Irregular war, like war, remains an enduring feature of security studies both as they relate to internal state security and sovereignty as well as to international relations. Irregular war may not always appear to hold political purposes; many today seem driven by religious ideology, but the institution of theocratic governance has a politics of its own. Thus, like regular war, irregular war is subordinate to a political purpose. Whether they occur on the periphery of regular wars or perform roles to keep state competition from escalating into conflict, irregular wars are often intricately tied to their regular counterparts. While two broad theories of counterinsurgency both claim to have prescriptions for winning an irregular fight, one – the good governance approach – is plagued by problems of implementation at the governmental level, and the other – coercion – entails unreasonable brutality against both insurgent and population, often unbefitting a liberal counterinsurgent force.

While the academic study of International Relations immediately following the World Wars was focused on the causes of war and the conditions of peace, the diversification of IR in the mid twentieth century led to the creation of a discrete subfield of security studies. For the remainder of the twentieth century, this subfield focused exclusively on the problem of war – conventional and nuclear – between nation-states. But the end of the Cold War and the proliferation of multiple, opaque, and transnational security risks opened an intellectual space within security studies for a re-envisioning of the analytical approaches to security, as well as to a widening of the agenda. Security was no longer linked exclusively to war but also to a wider range of issues, and security was no longer exclusively conceptualized as the continued existence of the state but applied also to a multitude of actors.

This chapter looks at how energy fits into our understanding of international security as part of the widening of the security agenda. First, we define exactly what energy security means. Then we look at what theories of international security predict around energy security before moving on to a case study of the Middle East as an energy supplier. The chapter rounds out with a look at how the great powers in today’s international system are approaching the energy challenge.

Rational choice theory is a social theory of decision-making that assumes individuals, groups, organizations, and states are strategic actors and thus make rational choices based on their preferences, available information, and the expected outcomes of their actions. The theory is based on the Enlightenment idea that individuals are autonomous and should seek their own self-interest, and that we can determine how an individual should behave by understanding how they might best maximize the utility of their decisions. Game theory is an approach within the rational choice framework that models mathematically the mutual best responses of each player according to their preference orderings.

The concept of human security was first introduced formally in the 1994 UNDP Report and signaled a significant shift of focus from state security to the security of individual human beings and human communities. Unlike the abstract and theoretical debates within academia around that time about deepening and widening the definition of security, the human security approach was born from within the policy world and was policy-oriented. In the thirty years since its introduction, human security has undergone a series of reformulations, come under serious criticism, and inspired significant policy initiatives and numerous debates. Nevertheless, it remains the most formidable contender against traditional state-centered thinking around national and international security. In this chapter, we will look at the emergence and evolution of the human security approach, its core components, and its relationship with other important notions such as human development and responsibility to protect.

Peace Science research is interested in understanding the causal relationships between independent and dependent variables. Based on prior knowledge or existing theories, they develop hypotheses about the strength and direction of impact of independent variables on dependent variables, whether they be arms races and war, economic stability and civil war, or democracy and peace. Quantitative methods provide researchers with a way of confirming or disconfirming these hypotheses.

Critical Security Studies (CSS) is a diverse and multidisciplinary field that approaches traditional security studies through a critical lens and examines the ways in which security discourses and practices reify and reinforce existing power relations and contribute to the marginalization, oppression, and precarity of various groups of people. CSS scholars ask whose security we center when we talk “Security,” and whose security we neglect or sacrifice, what issues are present/absent, who is afforded agency, and who appear only as voiceless victims. They examine the ways in which security and power are intertwined so that evoking security can generate power, enable various kinds of interventions, perpetuate relations of domination and subjugation, and reproduce social hierarchies. Many CSS scholars adopt an interpretivist methodology and normative approach to scientific knowledge; they are interested in analysis not just for the sake of it but for bringing about change to the status quo.

To link the economic sphere of international relations to the security sphere of international politics in this chapter, we treat economics as a function of politics and security. While controversial in some circles, this need not be so. Economists, historians, and political scientists have distinct answers to questions concerning the economy. That they differ in scope, interest, and focus should be viewed as alternatives for assessing the empirical world, not mutually exclusive representations of it. This is fundamental to the interdisciplinary approach of International Security. It should be no surprise that the vastness and complexity of the global economic system intersect with realms outside the purview of economics. Security is an arena in which the politics of economic decision-making are felt most intensely.

“Alignment” is an umbrella term to describe a relationship between two or more states that involves mutual expectations of some degree of policy coordination on security issues under certain conditions in the future. The types of alignment explored in this chapter are alliances, thin and thick security institutions, coalitions, and strategic partnerships. The distinguishing features of these alignments are their differing levels of formality and the reason for their creation, or their objectives. Strategic alignments remain one of the dominant means that sovereign states possess to cooperate and coordinate their actions around common threats and political interests. States are either pulled into distrustful relations through security dilemmas or they are obliged to work together to solve common problems. Alliances, security institutions, coalitions, and strategic partnerships offer a variety of ways that states may seek to address security issues, threats, or challenges to their territories or interests.

Global public health is now seen as a security issue by many nations across the globe. Aside from naturally occurring outbreaks of infectious disease, deliberate attacks involving biological agents have emerged as a major security concern and a source of public anxiety in recent decades. Though many public health and security experts now recognize that effective prevention and response to these threats depend on building resilient public health systems around the world and international cooperation in maintaining them, it is unclear that the kind of sustained political will and economic resources exist to address such a massive undertaking that would need to take a holistic approach to human security and incorporate measures addressing: poverty; food insecurity; environmental degradation; lack of access to basic health-care services; adequate education; housing; sanitation and clean water; as well as more conventional aspects of security.

This chapter dissects the challenges posed by weapons of mass destruction. It starts by exploring the weapon that changed the fundamentals of security and warfare – the atomic bomb with a brief look at how nuclear weapons work. Then it examines three cases focused on nuclear weapons: nuclear weapons in the Cold War, nuclear-weapon states in the twenty-first century, and non-state actors and the nuclear dilemma. The chapter rounds out with a look at the role chemical and biological weapons play in the contemporary world, offering some concluding thoughts on weapons of mass destruction and contemporary international security.

Environmental security broadly refers to the relationships between the environment and national, human, and ecological security. This encompasses how environmental changes affect or interact with violence, armed conflict, state stability, livelihoods, food security, economic stability, general human well-being, and more. This chapter unpacks environmental security by focusing on how environmental change and disaster impact humans, states, and the international order, respectively. Although many security studies scholars still question whether the environment should be considered a security issue or just a pressing policy issue, this chapter demonstrates the serious security issues that arise with the onset of environmental change. Regardless of the outcome of these academic debates, these challenges are very real for policy makers, who are working to anticipate and manage the challenges that the environment will pose to international security.