Research Reports
The Conceptualization of Irregular Warfare in Europe

The Conceptualization of Irregular Warfare in Europe

Authors: Dr. Sandor Fabian and Gabrielle Kennedy

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This report is the first in a series of volumes in which the Irregular Warfare Center (IWC) explores the commonalities and differences of the conceptualization of irregular warfare across U.S. allies and partners. This initial volume compares and contrasts this conceptualization among five European academic institutions: the Netherlands Defence Academy, the Norwegian Defence Research Establishment, the Swedish Defence University, the European Centre of Excellence for Countering Hybrid Threats, and the Military Academy of Lithuania. Each of these institutions replied to surveys the IWC designed, assessing how these institutions individually conceptualize and teach irregular warfare and related concepts.

This report should be of interest to defense and foreign policy decision makers, practitioners and scholars in the United States and allied and partner nations, the media, defense industry representatives and non-governmental organizations, and others concerned about the challenges associated with irregular warfare. As irregular warfare becomes institutionalized “as a core competency with sufficient, enduring capabilities to advance national security objectives across the spectrum of competition and conflict,” in accordance with the Irregular Warfare Annex to the 2020 National Defense Strategy, the IWC’s role in U.S. national security solidifies.1 The annex notes that though the United States has conducted continuous irregular warfare against violent extremists on a global scale, the current primary national security challenge, which the annex calls strategic competition, requires mastery of irregular warfare at a different level. The annex calls for innovative ideas and new means of employing existing capabilities, as well as improving interagency and international cooperation. A clear avenue for IWC’s utility is in the international cooperation and information sharing that will yield success in countering irregular warfare.

In the current international system, the United States and its allies and partners face similar irregular threats, making the IWC’s involvement in the international dialogue on irregular warfare a major part of its mission. A current challenge in such conversation is that U.S. allied and partner nations hold their own set of ideas regarding the definition of irregular warfare, current irregular threats that require the most attention, and appropriate reaction to such irregular threats. Understanding and potentially bridging the gaps between the conceptualization of irregular warfare on the part of the United States and allied and partner nations is a key first step to future cooperation and greater resiliency in the face of irregular threats. This report serves as the IWC’s first offering on international collaboration aimed at understanding the differences and potential points of cooperation in conceptualizations of irregular warfare.

Executive Summary

As the Irregular Warfare Annex to the 2020 National Defense Strategy suggests, the character and form of war are constantly changing. The requirement for mastery of irregular warfare persists. To maintain critical competencies, develop new capabilities, and improve interoperability, continued study of irregular warfare must remain a high priority. This study is a precursory step to cooperation needed to meet such competency requirements. Its goal is to highlight areas of commonality and difference in the conceptualization of irregular warfare in European institutions. This is an instrumental first step in identifying a baseline knowledge of how certain institutions of interest think of irregular warfare, solidifying areas of potential cooperation on issues relevant to irregular warfare.

The report finds that there is no overarching or consistent definition used among surveyed institutions in Europe. This trend trails through other findings, such as the lack of codified threats, the lack of institutionalized education on irregular warfare, and limited publicly available research on relevant topics. Most of the participating institutions are tied to special operations research or preparation, displaying the broader link between special operations forces and irregular warfare curriculum. This linkage is bolstered by the idea that these forces are considered as either the primary tool of irregular warfare or a major component in the practice.

On a more granular level, the report finds that geography impacts conceptualization of irregular warfare. Proximity to Russia correlates with the use of the term hybrid warfare in the place of the term irregular warfare. Institutions located in countries closer to Russia seem to prefer more defensive conceptualization and tend to focus on countering Russian malign activities. The geographical, institutional, and general definitional trends found through this study allow this study an application broader than the institutions studied.


The IWC is the primary driver of developing the Department of Defense’s (DoD) understanding of irregular warfare. The IWC aims to better integrate concepts related to irregular warfare into national defense strategy and operational planning by fostering collaboration and developing a unified effort across the DoD, the U.S. interagency, and multinational partners. Advancing the DoD’s understanding of irregular warfare concepts and doctrine in collaboration with key allies and partners is a major component of such efforts. The IWC also aims to create a community of interest centered around irregular warfare and related concepts to develop a diverse set of IW methodologies, allowing the United States and relevant allies and partners to address future irregular threats more effectively. Additionally, the IWC identifies current and future irregular threats and supports the development of effective countermeasures.

This project is a reflection of cooperation with U.S. partners and allies on issues related to irregular warfare (IW). Indeed, such cooperation is a primary driver of the IWC’s goals and efforts. This project compiles and analyzes granular details of how key European institutions conceptualize irregular warfare, understand irregular threats, and teach IW-related concepts. The insights contained herein illuminate the similarities and differences in thought of key European institutions on irregular warfare, yielding a more informed path toward cooperation for the U.S. and its partners and allies. This is a vital component to establishing the path for future avenues of deeper cooperation on irregular warfare-related issues and the joint development of optionality in terms of addressing irregular threats. Both of these things are crucial for intellectual interoperability on irregular warfare topics, which is a major part of the IWC’s mission.


The research driving this report stems from a survey and subsequent semi-structured interviews with selected representatives of five European institutions. The overall project was conducted between 1 November 2022 and 20 January 2023. The survey was conducted between 1 November 2022 and 15 January 2023. The in-depth semi-structured interviews were conducted between 15 November 2022 and 20 January 2023. The survey questions addressed the target institution’s conceptualization of irregular warfare; which irregular threats the institution considers and prioritizes; how the institution teaches concepts related to irregular warfare; whether the institution publishes on the topic; the level of the institution’s connection to a broader community focused on irregular warfare; and who makes up the institution’s faculty, courses, and target audience. The responses to survey questions directly shaped the interview portion of the research, providing potential avenues of further exploration in the interviews. The report itself is broken into two sections: a report of the study, assessing each institution and its responses, and an analysis section, discussing the similarities and differences in thought regarding irregular warfare found through participants’ responses. When reporting on each institution’s survey and interview responses, this report strives to utilize language that is as close as possible to how the institution itself responded to preserve fidelity to the original answers of the respondent. Several themes arose from the survey and the interviews, serving as guidance for future areas of cooperation or potential areas of contention between the United States and European partners in the realm of irregular warfare.

The five institutions that participated were specifically selected to ensure sufficient variation in the sample while maximizing response quality. The investigation was conducted at the Netherlands Defence Academy, the Norwegian Defence Research Establishment, the Swedish Defence University, the European Centre of Excellence for Countering Hybrid Threats, and the Military Academy of Lithuania. The goal of the case selection was to harvest data from institutions with different levels, purposes, and training audiences while ensuring geographical dispersion within Europe.

The Netherlands Defence Academy

The War Studies Research Centre (WSRC) is part of the Faculty of Military Sciences at the Netherlands Defence Academy, the only academic institution in the Netherlands that offers military-related education and performs research related to military topics.2 The Netherlands Defence Academy has provided military leadership training to Dutch military forces since 1828 and teaches civilians and military personnel alike.3 The WSRC employs a multidisciplinary approach to assessing war and warfare with a primary focus on contemporary conflict. Several sections that are key to contemporary warfare make this multidisciplinary approach possible.

These sections include cyber security and cyber operations, intelligence and security, international security studies, military history and strategy, military law, military police operations, and military-operational sciences.4 Comprising these sections are 60 researchers, making up one of the largest academic war studies communities in Western Europe.5

The key to the WSRC’s mission is bridging the gap between experts from various fields. The WSRC engages academic researchers, policymakers, military professionals, civil society, and anyone with an interest in the study of war and peace. Bringing subject matter experts together through conferences and symposiums is a major part of this effort. Most notable is the Future of War conference, held in joint effort by the WSRC and the Changing Character of War Research Centre at the University of Oxford.6 In addition to this event, the WSRC disseminates its key research findings through public lectures and published papers.

Definition of irregular warfare

The definition of irregular warfare that the War Studies Research Centre uses is dynamic. The department largely bases its definition of irregular warfare on U.S. conceptions of the topic. Key faculty members of the WSRC credit this decision to both the partnership between the Netherlands and the United States and the influence of U.S. doctrine and literature on the Western irregular warfare research community. Specifically, the conceptualization of irregular warfare relies on the thoughts of American scholar James Kiras and the 2010 Joint Operating Concept of Irregular Warfare from the U.S. Department of Defense. With this in mind, the respondent notes that the conceptualization of irregular warfare reflects a U.S. vantage point and is not reflective of ideas and views that are specific to Europe. The respondent notes that, in the short term, it is crucial to construct a common understanding of irregular warfare; in the long term, it is crucial that Europe and its allies use a common understanding in their efforts related to irregular warfare.

The full definition of irregular warfare provided by the respondent is from the work of Martijn Kitzen, the chair of the Irregular Warfare and Special Operations at the Netherlands Defence Academy. The definition reads:

“…a violent struggle involving non-state actors (including violent armed groups acting as state proxies) and states with the purpose of establishing power, control, and legitimacy over relevant populations. Due to military asymmetry and the political nature of the struggle, the use of force mostly takes unconventional or unorthodox forms and is typically combined with other, non- kinetic, activities. As such, irregular warfare favors an indirect approach that does not focus on military defeat, but on winning the population(s) at stake and eroding the opponent’s will… .”7

According to Kitzen, defining irregular warfare establishes the differences between irregular warfare and more traditional means of waging war, showing the utility of creating means of training and waging irregular warfare that are separate from traditional conventions.

The respondent asserts that irregular warfare is warfare and that there is a false dichotomy between irregular warfare and traditional warfare. Rather than accepting the idea that irregular warfare is categorically different from traditional warfare, it is most beneficial to think of the concept as existing on a continuum of different ways to counter opponents and wage wars. Furthermore, the definition of irregular warfare should not focus on responding to a single adversary but should rather be able to encapsulate the tactics of different opponents and the ever-changing geopolitical sphere.

Identified irregular threats

Though there is not a prioritized list, the threats that the War Studies Research Centre’s research focuses on include Russian and Chinese gray zone aggression, terrorism, and insurgencies. The department is especially concerned about insurgencies that aim to destabilize countries in the “ring of instability” surrounding Europe. These interests align closely with the goals and concerns of the Netherlands Ministry of Defence and the Ministry of Foreign Affairs. The two ministries are especially concerned about terrorism, insurgency, cyberattacks, information and influence operations, and attacks on seabed infrastructure. These threats should be addressed with a comprehensive and whole-of-society approach.

Teaching irregular warfare concepts

The War Studies Research Centre at the Netherlands Defence Academy teaches irregular warfare concepts at several different levels. Although there is no specific IW curricula, IW-related topics and concepts are taught in the initial cadet training at the bachelor’s level, as part of the staff college, in the graduate program in Military Strategic Studies at the master’s level, and at the doctoral level comprised mostly of soldier-scholars. On the topic of the approach taken in teaching concepts related to irregular warfare, the program acknowledges that it uses a focus on U.S. doctrine and literature. This limits the use and understanding of opposing or different approaches to the topic. Because of this, the program works to include adversaries’ conceptualization and employment of irregular warfare to create a more robust and well-rounded education on the topic of irregular warfare. The WSRC does publish in multiple outlets and publications on the topic of irregular warfare. The target audience of this work is typically scholars and practitioners.

Norwegian Defence Research Establishment

The Norwegian Defence Research Establishment (FFI) is the primary Norwegian institution that conducts research and development initiatives related to defense. Partnered closely with Norway’s military organizations, FFI is the chief adviser on defense-related science and technology innovations to the Norwegian Ministry of Defence and the Norwegian Armed Forces’ military organization.8 In order to effectively accomplish this, FFI recognizes the importance of international cooperation and collaborates with other scientific institutions and members of industry at both the national and international levels. FFI participates in several expert groups in the NATO Science and Technology Organization and in the European Defence Agency.9 In addition to this, FFI holds cooperation agreements with the Netherlands, the United Kingdom, France, and the United States.10

FFI comprises five research divisions: Defence Systems; Strategic Analyses and Joint Systems; Sensor and Surveillance Systems; Total Defence; and Innovation and Industrial Development.11 Much of the work done in these divisions aligns with the goals and initiatives of the Norwegian Armed Forces or those of institutions with whom FFI partners. FFI utilizes an applied research approach to provide analysis, contract research, and advising to the Norwegian Armed Forces and civil society institutions.12

Definition of irregular warfare

FFI defines irregular warfare in its simplest form as the type of actions that results from tasks that conventional forces cannot effectively accomplish, requiring the deployment of special forces. Specifically, irregular warfare is a military or paramilitary operation that is conducted in a hostile or politically sensitive environment to achieve objectives that require the use of capabilities for which there is no conventional need. Major distinctions between irregular warfare and conventional operations can be seen in the degree of physical and political risk, operational techniques, the method of application used, the degree of independence of friendly support, and the degree of dependence on detailed intelligence and local advantages.

FFI characterizes irregular warfare as a complex issue with many qualifications that are not all definite. In some cases, irregular warfare is an activity between conventional forces and intelligence forces. In other scenarios, irregular warfare is the use of state represented forces to subdue non-state actors, or the use of state represented forces to support smaller resistance forces to “disturb” an adversary and prepare for the use of conventional forces. Indirect and asymmetric approaches to warfare that are used to erode an opponent’s will, power, strength, or influence are also categorized as irregular warfare. With a broad approach to the topic, the respondent warns that irregular warfare is often confused with unconventional warfare, stabilization, military assistance, counterterrorism, and counterinsurgency practices. FFI characterizes irregular warfare as a joint capability, not a unique, stand-alone one. Leaders at FFI view irregular warfare as existing along a continuum, with some situations calling for more irregular tactics and other situations calling for more conventional tactics. To FFI, special forces are key to irregular warfare practices, and the combination of conventional forces and special forces is key to a successful military operation. The Norwegian concept of irregular warfare is primarily focused on countering Russian activities.

Identified irregular threats

The DIME acronym (diplomatic, informational, military, and economic) is commonly used in the field of international relations to describe tools that can be used to assert power and influence. FFI adopts this concept. Informational, military, and economic threats all describe what FFI finds relevant to irregular warfare. In terms of informational threats, FFI is concerned about influence operations, disinformation and misinformation from state and non-state actors alike, and soft power approaches used to “win hearts and minds” and cultivate goodwill. Military threats relevant to irregular warfare include Russian military activity in Ukraine and in the Arctic. Lastly, FFI is particularly concerned with economic threats that target the energy sector, such as the destruction of gas pipelines or disruptions to power supplies. At least two of these threats must be occurring from the same actor simultaneously for the activity to be considered hybrid. Hybrid activity is difficult to identify, making it difficult to convince politicians and society of its existence. This makes countering these threats more difficult.

Teaching irregular warfare concepts

Topics related to irregular warfare are not regularly taught at FFI. Irregular warfare is treated as a national and international issue that can be integrated into other portions of curriculum. Topics related to irregular or hybrid warfare are most commonly taught through individual lessons at the command and staff college level and the general staff college level. Using similar thought in teaching and in practice, FFI characterizes irregular warfare as an added capability to conventional warfare, not as a fully integrated portion of military practices that complements traditional warfare. FFI does publish on irregular warfare, but the publications are rarely unclassified and are typically written to benefit the Norwegian special forces.

Swedish Defence University

The Centre of Special Operations Research (CSOR) was established in 2021 at the Swedish Defence University.13 The Swedish Defence University was originally founded as an institution for specialized higher military education within the Swedish Armed Forces. However, it now operates independently as a higher education institution of all degree levels for civilians and military officers alike. CSOR is housed within the Department of War Studies and Military History, alongside eight divisions: Functions and Perspective Division, Military History Division, Languages Division, Air Operations Division, Maritime Operations Division, Land Operations Division, Joint Warfare Division, and Strategy Division.

CSOR also works as a virtual link between the Swedish Defence University and the Swedish Armed Forces Special Operations Command. CSOR was created to formalize and organize the activities already being done at

the Swedish Defence University in support of the Swedish special forces.14 CSOR enables staff at the Swedish Defence University to coordinate activities, develop international networks, collaborate with other entities, and increase the speed and efficiency at which support to the special forces is provided.15 Chaired by Professor Alastair Finlan, who teaches at the Swedish Defence University, the advisory board of CSOR is made up of several key members of the defense industry in Sweden. Members include Vice Admiral Jonas Haggren, head of the Swedish Armed Forces; Annika Nordgren Christensen, member of the board of the Swedish Defence University and the Royal Academy of War Sciences; James Kiras, professor at the School of Advanced Air and Space Studies in the United States; and Dr. Byron Harper, deputy director of the NATO Special Operations Headquarters. The head of CSOR is Ulrica Pettersson, a senior lecturer in War Studies at the Swedish Defence University.

Definition of irregular warfare

CSOR does not utilize one definition of irregular warfare. This is primarily due to the fact that leaders of CSOR have not identified a definition in use that does not include foreign internal defense, which is not as applicable to small European states. The respondent does see utility in developing a more specialized definition of irregular warfare for small states, especially in the shadow of Russian and Chinese activities within Europe.

Identified irregular threats

Threats meet the threshold of irregular warfare when conventional forces are unable or unprepared to counter the threat posed. There is no prioritized list due to CSOR’s dynamic view of irregular warfare. Because irregular threats are those that are unexpected, the ability to react and think quickly would be lost, should a prioritized list be made.

Teaching irregular warfare concepts

Irregular warfare is taught on a practical level and through a special operations lens at the Swedish Defence University. The example provided by the respondent was one in which students studied theory and then applied learned principles through a field trip to the sabotage trail at a heavy water factory in Norway. Questions for student thought and study revolve around how the same mission could be accomplished today with the technological advances made.

The Swedish Defence University does publish on the topic of irregular warfare. Perhaps the most notable publication was the Resistance Operating Concept (ROC), published jointly by the Swedish Defence University and Special Operations Command Europe (SOCEUR). The Swedish Defence University has also published articles on resistance and the definition of “threshold.”

The European Centre of Excellence for Countering Hybrid Threats

The European Centre of Excellence for Countering Hybrid Threats (Hybrid CoE) is an autonomous international organization that promotes the need to counter hybrid threats through a whole-of-government and whole-of-society approach.16 Hybrid CoE is hosted in

Finland and closely cooperates with NATO and the EU. While 32 states are currently participants of Hybrid CoE, activities hosted by Hybrid CoE are open to all countries that are part of the EU and NATO.17 Hybrid CoE’s primary aim is to build the capabilities of its participating states and organizations in order to prevent and counter hybrid threats.18 Participants operate across different sectors, governments, and states, creating a diverse network.

Hybrid CoE hosts activities covering a wide array of topics across societal, governmental, and military domains. Hybrid CoE is the only organization in which both the EU and NATO work and conduct exercises together.19 The Hybrid CoE hosts activities centered on sharing best practices, providing recommendations, testing new ideas and approaches, training practitioners, producing a wide range of publications, and organizing hands-on experiences for participating states and organizations. There are three communities of interest networks (COI) operating as divisions for Hybrid CoE: Hybrid Influence, Vulnerabilities and Resilience, and Strategy and Defense.20 These COI are key to accomplishing Hybrid CoE’s mission, providing an opportunity for multinational and multidisciplinary sharing of ideas and experiences between participants.

Definition of irregular warfare

The term irregular warfare exists primarily in the realm of military action and is typically coupled with concepts related to counterinsurgency. In particular, irregular warfare is normally associated with NATO military missions occurring beyond the territory of NATO members because of Europe’s relative security until 2014.

Hybrid CoE classifies irregular warfare as the use of military tools under the threshold of open conventional military confrontation. However, Hybrid CoE conceptualizes irregular warfare as a subset of hybrid warfare, which is noted as the antithesis of the western concept of war. Hybrid CoE distinguishes hybrid warfare and irregular warfare through the scope of actions that are classified under each term. The nature of hybrid warfare is broader in that hybrid warfare encapsulates attacks on decision-making processes and uses leaders as targets. On the other hand, irregular warfare focuses on population-centered attacks. The incentive to use hybrid warfare stems primarily from an objective to degrade or disturb democratic societies. Because of this asymmetric connotation of hybrid warfare, and thus irregular warfare, the respondent noted that democracies do not typically use hybrid warfare outside of the scope of an acute conflict.

In terms of conceptualizing hybrid warfare and countering the threats it poses, Hybrid CoE’s approach reaches beyond the multi-domain or even broader state-driven conceptualization. Instead, Hybrid CoE adds a societal approach in opposition to the use of only the military realm to think about such topics. A societal approach to conceptualize irregular warfare is useful to Hybrid CoE because of the diversity in European strategic culture and because of the strong divide between internal and external security affairs. This division causes military vocabulary like “warfare” to be excluded from describing security events happening internally, therefore limiting the applications of countering hybrid warfare when only using a military lens to assess possible solutions.

Identified irregular threats

Hybrid CoE has identified and published over 35 threat vectors in 13 different domains. The applications of these threat vectors are designed specifically for the particular targets that are meant to be addressed. Because of this, there is no prioritized list of irregular warfare threats that are routinely followed by Hybrid CoE. Instead, current events and the impact of hybrid warfare threats drive the direction of Hybrid CoE’s work. Russian aggression and subversive tactics are a current focus. A gray zone created by the West through allowing malicious actors to push the boundaries without punishment, coupled with Western subversion in other conflicts since the end of the cold war has emboldened Russia and allowed further aggression.

Due to the fact that one single hybrid or irregular warfare campaign can host a multitude of different threat vectors, hybrid threats should be addressed and considered in a holistic manner. Hybrid CoE focuses on understanding the way that different attack vectors interact and coexist, in turn allowing for the study of response mechanisms from participating Hybrid CoE countries.

Teaching irregular warfare concepts

Hybrid CoE typically teaches remotely and offers training events tailored to specific countries and training audiences. Audiences are typically made up of all sectors of society. Irregular warfare is taught by several different lecturers and in lecture series. Some course examples include: 101 on Hybrid Threats, Countering Electoral Interference Training, and Deterrence TTXs. Due to the high flexibility and morphing potential of topics related to hybrid and irregular warfare, courses related to these subjects are adopted in accordance with the target group. On a more granular level, the understanding and teaching of hybrid threats is largely based on the conceptual model, “Landscape of Hybrid Threats,” that was developed by Hybrid CoE with the EU Joint Research Centre.

Hybrid CoE solely publishes papers related to hybrid threats and warfare matters. There are about 50 publications annually. Most of what is published is written by Hybrid CoE staff, with some of the work commissioned out to high-level experts in the field Though Hybrid CoE does have a strategic focus, it is able to react to global developments in almost real time and publish on those topics quickly. The target audience for these publications is decision makers and practitioners in participating states, NATO and EU staff, politicians of all levels, government civilians and military officials, and academic audiences, including students.

Military Academy of Lithuania

The Military Academy of Lithuania combines traditional university studies with military training. The Military Academy of Lithuania holds several different courses for the Lithuanian military and one course on basic warfare for civil servants.21 In addition to this, the Academy hosts bachelors, masters, and doctoral studies programs on military and defense topics.22 As an internationally recognized university for national security, defense, and military studies, the Military Academy of Lithuania also hosts several research groups.23 These groups facilitate international cooperation on high-level international research projects, as well as housing research and “experimental development” relevant to the Lithuanian national defense system.24

Cooperation partners of the Military Academy of Lithuania include public institutions, non-governmental organizations, and foreign military training establishments. Exchange programs between cadets at the Military Academy of Lithuania and foreign cadets are hosted regularly, with some courses offered to certain foreign militaries on a need-based schedule. Most recently, the Military Academy of Lithuania provided a commander training course to Ukrainian cadets in November 2022.25 As a regular point of cooperation with foreign militaries, the Military Academy of Lithuania participates in the annual Baltic Sea Military Academies Conference. In addition to this, the Military Academy of Lithuania is involved in initiatives like EU COE for Countering Hybrid Threat and EU Hybrid Fusion Cell, showing the breadth of the Academy’s international networks and initiatives. Domestically, the Military Academy of Lithuania cooperates with nearly all Lithuanian institutions of higher education on research, teaching, and conferences.

Definition of irregular warfare

Rather than use the term irregular warfare, the respondent used hybrid warfare. Neither Lithuania as a state nor the Lithuanian national defense system has a single, unified definition of hybrid warfare or the threats associated with it. However, the Military Academy of Lithuania recognizes activities existing below the threshold of conventional military confrontation as hybrid warfare. Though not officially endorsed by the Lithuanian defense system’s legal staff and not included in national strategic level documents, there is a working definition of hybrid warfare used by those who study the topic. The guidelines set by the European Union and NATO are the prevailing concepts adopted by the Military Academy of Lithuania since memberships, concepts, and activities of these institutions dictate activities of the Military Academy of Lithuania. NATO’s conception of hybrid warfare rests on the idea that hybrid methods are deployed to blur the lines between war and peace and target citizens to sow doubt surrounding the target government. Hybrid threats typically combine military and non-military action through covert and overt means. Examples provided by “NATO’s response to hybrid threats” include disinformation, cyberattacks, economic pressure, deployment of irregular armed groups, and the use of conventional military forces.26 Additionally, the aforementioned concept of irregular and hybrid threats developed by Hybrid CoE significantly influences the Military Academy of Lithuania’s thinking on the topic.

Identified irregular threats

The Military Academy of Lithuania exclusively focuses on Russian malign activities. The only proactive activities from the Military Academy of Lithuania are aligned with exposing Russia’s malicious actions to the international community and punishing Russia in accordance with international law. With this being said, the Military Academy of Lithuania does not believe that Russia has a grand strategy for its use of hybrid warfare. Instead, Russian hybrid activities are viewed as a collection of interrelated opportunistic actions that are used to create favorable conditions and achieve political goals. Disinformation, information warfare, and propaganda are the hybrid threats most emphasized by Lithuania at the national level. However, cyber security, energy security, intelligence, economic threats, and kinetic operations like military exercises are also of increased concern to Lithuania. The frequency at which these threats occur, the visibility of the threat, the measurability of the threat, and the presence of specific capabilities in the Lithuanian national defense system all impact how much attention is given to one particular hybrid threat.

Responses to hybrid threats are complex, requiring the work of different sections of government. The respondent provided the example of the artificial migrant flow created by Belarus. The hybrid attack, which was induced by the influx of illegal immigrants due to the actions from the authoritarian regime of Belarus, provided the basis for the Lithuanian Ministry of the Interior to develop a plan of measures to combat hybrid threats. This example of a hybrid threat, along with information operation threats stressed at Lithuania’s national level, display the breadth of hybrid warfare’s range of threats. One challenge here, however, is the difficulty in convincing politicians, private sector actors, and society writ large about the existence of hybrid threats and activities. This, coupled with the isolation self-imposed by different sectors when it comes to problem-solving, makes cross-sector coordination and collaboration difficult.

Teaching irregular warfare concepts

While the Military Academy of Lithuania does not have a separate course dedicated to hybrid warfare or hybrid threats for undergraduate or graduate students, several different departments do host separate courses on related topics. The Political Science Department at the Academy does host courses like international and national security, Russian war studies, propaganda and information war studies, and terrorism studies. In addition, in 2022, this department established a military history course on Modern Campaigning and Irregular Warfare for ERASMUS cadets. This new course examines four campaigns from an irregular warfare perspective. Management programs have courses on national security, cyber security, informational warfare, and intelligence. Public security programs hold courses on international and national security, individual and public security, counterterrorism and organized groups, information security, energy security, and intelligence.

Courses include lectures or sections of lectures on the concept of hybrid warfare and hybrid threats. The Academy uses the idea that hybrid warfare is a preparation phase before conventional warfare is ultimately used. Researchers at the Military Academy of Lithuania study a variety of unconventional threats; the studies are typically published in the Lithuanian Annual Strategic Review and the Journal of Security and Sustainability Issues, which are the two Lithuanian journals dedicated to the study of national and international security. Much of the work done by the Military Academy of Lithuania is intended for the national defense system in the form of policy papers, policy briefs, and research studies with recommendations, making much of it unavailable to the public.

In terms of irregular or hybrid warfare topics taught as part of military education, Vytautas the Great Army Command and Staff Course (ACSC), the Air Force Command and Staff Course (AFCSC), Commander and Junior Staff Officer Course (CJSOC) and other courses do not have dedicated lectures or modules for the concept of hybrid warfare. However, the courses hold lectures on topics such as information security, energy security, intelligence, Russia’s strategy towards Baltic states, and China’s strategy toward Europe.

Beginning next year, the Military Academy of Lithuania will organize a Hybrid Threat Resilience course for national defense system personnel. A similar course was piloted in 2022 by the Military Academy of Lithuania for Ministry of Defense (MoD) staff in conjunction with the MoD Hybrid Threat Resilience Group and the Hybrid CoE. A portion of the content taught in this course will come from the research projects done under MoD national projects “Societal Resilience to Hybrid Threats” and “Democratic Resilience in Defense Policy: National Approaches in the Neighborhood of Aggressive Russia.” Content from these projects will be coupled with lectures by the MoD Hybrid Threat Resilience Group specialists to form the course.

Commonalities, Differences, and Implications

Definition of irregular warfare

European institutions are not unified in thought regarding irregular warfare. There is no universally accepted definition of irregular warfare across the European institutions surveyed, even on a foundational level.

For some institutions, like the Military Academy of Lithuania for example, a lack of an institutional concrete definition of irregular warfare stems from there being no concrete definition of the term across the state as a whole. One consistent assertion throughout many of the responses is the idea that irregular warfare exists below the threshold of conventional warfare, insinuating that warfare exists on a sort of continuum. The tone of this assertion, however, varies from institution to institution. Some look at irregular warfare as part of the conflict/ competition spectrum, while others look at irregular warfare as activities unique to special forces. In addition, institutions view the prerequisites for an activity to be deemed “irregular” differently. For example, the Military Academy of Lithuania says that hybrid activities exist below the threshold of conventional warfare and are used to blur the lines between war and peace, making the action of engaging in hybrid/irregular warfare a more active choice for the threat actor. On the other hand, the Swedish Defence University says that threats can be characterized as irregular when conventional forces are unable or unprepared to counter the threat posed, making the target country’s response type the determinant in whether or not a threat is irregular.

Irregular warfare threat landscape

There is also no unified irregular threat landscape across European institutions. Instead, irregular threats given most attention are driven by the individual strategic environments of an institution. Furthermore, no institution studied has a prioritized list of irregular threats and threat actors, whether this be by design or by practicality due to the ever-changing threat environment and need for specific response for each threat vector. While many of the respondents named specific threat actors and relevant threats when asked about irregular threats, FFI has adopted the DIME acronym to describe specific types of threats that meet the criteria for irregular qualification, and used examples of Russian aggression to explain the DIME acronym. Russian aggression or subversion was mentioned in nearly all of the responses, signaling that this is a common interest despite institutional hesitation to name specific prioritized threats. That said, some institutions are more concerned with Russian hybrid activities than others, determined by proximity of the institution to Russia. This is exemplified by the Military Academy of Lithuania’s sole dedication to Russian malign activity and the institutional use of the term hybrid warfare instead of irregular warfare by many institutions with proximity to Russia. On the other hand, institutions of countries farther away from Russia tend to use the U.S. conceptualization of irregular warfare and associated threats. No matter the threat specified, irregular and hybrid warfare seem to be reactive and exclusively focus on countering malign activities.

Teaching irregular warfare concepts

Similar to the lack of a concrete, unified definition or method to assess irregular threat, the European institutions studied do not have any sort of institutionalized education on the topic of irregular warfare. There are some lessons within existing professional military education and some stand-alone courses within professional military education. However, this is not consistent across the institutions studied, with some of them, like FFI, not regularly teaching irregular warfare concepts at all. While most of the institutions teach irregular warfare-related concepts at the theoretical level, one institution, the Swedish Defence University, mentioned teaching irregular warfare concepts through a special operations lens with a heavier focus on the practical level. While there is no real cohesion in irregular warfare education across the institutions studied, there is a clear linkage between

special operations forces and the study of irregular warfare concepts, as many of the institutions studied have ties to special operations forces or teach students linked to that area of defense. In more outward-facing action, the institutions do publish on irregular warfare-related topics, like cyber warfare, influence campaigns, and threats to critical infrastructure for example. However, the relevant publications primarily focus on individual topics subordinate to irregular warfare, rather than dedicate themselves to the study of irregular warfare as a whole. Publications put out by the institutions studied are not always available to the public, depending on the institution’s target audience. Some institutions published for policy makers and practitioners, some included academia in the target audience, and some operate almost solely to fulfil the needs of the relevant special operations command.


Without understanding the conceptualization of irregular warfare in key institutions beyond the borders of the United States, the path toward cooperation that is so crucial to countering irregular warfare is more difficult to traverse. The IWC plays an integral role in establishing the foundation for this cooperation. Empowered by the Irregular Warfare Annex to the 2020 National Defense Strategy, a major effort of the IWC is working toward more effective international cooperation on relevant topics through establishing key areas of commonality and difference in key international partners’ conceptualization and use of relevant topics in coursework. This report, which provides an outline of relevant European institutions’ ideas related to irregular warfare, is a product of the effort to build up international cooperation on topics related to irregular warfare.

The responses of European institutions interviewed and surveyed reveal that there is no unified conceptualization of irregular warfare in Europe. With no consistent idea of what irregular warfare is at the foundational level, there is little continuity in the ways in which the institutions of interest assess irregular threats and teach related concepts. The link between special operations forces and the study of irregular warfare is one commonality between several of the institutions. From a basic level, the understanding of irregular warfare is correlated to geographic location; the study shows that the more proximate an institution is to Russia, the more likely it will use the term hybrid warfare instead of irregular warfare. In addition to this, there is no institutionalized teaching of irregular warfare among institutions studied. Despite the lack of continuity in thought and practice, identification of Russian malign activities as irregular threats by several institutions and the reactive nature of irregular warfare are common themes throughout the studied institutions.

The major implication of these findings is that, in the longer term, a common way to conceptualize irregular warfare is a necessary step toward solid international cooperation. In the short term, understanding the discontinuity in irregular warfare conceptualization, categorization of potentially irregular threats and methods, and teaching of relevant topics throughout European institutions is key to operationalizing the first step. Beyond this, understanding the nuances in these areas will aid interested parties in fostering efficient communication and streamlined cooperation on topics related to irregular warfare. A major part of gaining this understanding is not only international academic cooperation, but also fusing the academic community with military thinkers and leadership found at institutions like those studied to develop a more comprehensive understanding of irregular warfare and associated threats. This type of cooperation and integration will facilitate not only a more cohesive idea of what irregular warfare is and what related threats look like but will also create a more informed international coalition on the topic and improve intellectual interoperability. Irregular warfare mastery will not come from rushing to define irregular warfare, but rather from the fulsome and deep cooperation necessary to conceptualizing the topic fully.


  1. “Irregular Warfare Annex to the National Defense Strategy,” 2020. Oct/02/2002510472/-1/-1/0/Irregular-Warfare-Annex-to-the-National-Defense-Strategy-Summary.PDF.
  2. Faculteit Militaire Wetenschappen. “War Studies,” December 8, 2020. cms/view/be190201-bd05-4401-9373-afdb6df71776/war-studies.
  3. “Netherlands Defence Academy – Defensie.Nl.” Onderwerp. Ministerie van Defensie, March 16, 2015. https://
  4. Faculteit Militaire Wetenschappen. “War Studies,” December 8, 2020. cms/view/be190201-bd05-4401-9373-afdb6df71776/war-studies.
  5. “War Studies Research Centre (WSRC).” warstudiesresearchcentre/?originalSubdomain=nl.
  6. Faculteit Militaire Wetenschappen. “The Future of War,” February 14, 2022. https://
  7. Kitzen, Martijn. “Operations in Irregular Warfare.” Handbook of Military Sciences, edited by Anders McD Sookermany, 1–21. Cham: Springer International Publishing, 2020. 4_81-1.
  8. Norsk. “Forsvarets forskningsinstitutt (FFI).”
  9. “Cooperation – Optimal Use of Resources.”–optimal-use-of- resources.
  10. Ibid.
  11. “The Division for Defence Systems at the FFI.”
  12. Ibid.
  13. “The Centre of Special Operations Research (CSOR).” sedu/organisation/specialised-centres/the-centre-of-special-operations-research-csor.html.
  14. Ibid.
  15. “New Centre for Research on Specialised Units.” Text. Accessed February 24, 2023. swedish-defence-university/news/2021-06-23-new-centre-for-research-on-specialised-units.html.
  16. Hybrid CoE – The European Centre of Excellence for Countering Hybrid Threats. “What Is Hybrid CoE?” https://
  17. Ibid.
  18. Ibid.
  19. Ibid.
  20. Hybrid CoE – The European Centre of Excellence for Countering Hybrid Threats. “Hybrid Threats.” https://www.
  21. “Courses.”
  22. “University Studies.”
  23. “Research Groups.”
  24. “Research Groups.”
  25. Nair, Shalini. “Lithuania Delivers Commander Training Course to Ukrainian Cadets.” Army Technology (blog), November 4, 2022. cadets/.
  26. NATO. “NATO’s Response to Hybrid Threats.” NATO.