In the mid-1990s, the primary threat posed by NBC weapons to the United States shifted from an all-out U.S.-Russian strategic exchange to less overwhelming, but more numerous and perhaps less predictable threats. The dissolution of the Soviet Union had turned some Russian weapons of mass destruction (WMD) strengths into weaknesses and the fear of "loose nukes"prompted the U.S. government to help shore up the safety and security of Russian WMD infrastructure. Around the same time, U.N. inspections uncovered Iraq's massive NBC weapons programs and a crisis erupted over the North Korean nuclear weapons program. It could no longer be assumed that the United States would face symmetric or parallel threats. A "paradox of the new strategic environment," according to then-Secretary of Defense William Cohen, was that "American [conventional] military superiority actually increases the threat of nuclear, biological and chemical attack against us by creating incentives for adversaries to challenge us asymmetrically." Accordingly, Congress has been concerned about the countries and groups that have nuclear, biological and chemical (NBC) weapons, are developing or trying to acquire them, and about those who have or seek missile delivery systems. The heightened sense of vulnerability to terrorism since the attacks in September 2001, coupled with reports of al Qaeda pursuing research on chemical, biological, radiological, and nuclear weapons, has focused attention on the connection between terrorism and WMD. In March 2002, President Bush stated that "... every nation in our coalition must take seriously the growing threat of terror on a catastrophic scale—terror armed with biological, chemical, or nuclear weapons." The unpredictability of terrorist efforts to acquire NBC weapons and a potentially higher probability of use pose a serious challenge to global stability and security. In particular, the Bush Administration has singled out state sponsors of terrorism with NBC weapons programs as particular security threats. U.S. and allied leaders and analysts continue to debate the exact nature and extent of the WMD threat. The status of nuclear, chemical, and biological weapons worldwide has changed only slowly over time. In absolute numbers, stockpiles are actually decreasing. Some U.S. and foreign analysts emphasize the positive impact of the demise of the Soviet Union and progress made in U.S.-Russian arms control and international arms control. Others emphasize the negative impact of the nuclear tests by India, Pakistan and North Korea; missile tests by North Korea, Iran, India, and Pakistan; continuing transfers of dangerous technology by states such as China, Russia, and North Korea; the activities of clandestine procurement networks; and a growing interest in NBC weapons among terrorists. This report focuses on the current threat and trends in nuclear, biological, and chemical weapons and missiles. Potential NBC weapons threats to U.S. security interests affect important national security and foreign policy decisions, including: the size and nature of the U.S. military force structure U.S. weapons and equipment acquisition U.S. doctrine and strategy for homeland defense and military operations abroad, including U.S. training for NBC environments foreign policy and economic policy toward countries of proliferation concern and their neighbors. In addition, the status and trends of these weapons are key factors in national and international debates regarding: the character of the threat to U.S. security posed by nuclear, chemical and biological weapons delivered by terrorists, missiles, aircraft, or ships whether states or groups are acquiring NBC weapons and missiles to deter or to attack regional powers or the United States whether intelligence estimates should be based on the capability and/or intent of countries and terrorist groups to use NBC weapons and missiles whether U.S. intelligence collection and analysis resources are adequate whether the United States should emphasize a strategy of deterrence, preemption, or national defense the appropriate mix of defense (active and passive), export control, assistance, and arms control the appropriate mix of unilateral, bilateral, and multilateral approaches. In the last decade, the U.S. government has taken many steps to address NBC weapons proliferation. For example, in December 2002, the White House released the "National Strategy to Combat Weapons of Mass Destruction," which divided relevant policy into three pillars: counterproliferation to combat WMD use; strengthened nonproliferation to combat WMD proliferation; and consequence management to respond to WMD use." Counterproliferation efforts include interdicting WMD materials, expertise and technology to hostile states and terrorist organizations, as well as deterrence, defense and mitigation. According to the 2002 strategy, these efforts also include preemptive actions to "detect and destroy an adversary's WMD assets before these weapons are used." Strengthened nonproliferation includes active diplomacy, multilateral regimes, threat reduction assistance, nuclear material and export controls, and nonproliferation sanctions. Finally, consequence management entails homeland defense against WMD threats. Several factors appear to facilitate the spread of dangerous technology to additional countries and groups. These same factors also might increase the likelihood that NBC weapons will be used (either militarily or for blackmail): Technological developments (in NBC, computer, and production technology). Increasingly free flow of information, people and goods. Growing disparities in conventional military capabilities. Growing disparities in strategic defenses. Continued prestige of nuclear power. Growing prestige of missile capabilities. Perceived utility of NBC threats to deter U.S. intervention. Perceived disdain by major powers for certain arms control agreements and international cooperation on nonproliferation. Threat assessments are highly debated exercises and necessarily subjective because they must assess not only technical capabilities (quantity and quality of weapons and control thereof) but also the intentions of the state or group that possesses the weapons (including options and thresholds for use). The connection between the existence of the technology or weapon and risk of use is not always clear. One school of thought is that the risk of use is directly proportional to the size of stockpiles or diffusion of technology or material. An opposing view is that the weapons themselves are manageable on a case-by-case basis. In general terms, the reduction of global and regional tension helps reduce the perceived need for weapons of mass destruction. Economic and political integration are also thought to reduce incentives for proliferation. The strong and credible U.S. deterrent capability might weaken the likelihood that some hostile countries will acquire or use WMD. Analysts debate whether U.S. development of a National Missile Defense system would deter the proliferation and use of WMD or would incite further proliferation. The NBC threat emanating from terrorist groups is even more complicated to assess. It is frequently argued that terrorist groups will find it easier to cross thresholds of NBC use than even some rogue states and that they will not adhere to traditional notions of deterrence. President Bush stated in a March 11, 2002, speech, "Some states that sponsor terror are seeking or already possess weapons of mass destruction; terrorist groups are hungry for these weapons, and would use them without a hint of conscience. And we know that these weapons, in the hands of terrorists, would unleash blackmail and genocide and chaos." The strong connection between the further spread of NBC capabilities to states and potential availability of technology to terrorists is not new. In the National Security Strategy for a New Century (2000), the Clinton Administration noted that the "proliferation of advanced weapons and technologies threatens to provide rogue states, terrorists and international crime organizations with the means to inflict terrible damage on the United States, our allies, and U.S. citizens and troops abroad." Two years later, the U.S. Special Representative for Nuclear Nonproliferation remarked to the NPT Preparatory Committee that "The spread of nuclear weapons to additional states not only increases the risk of nuclear war among nations, but also increases the risk of nuclear terrorism. The nuclear weapon program of a proliferating state, from the design of a weapon to its assembly, offers new opportunities for exploitation by terrorists. New stockpiles of weapons-grade nuclear material present a tempting target. Nations seeking nuclear weapons who also harbor terrorists represent a particularly severe threat to the civilized world." On the other hand, analysts debate whether rogue states themselves plan to use WMD against the United States. Some analysts doubt these countries would overtly attack the United States with WMD because of the U.S. ability to conduct an overwhelming counterattack. But others contend NBC weapons might nevertheless be seen by these countries as useful to limit U.S. military options and as a weapon of last resort, particularly where regime survival is at stake. The United States government works hard to decrease the risk of WMD use, the spread of such weapons and capabilities, and the U.S. vulnerability to the weapons. U.S. leadership has been critical for the NPT, the International Atomic Energy Agency (IAEA), the Nuclear Suppliers Group, Zangger Committee, a fissile material production moratorium, the Chemical Weapons Convention, Australia Group, Missile Technology Control Regime, Wassenaar Arrangement, START I, II, and III, and bilateral efforts with numerous countries to discourage the spread of weapons technology and the acquisition, deployment, or use of WMD. But various constituencies have criticized some recent U.S. actions for what they see as stimulating, as well as weakening the norms against, WMD proliferation: policies such as the development of a national missile defense; potential development of new nuclear weapons; withdrawing from the Anti-Ballistic Missile Treaty; discussions of regional missile defense systems in Asia and the Middle East; and refusal to consent to ratification of the Comprehensive Test Ban Treaty. Some critics are concerned that broader nonproliferation objectives will fall prey to shorter term goals in the war on terrorism. Abroad, observers have expressed concern that the United States is abandoning its arms control and nonproliferation leadership and that the U.S. emphasis on freedom of action will translate into other states seeking the same (e.g., Russia), to the detriment of the international nonproliferation regime.