Since the advent of the nuclear era in 1945, Americans and others have been debating whether or how it might be possible to prevent the proliferation of nuclear and other weapons of mass destruction (WMD). As each new proliferation challenge has emerged, debate about the shortcomings of the various policy tools for coping with proliferation has intensified. These debates have grown only more intense in the last ten to fifteen years. Despite such debates, American presidents have steered a fairly consistent course promoting nonproliferation, innovating along the way, while also coping with its periodic failures. The end of the Cold War seemed to make new things possible for nonproliferation, with the promise of even more cooperation between East and West on specific proliferation challenges. And the Persian Gulf War of 1990-91 seemed to make new things necessary, as the United States faced the first regional war under the shadow of weapons of mass destruction. First President George H.W. Bush and then President William Clinton committed the federal government to significant political efforts to strengthen the tools of nonproliferation policy.