School of Social and Economic Studies
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it focuses on the structural features that, in his view, have the greatest explanatory power, while bracketing the enormous diversity of state characteristics, domestic politics, and specific issues that distinguish individual states and relationships. Morton Kaplan, writing from a systems-theoretic perspective, defines the international system as a pattern of relations among states that can be characterised by a set of rules governing the behaviour of states within the system and a set of transformation rules describing how the system changes when its rules are violated or when its structure is disrupted. Kaplan identified six distinct types of international system — including the balance of power system, the loose bipolar system, the tight bipolar system, the universal system, the hierarchical system, and the unit veto system — each characterised by a distinctive pattern of behaviour rules and structural features. Kaplan's approach is more complex and typologically rich than Waltz's, but it has been criticised for being overly abstract and difficult to apply empirically. Hedley Bull, writing from the perspective of the English School, defines the international system as a society of states — what he calls the 'anarchical society' — governed by common rules and institutions that states have created to manage their relations with one another. For Bull, the international system is not merely a mechanical system driven by power politics: it is a social system in which states share certain common interests and values, recognise common rules, and participate in common institutions. This emphasis on the social and normative dimensions of the international system distinguishes Bull's approach from that of the structural realists and provides the foundation for the English S
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UNIVERSITY OF JUBA School of Social and Economic Studies Department of Political Science SIR 611 Essentials of International Relations MODULE 13 The International System Postgraduate Programme in International Relations Academic Year 2024–2025 Learning Objectives By the end of this module, students should be able to: Understand the concept of the international system and its significance in the study of international relations. Identify the main characteristics and structures of the international system, including anarchic order, sovereignty, and power distribution. Analyse how the international system shapes and constrains state behaviour across different historical periods. Examine the historical transformations of the international system from ancient times through the Westphalian era to the contemporary post-Cold War order. Evaluate contemporary developments and future trends in the international system, including the rise of emerging powers, globalisation, and new security challenges. MODULE OVERVIEW This module provides a comprehensive treatment of the international system — the foundational concept of international relations theory. Students will be introduced to classical and contemporary scholarly frameworks, examine the structural characteristics that define how states and other actors interact, and trace the evolution of the system from its Westphalian origins to the complex multipolar order of the twenty-first century. The module concludes by exploring future trajectories of the global political order and the implications for states, institutions, and global governance. 1.0 Introduction The international system is among the most foundational and contested concepts in the discipline of international relations. It refers, in its most general sense, to the pattern of interactions among states and other actors operating within an anarchic global political environment — an environment characterised by the absence of any supreme central authority above the level of the sovereign state. To understand international relations in any meaningful depth, one must first understand the structure, logic, and dynamics of the international system within which all international actors operate, compete, cooperate, and seek to advance their interests. The concept of a system implies something more than a simple collection of individual states. It implies that the units — primarily sovereign states, but increasingly also international organisations, non-state actors, and other entities — stand in structured relationships with one another, that these relationships follow identifiable patterns, and that the system as a whole has properties that cannot be reduced to the characteristics of any single unit acting alone. When scholars speak of the international system, they mean precisely this structured totality: the overall framework of political, economic, legal, military, and normative relationships that governs how states and other international actors relate to and interact with one another. The importance of the international system as a unit of analysis is one of the central contributions of structural realism, or neorealism, to the study of international relations. Scholars such as Kenneth Waltz argued that the structure of the international system — defined primarily by the distribution of power among the major states — is the most powerful explanatory variable in international politics. The anarchic structure of the system, in Waltz's view, generates certain recurring patterns of state behaviour — self-help, balance of power, security competition — regardless of the domestic characteristics of the states involved. This structural logic has been one of the most influential and debated ideas in international relations theory. Yet the international system is not a static entity. It has undergone profound transformations over the course of history, from the fragmented, locally bounded political orders of antiquity through the European state system established at Westphalia in 1648 to the truly global international system of the twenty-first century. Each of these historical phases of the international system has had its own distinctive structure, characteristics, and dynamics, and understanding the historical evolution of the system is essential to understanding its current form and anticipating its future development. 1.1 Meaning of the International System At its simplest, the international system can be defined as the totality of states and other significant actors interacting in the global arena, together with the structures, norms, and processes that govern those interactions. This definition captures three essential dimensions of the concept: the actors who constitute the system, the interactions that take place among them, and the structures and norms that shape and constrain those interactions. Each of these dimensions requires further elaboration. The actors within the international system are, first and foremost, sovereign states — the primary legal and political units of the system, endowed with territorial integrity, internal sovereignty, and formal equality under international law. However, the roster of significant actors in the contemporary international system extends well beyond states to include intergovernmental organisations such as the United Nations, the World Trade Organisation, and regional bodies such as the African Union; non-governmental organisations (NGOs) engaged in advocacy, humanitarian work, and norm promotion; multinational corporations whose economic activities span multiple jurisdictions; transnational civil society networks; and, increasingly, powerful individual actors whose platforms and resources give them significant influence on international affairs. The interactions that take place within the international system are extraordinarily diverse — encompassing diplomacy, trade, military competition, economic cooperation, cultural exchange, environmental negotiations, and countless other forms of inter-state and transnational activity. These interactions are not random: they follow patterns that reflect the interests, capabilities, and constraints of the actors involved, and that are shaped by the structural features of the system itself. Understanding these interaction patterns — their regularities, their drivers, and their consequences — is one of the central tasks of international relations theory. The structures and norms that shape interactions within the international system include both formal institutions — international law, treaty regimes, international organisations — and informal norms and expectations that, while not legally binding, nonetheless exercise a powerful influence on state behaviour. The norm of state sovereignty, for example, is one of the most fundamental structural elements of the international system: it establishes the basic rule that states are entitled to exercise supreme authority within their own territory and are not subject to interference in their internal affairs by other states. This norm has been repeatedly challenged and tested, but it remains a central pillar of the international system's architecture. 1.2 Importance of the International System in IR Studies The international system occupies a privileged position in the study of international relations because it provides the structural context within which all other phenomena of international politics must be understood. Just as social phenomena cannot be fully explained without reference to the social structures — institutions, norms, power relations — within which they occur, international phenomena cannot be fully explained without reference to the systemic context that shapes the interests, capabilities, and choices of states and other actors. A state's foreign policy, for example, cannot be understood purely in terms of its domestic politics and preferences: it must also be understood in terms of the systemic constraints and opportunities that the international environment presents. Different theoretical traditions in international relations have emphasised different aspects of the international system. Realists have focused primarily on the distribution of power within the system, arguing that this structural feature is the primary determinant of state behaviour and international outcomes. Liberals have emphasised the role of international institutions and interdependence in mitigating the competitive dynamics of the anarchic system. Constructivists have highlighted the constitutive role of norms, identities, and ideas in shaping how actors understand themselves and their interests within the system. Each of these theoretical perspectives captures important insights about different dimensions of the international system, and a full understanding of the system requires engagement with all of them. STUDY TIP When studying the international system, make sure to engage with the leading theoretical perspectives — realism, liberalism, and constructivism — as each illuminates different aspects of systemic dynamics. No single theory provides a complete picture, and the most sophisticated analysis draws on insights from multiple traditions. 1.3 Evolution of the International System The international system as we know it today is the product of a long historical evolution that has transformed both the actors and the structures of global politics. In ancient times, the political world was organised around regional orders — city-state systems, empires, and tribal confederacies — that had limited contact with one another and that lacked many of the features we associate with the modern international system. The concept of sovereignty, for example, was essentially unknown in the ancient world, where political authority was typically grounded in religious legitimacy, dynastic right, or military dominance rather than in the idea of territorially bounded legal supremacy. The decisive turning point in the evolution of the international system is conventionally located in the Peace of Westphalia of 1648, which ended the Thirty Years' War in Europe and established, for the first time in systematic form, the principle that Europe was composed of sovereign states possessing equal legal standing and the right to conduct their own internal and external affairs without interference. The Westphalian settlement laid the foundations of the modern state system, and the principles it embodied — sovereignty, territorial integrity, non-interference — continue to define the basic architecture of the international system to the present day, even as they have been increasingly challenged and qualified in the contemporary era. The subsequent evolution of the international system has been marked by several major transformations: the expansion of the European state system to encompass the entire globe through colonialism and later decolonisation; the emergence of international institutions and international law as increasingly significant elements of systemic structure; the experience of two world wars and the cold war, which dramatically reshaped the distribution of power and the institutional architecture of the system; and the contemporary transformations associated with globalisation, the rise of new powers, and the emergence of new transnational challenges. Each of these transformations has altered in important ways the structure, actors, and dynamics of the international system. 1.4 Components of the International System The international system can be analysed in terms of several key components that together constitute its overall structure and dynamics. The first and most fundamental component is the set of actors who participate in the system — states, international organisations, non-state actors, and others whose activities and interactions constitute the substance of international life. The second component is the distribution of capabilities among these actors — the relative power, resources, and influence that different actors command, which shapes the hierarchy and structure of the system. The third component is the set of interactions that take place among actors — the flows of goods, capital, information, people, and ideas that cross borders, and the diplomatic, military, economic, and cultural transactions that characterise inter-state and transnational relations. A fourth component is the normative and institutional framework of the system — the rules, norms, laws, and institutions that govern interactions among actors and that define the rights and obligations of states and other participants in the system. A fifth component, closely related to the normative framework, is the set of shared understandings and identities that shape how actors perceive their interests and understand their place in the system. These ideational components of the international system — emphasised by constructivist scholars — are not reducible to material power or institutional structure, but they play a crucial role in shaping how actors behave and how the system evolves. 1.5 Structure and Dynamics of Global Politics The structure of global politics at any given moment reflects the distribution of power among the major actors in the international system, the institutional and normative framework that governs their interactions, and the ideational context that shapes their perceptions and identities. These structural features are not fixed: they change over time as the distribution of power shifts, as new institutions are created or old ones weakened, and as norms and ideas evolve. Understanding the structure of global politics means understanding both its relatively stable features — such as the anarchic character of the system and the norm of state sovereignty — and its dynamic features — such as the ongoing shifts in the balance of power associated with the rise of China and other emerging powers. The dynamics of global politics — the processes by which the system evolves and changes — reflect the interaction of structure and agency. Structural forces — such as shifts in the distribution of power, the development of new technologies, and the emergence of new transnational challenges — shape the context within which actors make decisions and pursue their interests. But actors — states, international organisations, social movements, individual leaders — are not simply puppets of structural forces: they make choices, form coalitions, create institutions, and engage in ideational contestation that can in turn reshape the structural environment. The interplay between structure and agency is one of the central dynamics of the international system, and understanding it is essential to understanding how and why the system changes over time. 1.6 Overview of the Development of the International System The remainder of this module traces the development of the international system through its major historical phases and examines its principal structural characteristics, the actors who operate within it, and the dynamics of power that shape its evolution. Section 2 examines the conceptual meaning of the international system, exploring the major scholarly definitions and theoretical frameworks through which it has been analysed. Section 3 traces the historical development of the system from ancient times to the post-Cold War era. Sections 4 and 5 examine the structure and characteristics of the international system in detail. Section 6 surveys the major actors within the system. Section 7 analyses the role of power in shaping systemic dynamics. Sections 8 and 9 examine contemporary changes and challenges facing the system. Sections 10 and 11 look forward to the future of the international system and offer concluding reflections. KEY NOTE The international system is defined by three essential dimensions: the actors who constitute it (states, organisations, non-state actors); the interactions among them (diplomatic, economic, military, cultural); and the structures and norms that shape those interactions (anarchy, sovereignty, international law, institutions). All three dimensions must be understood to grasp the systemic logic of international politics. 2.0 Conceptual Meaning of the International System The concept of the international system is used in a variety of ways across the international relations literature, reflecting different theoretical perspectives and different levels of analytical abstraction. Some scholars use the term primarily to refer to the overall distribution of power among states — emphasising the structural constraints that this distribution imposes on state behaviour. Others use it to refer to the full range of relationships and interactions among all international actors — emphasising the complexity and diversity of global political life. Still others use it to refer to the normative and institutional order that governs international relations — emphasising the role of rules, norms, and shared expectations in constituting the system and enabling social interaction among its members. This section examines these different conceptual approaches and their implications for the study of international relations. 2.1 Definitions of the International System The variety of definitions of the international system in the scholarly literature reflects both the complexity of the phenomenon being described and the theoretical disagreements that have long characterised the discipline of international relations. Four definitions, each associated with a major scholar or theoretical tradition, illustrate the range of approaches that have been taken. Kenneth Waltz, the founding figure of neorealism, defines the international system primarily in terms of its structure — the distribution of capabilities among states. For Waltz, the defining characteristic of the international system is its anarchic ordering principle: unlike domestic political systems, which are organised hierarchically under a sovereign authority, the international system is characterised by the absence of any supreme authority above the level of the state. This anarchic structure, combined with the distribution of capabilities among states, generates the fundamental dynamics of international politics — self-help, the balance of power, and the security dilemma. Waltz's definition is deliberately spare and abstract: it focuses on the structural features that, in his view, have the greatest explanatory power, while bracketing the enormous diversity of state characteristics, domestic politics, and specific issues that distinguish individual states and relationships. Morton Kaplan, writing from a systems-theoretic perspective, defines the international system as a pattern of relations among states that can be characterised by a set of rules governing the behaviour of states within the system and a set of transformation rules describing how the system changes when its rules are violated or when its structure is disrupted. Kaplan identified six distinct types of international system — including the balance of power system, the loose bipolar system, the tight bipolar system, the universal system, the hierarchical system, and the unit veto system — each characterised by a distinctive pattern of behaviour rules and structural features. Kaplan's approach is more complex and typologically rich than Waltz's, but it has been criticised for being overly abstract and difficult to apply empirically. Hedley Bull, writing from the perspective of the English School, defines the international system as a society of states — what he calls the 'anarchical society' — governed by common rules and institutions that states have created to manage their relations with one another. For Bull, the international system is not merely a mechanical system driven by power politics: it is a social system in which states share certain common interests and values, recognise common rules, and participate in common institutions. This emphasis on the social and normative dimensions of the international system distinguishes Bull's approach from that of the structural realists and provides the foundation for the English School's distinctive understanding of international order. James Rosenau, writing from a transnationalist perspective, defines the international system as a network of global interactions that encompasses not only states but also a wide range of non-state actors — multinational corporations, international organisations, transnational social movements, and even individual citizens engaged in politically significant cross-border activities. Rosenau's 'turbulence model' of global politics emphasises the increasing complexity and fragmentation of the international system in the contemporary era, as the capacities and autonomy of non-state actors grow and as the ability of states to control cross-border flows declines. His approach anticipates many of the themes of contemporary globalisation theory and provides a useful counterpoint to the state-centric perspective of structural realists. Scholar Theoretical Tradition Definition of the International System Key Emphasis Kenneth Waltz Neorealism / Structural Realism A structure defined by the anarchic ordering principle and the distribution of capabilities among states Anarchic structure; power distribution; systemic constraints on state behaviour Morton Kaplan Systems Theory A pattern of relations among states governed by identifiable behavioural and transformation rules Typological variety; system rules; transformation dynamics Hedley Bull English School An anarchical society of states sharing common interests, rules, and institutions Social order; common norms; institutions; international society James Rosenau Transnationalism / Complexity Theory A network of global interactions encompassing states and a proliferating range of non-state actors Non-state actors; complexity; turbulence; globalisation Robert Keohane & Joseph Nye Liberal Institutionalism A complex interdependence structure in which multiple channels of interaction link states and societies Interdependence; institutions; multiple actors and issues Alexander Wendt Constructivism A social structure constituted by the shared knowledge, norms, and identities of the actors within it Social construction; ideational structures; identity and interests Table 1: Scholarly Definitions of the International System — Theoretical Traditions and Key Emphases 2.2 The International System as a Political Structure The characterisation of the international system as a political structure is central to the neorealist approach associated with Kenneth Waltz. A structure, in Waltz's framework, is defined by three elements: an ordering principle, the differentiation of units, and the distribution of capabilities. In the international system, the ordering principle is anarchy — the absence of a central authority above the level of the state. The units of the system — states — are formally undifferentiated, in the sense that they all perform the same basic functions (governance, defence, economic management, etc.) even though they differ enormously in their capabilities. The distribution of capabilities — the relative power of states — is the key variable that determines the specific structure of the system at any given moment, distinguishing between unipolar, bipolar, and multipolar configurations. The structural approach to the international system has the significant advantage of parsimony: it explains a great deal about international behaviour using a relatively small number of structural variables. The recurring patterns of international politics — the tendency of states to balance against dominant powers, the instability of hegemonic orders, the security dilemma that drives states into arms races and military competition — can all be explained, in structural realist terms, as consequences of the anarchic structure of the system and the distribution of capabilities within it, without recourse to detailed analysis of the domestic characteristics or specific preferences of individual states. However, the structural approach has also been criticised for its excessive parsimony — for abstracting away from the very features of international life that are most interesting and important. Critics argue that the structural realist framework cannot adequately explain variation in state behaviour among states facing similar structural constraints, the role of ideas and norms in shaping state interests and behaviour, the significance of international institutions and international law, or the politics of non-state actors and transnational civil society. These criticisms have driven the development of alternative theoretical approaches — including liberal institutionalism, constructivism, and critical theory — that seek to incorporate the factors that structural realism brackets. 2.3 Systemic Interaction among States The concept of systemic interaction captures the idea that the behaviour of states in the international system is not only determined by their own individual characteristics and preferences but is also shaped by their position within the system and their interactions with other states. Systemic interaction operates through a variety of mechanisms: strategic interaction, in which each state's decisions are affected by its expectations about how other states will respond; socialisation, in which states that participate in the international system come to adopt shared norms, identities, and practices through their interaction with other members; and diffusion, in which innovations — whether in military technology, economic organisation, political institutions, or normative standards — spread from one state to others through a variety of channels. The significance of systemic interaction is one of the key arguments for treating the international system as a distinct level of analysis — above the level of the individual state — in the study of international relations. The unit-level analysis, which focuses exclusively on the characteristics and choices of individual states, necessarily misses the systemic effects that emerge from the interactions of multiple states within a structured environment. The security dilemma, for example, is a systemic phenomenon: it arises not from the aggressive intentions of any individual state but from the logic of interaction in an anarchic environment, where any state's efforts to improve its security by acquiring more military capability will be perceived as threatening by other states, leading to counter-armament that leaves all states less secure than before. 2.4 International System and Global Order The concept of global order refers to the arrangements — formal and informal, institutional and normative, material and ideational — that provide a degree of stability, predictability, and regularity to international relations. Global order is not a synonym for peace or harmony: it simply means that international relations are conducted according to certain established patterns rather than in a condition of complete randomness or perpetual violent conflict. As Hedley Bull observed, order in international relations is consistent with a significant degree of conflict and competition among states: what distinguishes an ordered international system from a disorderly one is not the absence of conflict but the presence of shared rules and expectations that constrain how that conflict is conducted. The relationship between the international system and global order is complex and mutually constitutive. The international system provides the structural context within which global order is created, maintained, and transformed. But global order — through international institutions, international law, and shared norms — also shapes the international system by constraining state behaviour, facilitating cooperation, and providing mechanisms for the peaceful management of disputes. The post-1945 liberal international order, anchored by the United Nations system, the Bretton Woods institutions, and an extensive network of international law and norms, represents a particularly ambitious attempt to create a stable and cooperative global order within the framework of the anarchic international system. The current challenges to this order — from revisionist powers, populist nationalism, and the strains of globalisation — represent a significant test of its resilience and adaptability. 2.5 Anarchy in the International System Anarchy is the foundational structural condition of the international system — the absence of any supreme political authority above the level of the sovereign state with the power to make and enforce binding rules on all states. It is important to be clear about what the concept of international anarchy does and does not mean. It does not mean that international relations are characterised by constant chaos and violence — although it does mean that the threat of violence can never be entirely eliminated from inter-state relations. It does not mean that there are no rules or norms governing international behaviour — there are, and they are extensive and often effective. What it means, in essence, is that there is no international equivalent of a government — no supreme authority that can compel all states to obey international law, resolve disputes peacefully, or refrain from using force against one another. The implications of international anarchy for state behaviour are a central subject of debate in international relations theory. For structural realists, anarchy is the primary driver of international competition and conflict: in the absence of any guarantee of security from above, states must rely on their own capabilities and on self-help strategies to ensure their survival. This logic of self-help generates the recurring patterns of international competition, arms racing, and balance-of-power politics that realists see as defining features of international life. For liberal institutionalists, anarchy is a constant but not a constraint that cannot be overcome: international institutions can mitigate the competitive dynamics of the anarchic system by creating mechanisms for coordination, building trust, reducing transaction costs, and providing information that enables states to cooperate more effectively. DISCUSSION Consider the implications of international anarchy for the foreign policy choices of a small developing state like South Sudan. How does the anarchic structure of the international system shape the security dilemmas, alliance choices, and institutional participation of states with limited capabilities? In what ways does the presence of international institutions and norms modify the pure logic of anarchy? 2.6 The Role of Power Distribution The distribution of power among states is, for structural realists, the single most important variable in explaining the behaviour and outcomes of the international system. The concept of power in international relations is multidimensional: it encompasses military capability, economic resources, technological capacity, diplomatic influence, and the ability to shape the preferences and behaviour of other actors through attraction and persuasion. The distribution of these forms of power among states determines the hierarchy of the international system — identifying the great powers, the middle powers, and the small states that constitute the system's membership — and shapes the specific dynamics of competition and cooperation that characterise international politics at any given moment. Different distributions of power are associated with different structural configurations of the international system. A unipolar distribution — in which a single state possesses a preponderance of power that no