The most significant discourse about serious threats to U.S. national security in the twenty-first century will likely concern the military capabilities and intentions of nonstate actors, acting either for themselves, for religious elites, or as surrogates for state sponsors. This preoccupation results not from any inordinate fear of "terrorism" but from a recognition of objective military and political realities. While prior to 1991 only the Soviet Union possessed the capacity to inflict catastrophic military destruction on the United States, today that threat is vested in terrorist cells and religious sects that seek to destroy the fabric of the United States through unconventional military and paramilitary means. The terrorist attacks of 11 September 2001 bear this out. During the Cold War, the major threat to the United States was clearly the fear of miscalculation by the Soviets. Today, that threat has been recharacterized in terms of deliberate aggression against the United States by nontraditional actors willing to take suicidal risks to inflict premeditated, brutal savagery on innocent civilians in a manner designed to force not so much regime change directly as policy changes that affect regime change. Commitment to national security is only as valid as the policies and plans, military, economic, and political, that shape the areas and people from which these threats originate. The problem always has been to determine which policies, and how applied, make the greatest contribution to countering the threat--a threat now represented by social and religious systems that foster or at least condone aggressive response to differing religious and social values. This has never been more true than in Afghanistan and in Iraq. Security, then, means more than simply protecting the land on which we live; it embraces a comprehensive understanding of the appropriate response to human aspirations for improved conditions of life, for equality of opportunity, and for justice and freedom. Where these interests are thwarted for peoples or groups within a particular state or region by armed protagonists representing narrow, restrictive interests, our response must be one measured by the effective institutionalization of order. This monograph first examines the relationship between law and the use of force, to include a review of the principles of legal justification, the legal criteria for self-defense, and the policy of deterrence followed by the United States. It then examines the characteristic differences between the interpretive approaches taken by national and nonnational entities in their respective claims and counterclaims during international crises. Chapter 2, which concludes Part I, is focused on the historical aspects of the minimum world order system, which today comprises the prohibition against the use of force by one state against another embodied in Article 2, paragraph 4, of the United Nations Charter, with the exception inherent in customary international law and in Article 51 of the Charter that every state is authorized to use force in self-defense. A review of the pre-Charter system focuses on the development of the nation-state and the threads of international law development leading to multilateral agreements vice solely bilateral accords. The period following World War I, with the emergence of the League of Nations, is examined for its significance as an important source of the Charter of the United Nations. The structuring of the Charter is then addressed in terms of the concept of aggression and lawful response to aggression. Chapter 2 concludes with a review of the law of self-defense as defined first under customary international law and then under the UN Charter. Part II addresses lesser conflicts. Chapter 3 addresses instances where intervention is authorized in defense of humanitarian values defined in the UN Charter. The recent humanitarian interventions in the Congo and in Kosovo provide examples of authorized humanitarian initiatives. Chapter 4 examines the American intervention in Panama in 1989 as we intervened both to protect our interests under the Panama Canal Treaty and to ensure the safety of U.S. nationals present in Panama pursuant to that agreement. Chapter 5 reviews those conflicts in which terrorist violence by individuals, groups of individuals, and state-supported terrorist elements create a right to respond through military force by the target state. The attacks by Iranian militants in 1979 and by al-Qa'ida in 2001 spearhead the discussion of lawful response to terrorist violence. Chapter 5 argues that an effective counterterrorism strategy must ensure that enforcement measures are not legally constrained and that people responsible for terrorist acts are consistently held accountable by regional and international organizations. This expanding body of international law, when coupled with increasingly effective national legislation, appears to be arming the victims of terrorism with some of the legal instruments necessary to combat the threat. This chapter concludes that governmental response to state-supported terror violence, where the elements of necessity and proportionality are met, is clearly supported by customary international law and the UN Charter. Part III, consisting of chapters 6 and 7, addresses examples of major conflict. These are conflicts that have involved aggression by one or more nation-states against another nation-state, as opposed to the intervention by nations or coalitions of nations in response to either humanitarian crises or terrorist violence. In these major conflicts, the sovereignty of a nation is normally in dispute.While not necessarily exhibiting greater destructiveness than "lesser" conflicts, the more traditional international conflicts addressed in Part III invoke the law-of-war principles reflected in the Hague Conventions of 1899 and 1907 and the Geneva Conventions of 1949. Chapter 6 examines the coalition response to Iraqi aggression in 1990-91 during Operation DESERT STORM. It contrasts the illegality of the actions of the Iraqi regime of Saddam Hussein with the responses of the coalition led by the United States, which succeeded in liberating Kuwait and returning its borders to the status quo ante. The chapter begins with a discussion of Iraq's invasion of Kuwait and the response of the United Nations, leading up to the decision to use force. It then examines the conduct of armed hostilities by both sides during the war. The chapter concludes with observations on the role of law in the successes and failures of the postwar enforcement regime in Iraq. Chapter 7, Operation IRAQI FREEDOM, examines the Bush administration's decision to invade Iraq in March 2003 and enforce a long series of UN Security Council resolutions addressing Iraqi threats to international peace and security. This chapter examines these Iraqi violations in the context of international law principles justifying intervention.More significantly, it examines the right of states to enforce mandates issued by the Security Council and to redress violations of its edicts when the Council, as a body, refuses to do so. Part IV addresses U.S. policy for peace operations. The United States has voted to support the United Nations and NATO in providing multilateral forces to restore international peace and security. The United Nations was involved in both Chapter VI (peacekeeping) and Chapter VII (peace enforcement) operations in the 1990s, with limited success. Chapter 8, "Development of Criteria for Peace Operations," looks at the limitations inherent in UN leadership of such operations, citing the UN failures in Somalia and Bosnia. The success of NATO as the leadership element in Kosovo in 1998 was significant and may foreshadow a new era for the role of regional organizations (discussed in chapter 9) under Chapter VIII of the UN Charter. Part V concerns itself with special areas of legal concern that warrant consideration with regard to legal justification for military response to international coercion. This part, "Challenges for the Twenty-first Century," addresses the right of states to respond to threats to, and attacks on, critical infrastructure. Chapter 10 examines what rights, if any, in self-defense are triggered by attacks on infrastructure systems critical to our national political and economic integrity. Chapter 11, concerning computer network attack, takes this one step farther and examines the authority that international law provides to nations wishing to protect these systems aggressively, through preemptive defense. Chapter 11 carefully analyzes the right to target computer networks of nations that have expressed "clear indicators of attack." Finally, recommendations are offered to enhance the ability of the international legal system to support and embrace, strongly and legally, computer-generated data-warfare responses to such aggression. This Newport Paper examines representative instances where force has recently been used in international relations, the circumstances under which it was used, the instructive international policy and legal constructs that can be applied, and the relationship of these policies to the minimum world order system established in Articles 2(4) and 51 of the United Nations Charter. That system, defined more fully in the pages that follow, provides a complementary structure that prohibits and counters the unlawful, aggressive use of force, on the one hand, and permits national and collective self-defense, on the other, in a manner designed to meet both the traditional threats represented during the Cold War and the nontraditional threats we have seen recently and can expect in the future.