the analysts concluded that Israel had not yet produced any weapons but that it would be hard for the international community to check such a decision if Israel believed that "the threat from the Arab states could no longer be contained by conventional means." According to Avner Cohen's major study, by May 1967, Israel had an operational nuclear weapon. Besides Israel, the analysts saw India as the only other "serious [contender] for nuclear status," with the latter "likely to undertake a nuclear weapons program in the next several years." In keeping with the 1965 INR contributions, Pakistan was on the list of potential nuclear states; so were the Australia, Canada, Switzerland, Taiwan, Indonesia, and the UAR [now Egypt]. The CIA partly declassified an interesting analysis of the "Snowball Effect" suggesting the larger impact of decisions on a nuclear capability by one or two countries. If India develops weapons, Pakistan will feel pressure to do so. The status of Chinese development also affects India. If Israel develops weapons, the UAR will feel pressure to do so One factor was whether a nation had domestic supplies of uranium. Countries with a domestic supply, and an appropriate level of technology, include India, Sweden, Australia and South Africa. Indian and Canadian reactors, at the time of the NIE, were the only ones that could easily produce weapons-grade plutonium. While Japan and West Germany have the technology base, their public opinion would be strongly against development. 1975 nuclear potential of nations Eight years later, the assessments had grown more complex. "The requisite materials and technology are already too widely available for technical safeguards and international regulation to be effective." While the author believed that there was "no hope of preventing nuclear proliferation," the study argued that it might be possible to influence the choices made by would-be nuclear states, e.g., to not go too far down the road to weaponization. Nuclear terrorism had come under discussion by the mid-1970s: "the same increasing availability of nuclear materials and technology which has made nuclear explosives accessible to developing states can also be expected sooner or later to bring them within the reach of terrorist groups."< This paper examines two kinds of proliferation: horizontal, or the spread of weapons to new actors, and vertical, or the development of additional capabilities (e.g., thermonuclear, miniaturized) for existing actors. There are two fundamental assumptions: Proliferation is first and foremost a political