Rethinking N + 1.

• Author: Roberts, Brad
• Position: Proliferation of nuclear weapons - Includes related article on British politics

In April 1961, one of the seminal think-pieces on proliferation appeared. This was Albert Wohlstetter's famous Foreign Affairs article analyzing the so-called "N + 1" problem. This formulation was Wohlstetter's way of characterizing the next incremental addition to the existing number of nuclear weapons states. In an elegant analysis focused mainly on the nuclear problem in Europe, he argued that the U.S. nuclear umbrella was the answer to the security needs of NATO's potential next nuclear states. He argued further that disarmament would only fuel Soviet ambitions, but that export controls and modest arms control measures had a role to play in limiting nuclear diffusion.

In this, as in so many other areas, Wohlstetter's ideas helped to shape his generation's thinking about the proliferation problem. But wholly new factors have arisen over the past four decades, and we need to think differently about the issue because the problem itself has changed. We can best see how it has changed by taking separately the two parts of Wohlstetter's simple "N + 1" expression.

First is the "N" factor: the number of existing nuclear-armed states. Today, the policy debate remains focused on the challenge of preventing those two or three states most desirous of joining that number from achieving their ambition. Now, as then, nuclear proliferation presents risks of major importance for international stability and U.S. security. The emergence of a nuclear-armed Iraq, Iran, or North Korea would be deeply unsettling, both regionally and globally. So too would be the leakage of nuclear weapons materials, technology, or expertise to both state and nonstate actors. Stopping such proliferation remains a top policy priority, as it was in 1961.

But the nuclear dynamic is more complicated than suggested by "N + 1." There is also an "N - 1" phenomenon. The number of states opting out of the nuclear weapons business (South Africa, Ukraine, Belarus, Kazakhstan, Argentina, and Brazil) is roughly double the number working to get in. Moreover, the emergence since 1961 of de facto nuclear weapons states outside the superpower strategic framework (Israel, India, and Pakistan) has not so far changed the world in any fundamental sense, largely because their purposes are understood to be essentially defensive.

The proliferation phenomenon has been further complicated by the increased prominence of elements of the problem other than the nuclear one. Chemical weapons proliferated rapidly in the 1980s, in a process driven largely by their use in the Iran-Iraq war. A spate of biological weapons proliferation followed. But here too the trends are not straightforward. Implementation of the new Chemical Weapons Convention of 1997 is leading to a decrease in the number of states armed with such weapons (India and South Korea, for example, have signed the treaty and have promised to destroy their chemical weapons). In the biological area, there seems to be no increase in the number of states possessing or seeking such weapons since the number peaked at about a dozen in the early 1990s. If Iraq's biological warfare program is any indication, the proliferation of the 1990s may not be so much horizontal as vertical - other words, the problem is now one of an increasing number and quality of such weapons among already existing possessors, rather than an increase in the number of possessors.

Then there is the rest of the proliferation problem: ballistic missiles, cruise missiles, advanced conventional weaponry, small and light arms, new supplier nations, new risks of non-state actors gaining access to nuclear/biological/chemical weapons (NBC) or technologies. And there is even a new category of concerns over the proliferation of the science and technology base, and the dual-use technologies that go along with it.

To understand these increasingly complex phenomena, analysts continue to reach into the conceptual tool kit assembled by Wohlstetter and others in an earlier generation. But what drove nuclear proliferation in the 1950s and 1960s - major power competition - does not drive the proliferation trends of the 1990s, which result more from the asymmetric strategies of regional powers. Nor does the debate about the consequences of proliferation as framed by Wohlstetter, Kenneth Waltz...