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International Relations Theory

A Primer for Practitioners

Joel Hillison, PhD; Zenel Garcia, PhD; and M. L. deRaismes Combes, PhD

27 July 2026

https://doi.org/10.36304/ExpwMCUP.2026.09

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Abstract: This article provides a practical primer on major international relations (IR) theories, realism, liberalism, and constructivism, and illustrates how each offers distinct explanations for cooperation, competition, and conflict. It highlights how these theories function as analytical heuristics for strategic leaders, clarifying causal mechanisms that shape global outcomes. The article applies these perspectives to post–Cold War U.S.–Russia relations, showing how understandings of anarchy, power, and security influenced periods of engagement and confrontation. Emphasizing that no single theory captures the complexity of world politics, the authors argue that theoretical fluency enables practitioners to make more balanced judgments and develop effective policy formulation.

Keywords: international relations, IR, realism, liberalism, constructivism, Russia, Ukraine

 

Strategic leaders often turn to international relations (IR) theories to make sense of how the world works. These theories serve as heuristics, offering structured ways to think about global dynamics and making recommendations or decisions quickly and effectively. Yet, leaders are more likely to make sound judgments when they can draw from a diverse toolkit of theories rather than relying on a single perspective. Such theoretical fluency helps prevent biases and blind spots that may arise from viewing every situation through one narrow lens—a risk that can have serious consequences. IR theories provide analytical frameworks for interpreting the global environment and anticipating how actors may respond to events or policies. While the field encompasses a wide range of approaches, most theories fall within three main traditions: realism, liberalism, and constructivism.

Each of these theories explains the world by emphasizing how the application of different elements of the global system—what scholars often refer to as causal mechanisms—result in specific outcomes given certain conditions. Still, the complexity of the global environment means that these theories necessarily simplify how states engage with and react to various, often opposing forces. As international relations scholar Robert Jervis argued, “Only rarely does a single factor determine the way politics will work out.”[1] Rather, a fluid understanding of these theories and how they contrast and complement one another can help guide practitioners in making national policy decisions and formulating strategies to best promote national interests. This article serves as a primer for those theories, focusing on their basic assumptions about how the world works and what they say about the conditions required for cooperation, competition, and conflict. It begins with a summary of the three broad theoretical schools before launching into how they view international relations. Each school of thought has a different understanding of the organization of the international system. They focus on different actors, interests, and aspects of power. Finally, each school provides a unique frame, or lens through which to interpret what happens in the world, in this case, U.S.–Russian relations.

 

Realism(s)

Realism is arguably one of the oldest schools of IR and addresses the question: Why war? It finds much of its explanatory power in human nature and the power dynamics of the international system. Classical realists, such as Hans Morgenthau, locate the root cause of conflict in human nature, specifically an innate drive for power that statesmen carry into the conduct of foreign policy. Structural realism, or neorealism, as developed by Kenneth N. Waltz shifts the explanatory focus from human nature to the architecture of the international system, arguing that competitive state behavior is a product of systemic pressures rather than individual disposition. Despite this difference in causal emphasis, both variants agree on three characteristics that explain state behavior: the ordering principle of the system, the relevant actors, and the distribution of power among them.[2]  

Whereas most states have a hierarchical system with a sovereign power who makes and enforces rules, realists emphasize that the international system is characterized by anarchy, meaning that there is no overarching system-level authority to govern interactions among states. Realists liken this condition to Thomas Hobbes’ state of nature, where there is no agreed-on actor to enforce rules, and where life can be “solitary, poor, nasty, brutish, and short.”[3] Structural realists arrive at the same conclusion through a different pathway: it is not human nature but the absence of a central authority that forces states into self-help behavior. Either way, the result is a self-help system where trust is low and any other state can represent a threat.

Realists contend that states are the main actors in this system and that only great powers are truly worthy of scrutiny. While realists acknowledge other actors in the international system, such as international organizations, they believe that these other actors merely reflect either the balance of power, as was the case in the formation of the United Nations or, more commonly, the interests of powerful states that will limit the influence of these organization in areas of “high politics” such as national security, foreign policy, and core questions of sovereignty.[4]  

Both classical and structural realists agree that state behavior is driven by the logic of consequences—states weigh costs and benefits before acting and select the path that best advances their objectives. Where they differ is in the source of those objectives. For Morgenthau, interests are ultimately an expression of the drive to seek power embedded in human nature; the statesman’s task is to channel that drive rationally in pursuit of the national interest. For structural realists, interests are shaped by position in the system: states pursue what the anarchic structure compels them to pursue, regardless of the preferences of individual leaders. In both accounts, however, survival is the most basic interest of all states.  

Within structural realism, two variants have emerged that differ on the behavioral implications of anarchy. Offensive realists argue that since “states can never be certain about the intentions of other states,” they must pursue power maximization and seek dominant status, or hegemony, over other states to ensure their survival.[5] In contrast, defensive realists argue that states pursue security maximization rather than dominance, therefore, states are more prone to balance against threats than seeking dominance.[6] The tragedy, recognized across all realist variants, is that as states seek to become more powerful or more secure, they often end up less secure. Even defensive actions can be interpreted as threatening to other states, leading those other states to bolster their own defenses, and so on, in what is known as the security dilemma.[7] The result is a far greater likelihood for conflict, even if neither side wanted it. Conflict is also more likely when a rising power challenges a declining hegemon.[8]  

While offensive and defensive realism differ in how they view the behavioral implications of anarchy, they both agree that material power is the main variable in international relations, understood primarily through a military lens. Economic capacity matters to realists largely insofar as it can be converted into military power, which is then used to coerce other states. Given the realist view that virtually all states retain the potential for military capacity, even those without standing armies, and that state intentions can never be truly known, interactions among powerful states are often viewed through a zero-sum lens. If one state gains, another state necessarily loses. When states do cooperate, that cooperation is often short lived and limited in scope. Jack Snyder wrote, “at realism’s core is the belief that international affairs is a struggle for power among self-interested states.”[9] 

 

Liberalism(s)

The liberal school of thought pushes back against this realist focus on the likelihood of interstate conflict by arguing that certain mechanisms influence states to cooperate often. In essence, they are addressing a different question of why not war? Three prominent strands of liberalism stand out: democratic peace theory (sometimes called liberal internationalism), liberal intergovernmentalism, and neoliberal institutionalism. Democratic peace theory—rooted in the Enlightenment ideas of Immanuel Kant and developed by scholars such as Michael W. Doyle and Bruce Russett—takes a normative approach that focuses on a state’s internal governance. It holds that democracies tend to act differently toward one another than toward nondemocracies, engaging in peaceful relations based on shared norms, mutual accountability, and institutional checks.[10] The corollary is that as the number of democracies in the international system increases, the likelihood of sustained peace rises.[11]

Liberal intergovernmentalism, developed by Andrew Moravcsik, offers a three-stage account of how states behave in international politics.[12] During the first stage, national preferences are formed domestically through the competition and aggregation of societal interests—those of individuals, firms, and organized groups—which the state then represents in international negotiations. For the second stage, states bargain intergovernmentally on the basis of those preferences, with outcomes shaped by the asymmetric interdependence among them: states that have more to gain from an agreement, or more to lose from its failure, bargain from a position of relative weakness. During the third stage, states design international institutions to lend credibility and durability to the commitments they have reached, delegating authority only where it serves to resolve specific commitment problems or reduce transaction costs. What distinguishes liberal intergovernmentalism from realism and constructivism is that while realists derive state interests from systemic position, and constructivists derive them from socially constructed identities, liberals treat preferences as prior and politically determined at home. The practical implication for strategic leaders is consequential: understanding why a state pursues a particular foreign policy requires looking inside the state at its domestic political economy, not only at the distribution of power in the system or the cultural context of its interactions.

Neoliberal institutionalism, as theorized by Robert O. Keohane, Joseph S. Nye, and others, shifts the focus from domestic structure to the external operating environment. It argues that complex interdependence—built through trade, treaties, and international organizations—creates patterns of interaction that raise the costs of conflict, reduce uncertainty, and foster cooperation even among states with dissimilar regimes.[13] While all three strands share realism’s starting assumption that the international system is anarchic and trust is difficult, they contend that democracy, domestic preferences, and institutionalized interdependence can mitigate anarchy’s harsher effects, including the security dilemma.

Like realism, these liberal theories generally view states as the primary actors, but neoliberal institutionalism also gives significant analytical weight to the institutions and organizations through which states interact. Nonetheless, although other schools of thought—notably constructivism—see some of these bodies as having agency in their own right, neoliberalism sees such institutions as forums for states to pursue and coordinate their interests.[14] Crucially, liberalism broadens the definition of those interests beyond mere survival to include economic prosperity, stability, and peaceful coexistence.[15] Power is therefore measured not only in military might but also in wealth and stability, and cooperation is evaluated in terms of absolute gains—the idea that all states can benefit from shared growth—rather than purely relative gains.[16] While realism questions whether institutions can truly override power politics or whether democracies are always peaceful, liberal theories remain central to understanding why cooperation persists in a competitive world.  

 

Constructivism

Constructivism represents a significant “turn” in IR theory, challenging dominant realist and liberal approaches by asking how we might envision the global system, and war, differently. It focuses on the social construction of world politics, asking how concepts like anarchy come to mean what they do, and how those meanings can change. For practitioners, this means understanding that the international system is not just a given set of rules, it is constantly being constituted and reconstituted by how countries interact and what they understand those interactions to mean. Unlike the realist and liberal paradigms that see anarchy as a naturally given condition of the international system that produces fixed behaviors like self-help, competition, or cooperation, constructivism argues that anarchy itself is not inherently competitive or cooperative.[17] Instead, it is like an “empty vessel” that takes on meaning based on the shared understandings and practices of states.[18] Thus, constructivists might address the question, what is the meaning of war?

In other words, how states behave in an anarchic world, whether they are enemies, rivals, or friends, is determined by their interactions over time and the common ideas they develop about each other. Alexander Wendt, a key constructivist, explains that states act differently toward friends than enemies because of these shared meanings. The idea of “self-help,” where states can only rely on themselves for survival, is not a natural outcome of anarchy but an institution that has been socially constructed through historical interactions.[19] This means that if states change their practices and perceptions, the nature of anarchy can change from conflictual to cooperative.[20]  

Constructivism also fundamentally changes how we think about power. It is not just about material power, such as military might or economic strength. Instead, power also has a social and ideational dimension. In this view, power is not just used to make others do something (coercive power); it also shapes who actors are and what their interests are (constitutive power).[21]

For example, nuclear weapons are seen differently depending on the context: the United States is not worried about the nuclear weapons held by the British but would be very concerned if North Korea acquired even a few.[22] This shows that material capabilities get their meaning from the social context and shared understandings.[23] The ability to define what is normal, legitimate, or threatening is a crucial aspect of power. This implies that to understand power dynamics, practitioners must look beyond military budgets and consider the “distribution of knowledge” and collective meanings that influence how capabilities are perceived and used.[24]  

This understanding of anarchy and power results in a different framing of security. From a constructivist standpoint, security is not just about protecting a state’s physical borders or surviving threats. Instead, threats are socially constructed, meaning they are defined by how states interpret themselves and others.[25] What one state considers a threat, another might not, even if facing similar material capabilities.  

State identities and the relationships between states are central to defining security interests. For instance, the “security dilemma,” where one state’s efforts to increase its security can unintentionally make others feel less secure, is viewed not as an inevitable outcome of anarchy, but as a product of sustained interactions and how states come to see each other.[26]  

Constructivists highlight how shared norms and collective identities can mitigate or even overcome such dilemmas. The absence of war between liberal democracies, for example, is often attributed to shared norms of compromise and cooperation that prevent conflicts from escalating. This suggests that building trust and shared identities can fundamentally alter security perceptions, making cooperation more likely.[27] Even basic concepts like national territory and sovereignty, which seem natural, are in fact socially recognized understandings that shape how states define their security.[28]  

In essence, constructivism provides practitioners with a framework to understand that international relations are profoundly social, driven by ideas, norms, and identities that are continuously built and redefined through interaction. This means that changes in beliefs and shared understandings can lead to fundamental shifts in how anarchy, power, and security are experienced and managed in world politics. 

 

Post–Cold War U.S.–Russia Relations

Applying these theoretical lenses to U.S.–Russia relations across different historical moments demonstrates both their utility and their limits. The immediate post–Cold War decade from 1989 to 1999 provides a case where hopes for liberal integration clashed with persistent realist concerns about power balances and North Atlantic Treaty Organization (NATO) expansion, while constructivist perspectives help explain shifting identities as Russia sought to redefine its role in the international order. In contrast, the period from 2014 to 2022—defined by the annexation of Crimea, escalating sanctions, and the war in Ukraine—shows a resurgence of realist competition alongside liberal efforts to reinforce international institutions and norms. Comparing these two eras illustrates how realism, liberalism, and constructivism each highlight different aspects of U.S.–Russia relations, and why strategic leaders benefit from drawing on multiple theories to understand evolving challenges. Table 1 summarizes the core assumptions, key theories, and predicted state behaviors of these three theoretical traditions, providing a comparative reference point for the case studies that follow.

 

Table 1. IR theoretical paradigms across core concepts

Core concept	Realism	Liberalism	Constructivism
Central question	Why war?	Why not war?	What is the meaning of war?
Ordering principle	Anarchy: no authority governs state interactions; a self-help system where any state may be a threat	Anarchy acknowledged, but its effects are mitigated by democratic norms and institutions	Anarchy is an “empty vessel”; its meaning is socially constructed, not structurally fixed
Main actors	States, especially great powers; other actors merely reflect underlying power balances	States are primary, but institutions and domestic politics independently shape outcomes	States whose identities and interests are constituted through interaction; norms and ideas also matter
Nature of power	Material and primarily military; economic capacity matters only insofar as it converts into military power	Broadened to include economic and institutional influence; measured in absolute, not only relative, terms	Material and ideational; power also constitutes actor identities and interests, not only capabilities
Source of state interests	Classical realists: human nature and the will to power. Structural realists: position within the system. Both treat survival as the primary interest	Domestic politics and regime type; interests extend beyond survival to prosperity and peaceful coexistence	Interests are not a given, they are socially constructed through interaction, identity, and shared norms
View of cooperation	Possible but rare and short-lived; always vulnerable to relative-gains concerns and shifting power balances	Sustained cooperation is achievable; interdependence and institutions raise the costs of conflict	Cooperation emerges when states develop shared identities and norms; not blocked by anarchy per se
View of institutions	Institutions reflect the balance of power and offer only a “false promise” of security; great-power interests prevail	Institutions reduce uncertainty, lower transaction costs, and sustain cooperation independently of hegemonic power	Institutions embody shared norms and can reshape state identities, redefining what interests states pursue
Security dilemma	Structural and largely unavoidable; even defensive build-ups are perceived as threatening, generating conflict spirals	Mitigated among democracies through shared norms and institutional transparency	Not inevitable; a product of adversarial identities that sustained hostile interaction creates, and can transform

Source: compiled by the authors.

 

 

Realism and Liberalism in U.S.–Russian Relations in the 1990s 

The period following the fall of the Soviet Union was marked by widespread euphoria and optimism about a new international order. By 1989–90, perceptions of the U.S.–Soviet relationship had begun to shift dramatically. During a series of negotiations among President George H. W. Bush, Chancellor Helmut Kohl, and President Mikhail Gorbachev, Moscow accepted the reunification of Germany within the framework of the NATO alliance—a development that would have been unthinkable just a few years earlier.[29] Traditional realist and liberal frameworks struggled to account for this dramatic redefinition of Soviet interests. Constructivist scholars, however, pointed to processes of “truth-seeking discourse” and debates over norms such as national self-determination to explain the transformation in Soviet thinking.[30]

After Russia emerged as an independent state in 1991, perceptions of the international system shifted as both Washington and Moscow advanced new narratives about their relationship and the potential for cooperation within existing and revised institutional frameworks. Realists, however, viewed this with skepticism, warning that the expansion of institutions such as NATO and the European Union carried inherent risks and would eventually provoke resistance from Moscow.[31] Liberals, by contrast, celebrated the Soviet collapse as a triumph of democratic and market values, encouraging reforms in Russia and across the former Soviet and Warsaw Pact states.[32] Liberal institutionalists sought to embed Russia more firmly within the Euro-Atlantic community through initiatives such as NATO’s Partnership for Peace, the establishment of the NATO–Russia Council, and Russia’s admission to the G7. Meanwhile, constructivists argued that the post–Cold War order was not predetermined by great-power rivalry; rather, they argued that anarchy was “what states made of it,” and that new identities and shared norms could reshape international politics.[33]

This period witnessed the growing influence of regimes and international organizations, as neoliberal institutionalist emphasized the ability of institutions to foster cooperation and increase the costs of conflict. Neoliberal institutionalists argued that these entities, offered tangible functional benefits: NATO, for example, not only provided information and monitored compliance with agreements, but also created focal points for collaboration and reduced the transaction costs of repeated interactions through its integrated military structure.[34] Neoliberal internationalists also championed the expansion of both NATO and the European Union to enhance security, promote prosperity, and advance the spread of democratic values and individual freedoms. Realists countered that NATO had lost its strategic rationale with the collapse of the Soviet Union and should have been dissolved rather than preserved. From a structural realist standpoint, the specific mechanism at work was straightforward: expanding a military alliance into the security buffer of a great power triggers balancing behavior, because the distribution of capabilities—not stated intentions—determines threat perception. By this logic, Russia’s eventual resistance was not a failure of diplomacy but a predictable systemic outcome.

At the same time, perceptions of power were shifting as the United States, its NATO allies, and Russia all reduced military spending and force structures in pursuit of a so-called “peace dividend.” Commentators captured the spirit of the era in different ways. Charles Krauthammer famously declared a “unipolar moment” in his 1990 Foreign Affairs article, highlighting U.S. primacy, while Francis Fukuyama’s The End of History and the Last Man framed the period as the triumph of liberal democracy and free markets.[35] The post–Cold War environment suggested that states were prioritizing goals beyond security—such as economic integration, prosperity, and the promotion of democratic values—over traditional great-power rivalry.

By 1994, however, early signs of diverging interests between Washington and Moscow were already evident. U.S. support for NATO enlargement provoked strong objections from Russia, a concern that President Boris Yeltsin communicated directly to President William J. “Bill” Clinton.[36] Realists were unsurprised by Russia’s reaction, interpreting it as a predictable zero-sum response to the expansion of a military alliance on its borders. Yet, cooperation nonetheless persisted. Russia participated in NATO stabilization efforts in Bosnia-Herzegovina in 1995–96, signed the NATO–Russia Founding Act in 1997, and engaged in the newly established NATO–Russia Council in 2002.[37] Liberal theorists could also point to collaboration on nuclear nonproliferation, most notably the 1994 agreement in which Russia, the United States, and the United Kingdom persuaded Ukraine to relinquish its Soviet-era nuclear arsenal in exchange for security assurances.

The turning point came in March 1999 with NATO’s initiation of Operation Allied Force against Serbia and its bombing campaign in Kosovo. Realists were not surprised that NATO pressed forward despite Russian opposition, calculating that Moscow—economically fragile and militarily weakened in the aftermath of the 1998 ruble crash and widespread corruption—had limited capacity to respond. Still, Russian frustration manifested symbolically in the surprise occupation of the Pristina airport in June by Russian forces ahead of NATO’s arrival. Although tensions eventually subsided and Russia joined the NATO stabilization force under U.S. command, the post–Cold War honeymoon was effectively over. The transition from Yeltsin to Vladimir Putin in 2000 further reshaped the trajectory of U.S.–Russia relations, which between 2000 and 2014 oscillated between moments of cooperation, including attempts at “resets,” and intensifying competition across various regions.

 

Constructivism and U.S.–Russia Relations in the 1990s 

A constructivist perspective reveals U.S.–Russia relations in the 1990s as shaped by a complex interplay of socially constructed identities, interests, and the meanings attached to anarchy, power, and security, rather than being driven solely by material capabilities or a fixed anarchic structure. For constructivists, the competition between the United States and Russia was not a fixed material condition but an “empty vessel” shaped by states’ intersubjective understandings and practices. Accordingly, the end of the Cold War left both the United States and the newly independent Russia in a state of uncertainty regarding their relationship and interests, marking a shift from a “competitive security system” to a period conducive to identity formation.[38]

From this perspective, power is not merely material capabilities but derives its meaning from the social context through which it is interpreted. The end of the Cold War, which dominant rationalist theories failed to predict or adequately explain, highlighted this very point: the “givens” of international politics were suddenly contingent and open to change.[39] The profound shift in Soviet foreign policy under Gorbachev, the so-called “New Thinking,” exemplified an intentional transformation, moving away from the Leninist theory of inherent conflict with capitalist states. This was facilitated by the collapse of Soviet economic power, a material factor that empowered new thinkers who then promoted ideas of “common security” imported from Western liberal internationalists.[40] Gorbachev’s strategy involved unilateral initiatives and self-binding commitments to build trust and altercast (project an identity) the West into a cooperative role, thereby attempting to reshape the intersubjective structures that defined their competitive identities.[41] 

Consequently, the security relationship between the United States and Russia in the 1990s was not predetermined by material power balances but was instead a dynamic process of identity formation, where the content of their security interests, and even their national identities, was continually being negotiated and constituted through their interactions. The extent to which a cooperative or competitive security system emerged depended on the practices and reciprocal recognition of new identities and interests. Thus, a constructivist approach emphasizes that the outcomes of U.S.–Russia relations were contingent on what both states collectively made of their anarchic environment by continuously producing and reproducing their identities and interests through their practices. 

 

The Turning Point in U.S.–Russia Relations  

The period from 2000 to 2014 marked a decisive shift in U.S.–Russia relations. Realists argued that U.S. policy, shaped by liberal assumptions, ignored enduring power politics and made renewed tensions inevitable. After the 11 September 2001 attacks, the U.S. intervention in Afghanistan drew broad support, but the 2003 invasion of Iraq provoked international condemnation, with France and Germany engaging in “soft balancing” alongside Russia’s objections. NATO enlargement further strained relations, especially the 2008 pledge to admit Georgia and Ukraine. The U.S. withdrawal from the Anti-Ballistic Missile Treaty in 2002 and plans to deploy missile defenses in the Czech Republic and Poland drew sharp criticism from Moscow, despite Washington’s assurances that the systems were defensive.[42] NATO’s 2011 military campaign in Libya added to Russia’s growing list of grievances.[43]

Liberals and constructivists highlighted different dynamics. Liberals pointed to institutional failures, noting that opportunities to embed Russia more deeply into cooperative frameworks were squandered as NATO and the EU pressed eastward.[44] Constructivists emphasized the clash of narratives: for the West, enlargement symbolized the spread of democracy and stability, while for Russia it reinforced a sense of exclusion and encirclement. These competing interpretations came to a head over Ukraine.[45] The EU’s pursuit of an association agreement—countered by Moscow’s push for Ukraine to join the Eurasian Customs Union—intensified tensions. Following the Maidan protests and the flight of Ukrainian President Viktor Yanukovych to Russia, Moscow annexed Crimea and supported separatists in the Donbas.[46] For defensive realists in particular, this outcome confirmed the logic of the security dilemma: Georgia and Ukraine’s efforts to improve their security by aligning with NATO and the EU were interpreted by Moscow as threatening, provoking intervention that ultimately left both states less secure than before—a textbook illustration of how security-seeking behavior can generate the very insecurity it was meant to prevent.

 

Realism and Russia’s Invasion of Ukraine, 2014–Present 

From a realist perspective, Russia’s actions in Ukraine from 2014 to 2022 were a reversion to the normal behavior of great powers and further evidence of the “false promise” of international institutions. Offensive realists would interpret Russia’s annexation of Crimea and support for Donbas separatists as classic power-maximizing behavior: Moscow seized the opportunity created by Ukraine’s political instability to expand its sphere of control and push back against what it perceived as encroaching Western hegemony.[47] Defensive realists, by contrast, might frame the same actions through the security dilemma; Russia’s moves were driven not by an inherent drive for dominance but by a perceived need to buffer itself against NATO expansion, a reactive escalation that in turn accelerated precisely the Western alignment Moscow sought to prevent. This view is consistent with how Russian leaders describe the conflict.[48] Both variants might agree, however, that the outcome vindicated structural realism’s core claim: institutions could not override the logic of great-power competition when core security interests were at stake. As Russia and China expanded their military capabilities while the United States remained entangled in protracted conflicts such as Afghanistan, both powers sought to balance against U.S. influence. For realists, this dynamic signals the erosion of unipolarity and the reemergence of a multipolar international system defined by renewed great-power rivalry.

What realists had long argued—that institutions cannot override power politics—appeared increasingly validated as great powers acted unilaterally. Nowhere was this more evident than in the erosion of the nuclear nonproliferation regime. Ukraine’s decision to relinquish its Soviet-era nuclear arsenal and join the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) in 1994 was premised on security assurances from the United States and Russia. Moscow’s invasions of Ukraine in 2014 and 2022 starkly revealed the fragility of those guarantees and, for realists, the folly of relying on institutions over power.[49] The broader arms control framework also deteriorated: the United States withdrew from the Intermediate-Range Nuclear Forces (INF) Treaty in 2019, citing Russian violations and China’s growing arsenal, while New START—the last remaining bilateral treaty, signed in 2010—expired in February 2026.[50]

Constructivist claims of a “nuclear taboo,” which posited that shared norms constrained the use of nuclear weapons, also came under strain.[51] Russia’s explicit nuclear threats following its 2022 invasion of Ukraine, combined with U.S. rhetorical warnings toward North Korea, seemed to validate realist expectations that material power ultimately prevails over normative restraint. In practice, Russia, China, and the United States have all moved to modernize their nuclear arsenals, underscoring the renewed salience of deterrence in an era of intensifying great-power rivalry.

 

Liberalism and Russia’s Invasion of Ukraine, 2014–Present 

Examining Russia’s actions in Ukraine from 2014 to 2022 through a liberal lens is equally instructive. Democratic peace theory suggests that Russia’s troubled democratization in the 1990s may have heightened the risk of conflict, as fledgling democracies are historically more prone to instability and war.[52] Liberal theorists emphasize that state preferences—shaped by domestic politics—matter as much as systemic power balances. From this perspective, Russia’s decision to invade Ukraine reflected domestic pressures and a nationalist conception of legitimacy threatened by the existence of a democratic, West-leaning Ukraine. The eastward spread of democracy thus appeared to Moscow not as benign, but as a direct challenge to its authority and influence.

Liberal intergovernmentalism offers a particularly incisive explanation for why the 2013–14 crisis became a breaking point. Andrew Moravcsik’s framework directs attention not to systemic pressures but to the domestic preference formation that precedes international bargaining.[53] By 2013, Putin’s domestic political coalition had consolidated around a nationalist narrative that framed closer Ukrainian ties with the European Union as a direct threat to Russian economic interests and political stability at home.[54] When Ukraine’s President Yanukovych, who was responsive to competing domestic pressures from pro-Russian eastern constituencies and oligarchic networks dependent on Russian trade, suspended the EU association agreement, the ensuing Maidan protests reflected a rival set of domestic preferences within Ukraine—ones that prioritized European integration, anticorruption reform, and civic nationalism.[55] Liberal intergovernmentalism thus reveals the 2014 crisis as a collision of incompatible domestic preference sets rather than a simple story of external great-power competition: Russia and Ukraine entered the bargaining arena with preferences already shaped by internal political economies that left little room for a negotiated outcome acceptable to both sides.

Yet, many other liberal predictions that should have constrained conflict failed to materialize.[56] Economic interdependence, prior security commitments to Ukraine, and the weight of international law all proved insufficient to deter Russian aggression. The reason, from a liberal intergovernmentalist standpoint, is instructive: where domestic preferences are already set against cooperation—as they were in Putin’s Russia by 2014—interdependence and institutional ties cannot override them. Neoliberal institutionalists could have argued that dense energy interdependence between Russia and Europe would raise the costs of conflict to prohibitive levels; in practice, Moscow calculated that those costs were acceptable given the domestic political stakes of allowing Ukraine to reorient toward the West. Efforts to integrate Russia into cooperative frameworks, such as NATO’s partnership programs, foundered on the same logic. Instead, Russia responded by asserting its prerogatives in its near abroad, demonstrating that liberal mechanisms of constraint operate only when the underlying domestic preference structures allow them to.

 

Constructivism and Russia’s Invasion of Ukraine, 2014–Present 

Reviewed through a constructivist lens, Russia’s actions in Ukraine reflect its socially constructed identity as a great power with a legitimate sphere of influence, particularly over former Soviet states. From this perspective, Ukraine’s pursuit of closer ties with NATO and the European Union represented more than material shifts in security or economic alignment; they directly challenged Russia’s self-conception and its preferred regional order.[57] Because states act on the basis of meanings they attach to others, a pro-Western Ukraine was redefined by Moscow not as a neighbor to be managed, but as an existential threat.[58] This reclassification transformed a relationship marked by competition into one of enmity, making cooperation difficult and heightening distrust—an outcome characteristic of a security dilemma.[59] 

Russia’s annexation of Crimea in 2014 and its full-scale invasion of Ukraine in 2022 can thus be understood as attempts to reaffirm its identity and impose a regional order consistent with its vision of the “near abroad.” These actions were not merely expressions of material power but efforts to reproduce and legitimize a particular understanding of sovereignty, hierarchy, and Russian centrality. Crucially, constructivism’s concept of constitutive power—the capacity to shape not just what other actors do, but who they are and what they want—is visible in how Russia sought to use coercive intervention to forestall Ukraine’s ongoing process of national identity formation. Moscow was not simply responding to a strategic threat; it was attempting to reconstitute Ukrainian identity in ways compatible with Russian regional dominance, refusing to recognize the legitimacy of a Ukrainian national self-conception oriented toward Europe. That this effort backfired—accelerating rather than arresting Ukrainian identification with Western norms and institutions—illustrates the contingent and contested nature of identity construction that constructivism emphasizes.[60] By framing its interventions as essential to self-preservation, Moscow challenged international norms of sovereignty and self-determination while reinforcing an adversarial “culture of anarchy” in which its security is defined through opposition to the West.[61]

 

Conclusion

International relations theories function as analytical frameworks and heuristics, offering structured ways to think about global dynamics and enabling practitioners to make recommendations or decisions quickly and effectively. These theories explain the world by emphasizing how the application of different elements of the global system, referred to as causal mechanisms, result in specific outcomes given certain conditions.

Realism highlights enduring patterns of power and competition, focusing on the core interest of survival and the primacy of states. Liberalism emphasizes institutions, interdependence, and domestic preferences, broadening the definition of interests to include economic prosperity, stability, and peaceful coexistence. Constructivism draws attention to the role of identities, norms, and meaning-making, arguing that security, anarchy, and threats are socially constructed through state interactions.

Crucially, the complexity of the global environment means that these theories necessarily simplify how states engage with and react to various, often opposing forces. As such, no single theory provides a complete picture, and “only rarely does a single factor determine the way politics will work out.”[62]

The central mandate for strategic leaders is to draw from a diverse toolkit of theories rather than relying on a single perspective. Cultivating this theoretical fluency is essential because it helps prevent biases and blind spots that may arise from viewing every situation through one narrow lens, a risk that can have serious consequences.

A fluid understanding of how these theories contrast and complement one another can help guide practitioners in making national policy decisions and formulating strategies to best promote national interests. Examining U.S.–Russia relations across the post–Cold War decades illustrates how the application of multiple theoretical perspectives reveals both the opportunities for cooperation and the recurring sources of conflict. Ultimately, theoretical fluency does not guarantee predictive certainty, but it does provide a richer, more nuanced understanding of international affairs and a stronger foundation for sound decision-making.  

 

Endnotes

About the Authors

Dr. Joel R. Hillison is a professor of national security studies at the U.S. Army War College. He publishes frequently on national security issues, specifically focused on Europe and NATO. Hillison earned a PhD in international relations from Temple University, a master’s in economics from the University of Oklahoma, and a master’s in strategic studies from the U.S. Army War College. He has more than 30 years of active service, including three years at NATO. His latest book, A Sustainable U.S. Strategy for Transatlantic Relations: NATO, the EU, and the USA, was published in November 2025.
https://orcid.org/0009-0009-0104-1561

Dr. Zenel Garcia is the associate dean and an associate professor at the U.S. Army War College, where he holds the Henry L. Stimson Chair of International and Military Studies. His research examines security and strategic studies, political economy, and processes of state and region-building, with a focus on China, the Indo-Pacific, and Eurasia.
https://orcid.org/0000-0002-4794-9200

Dr. M. L. deRaismes Combes is an associate professor of national security at the U.S. Army War College. Her research focuses on U.S. foreign policy, irregular warfare, and the Middle East, with a theoretical emphasis on identity, narratives, and ontological security. Dr. Combes holds a PhD in international relations from American University’s School of International Service and was a fellow at the University of Texas at Austin’s Clements Center for National Security. She is the author of the forthcoming book, Becoming the Stranger: American Identity and Security in the Shadow of 9/11.
https://orcid.org/0000-0002-9006-6892

 

The views expressed in this article are solely those of the author. They do not necessarily reflect the opinions of Marine Corps University, the U.S. Marine Corps, the Department of the Navy, or the U.S. government.