about challenges that don't directly involve the risk of nuclear war but might do so down the line? There were plenty of such challenges during the Cold War, in Korea, in Berlin, in Cuba, and in Israel.

Russia's economy and political system have undergone enormous changes since the end of the Soviet era. A burgeoning market system has replaced the Soviet command economy, and open multiparty competition for representation in Russia's political institutions operates in place of the Communist Party that ruled the country exclusively for more than 60 years. In the areas of defense and security, however, radical changes to the organizational and operational system inherited from the Soviet Union have yet to occur. After more than a decade of reform efforts, Russia's armed forces have shrunk to less than two-thirds of their 1992 size of 3.7 million. Russia's military leaders, nevertheless, have been adamant about preserving Soviet-era force structures and strategic plans. Why have Russia's armed forces--nearly alone among the core institutions of the Russian state--resisted efforts to change their structure and character in accordance with institutional arrangements operative in Western liberal democracies?

The nuclear programs of the Democratic People's Republic of Korea (DPRK), Iran, and Pakistan provide the most visible manifestations of three broad and interrelated challenges to the nuclear nonproliferation regime. The first is so-called latent proliferation, in which a country adheres to, or at least for some time maintains a façade of adhering to, its formal obligations under the Nuclear Nonproliferation Treaty (NPT) while nevertheless developing the capabilities needed for a nuclear weapons program. That country can then either withdraw from the NPT and build actual weapons on short notice, or simply stay within the NPT while maintaining the latent capability for the rapid realization of nuclear weapons as a hedge against future threats. This was the path followed by the DPRK with its plutonium program and one that is likely being followed by Iran and more subtly by others. The second broad challenge is first-tier nuclear proliferation, in which technology or material sold or stolen from private companies or state nuclear programs assists nonnuclear weapons states in developing illegal nuclear weapons programs and delivery systems. The third challenge--the focus of this article--is second-tier nuclear proliferation, in which states in the developing world with varying technical capabilities trade among themselves to bolster one another's nuclear and strategic weapons efforts.

Opponents rarely go to war without thinking they can win--and clearly, one side must be wrong. This conundrum lies at the heart of the so-called "war puzzle": rational states should agree on their differences in power and thus not fight. But as Dominic Johnson argues in Overconfidence and War, states are no more rational than people, who are susceptible to exaggerated ideas of their own virtue, of their ability to control events, and of the future. By looking at this bias--called "positive illusions"--as it figures in evolutionary biology, psychology, and the politics of international conflict, this book offers compelling insights into why states wage war.

Johnson traces the effects of positive illusions on four turning points in twentieth-century history: two that erupted into war (World War I and Vietnam); and two that did not (the Munich crisis and the Cuban missile crisis). Examining the two wars, he shows how positive illusions have filtered into politics, causing leaders to overestimate themselves and underestimate their adversaries--and to resort to violence to settle a conflict against unreasonable odds. In the Munich and Cuban missile crises, he shows how lessening positive illusions may allow leaders to pursue peaceful solutions.

The human tendency toward overconfidence may have been favored by natural selection throughout our evolutionary history because of the advantages it conferred--heightening combat performance or improving one's ability to bluff an opponent. And yet, as this book suggests--and as the recent conflict in Iraq bears out--in the modern world the consequences of this evolutionary legacy are potentially deadly.

This article grew out of a week-long study in August 2002 to assist ongoing efforts inside and outside the government to remedy some vulnerabilities of the international shipping system on which US and a great deal of world prosperity depend. The study's objective was to identify the most important research initiatives and the major policy issues that need to be addressed in order to improve security of imports using shipping containers, particularly against the importation of nuclear materials and weapons, while maintaining an open trading system. To be effective, a system to detect nuclear weapons or special nuclear material before they reach U.S. ports must be international in scope and reach. It must also be economically acceptable both in terms of total cost and with respect to how these costs are allocated; degrade gracefully when subjected to attack; produce actionable intelligence in a timely manner; treat false alarms realistically; be adaptable to a variety of local physical and political conditions; be auditable, secure yet accessible to the needed foreign and domestic security agencies, and have clear lines of oversight and responsibility. Finally, the system should be flexible enough to allow for regular updates as users and operators gain experience and system performance is reviewed. This study identified a sample technical approach that is feasible technically and operationally and involves components already in the early deployment stage. The approach involves container certification; monitoring at ports of embarkation, debarkation, and continuously during shipment and storage; and continuous data fusion. Specific recommendations regarding system characteristics made by the study include rigorous testing during deployment and in the field, international coordination of standards and protocols, careful analysis of the system for compatibility with pertinent governmental policies and business and labor agreements, and early provision for forward-looking research and development.