The Department of Defense is working on a new definition of irregular warfare, and the stakes are surprisingly high. The danger lies not just in forgetting whatever was learned from twenty years of engagement with substate actors through counterinsurgency and counterterrorism. Rather, in seeking to apply the term to state-based actors, the better to capture the subversive approach being used by America’s principal adversaries, there is a risk that irregular warfare will lose all its meaning. The issue is certainly not that irregular warfare is irrelevant to the strategic competition at hand—quite the contrary—but rather that the US military system is proving too traumatized by its counterinsurgency past, and too mired in its own orthodoxies, to grasp the contribution of the term. Before the value that irregular warfare provides is lost, an interrogation of its meaning is necessary. On this basis, this article sets out a reworked definition of irregular warfare, one that retains its crucial focus of on legitimacy, coercion, and political power but that is also applicable to interstate competition.

Why Redefine?

The Department of Defense officially defines irregular warfare as “a violent struggle among state and non-state actors for legitimacy and influence over the relevant population(s).” The term emerged from the challenges posed by nonstate armed groups, which necessarily engage in subversion and guile to outmaneuver militarily stronger states. In these efforts, mobilization, legitimacy, and credibility produce societal power, allowing adversaries weaker at the offset to paralyze stronger foes and, at times, prevail against seemingly impossible odds. Reflecting the approach, the official definition of irregular warfare specifies that it “favors indirect warfare and asymmetric warfare approaches” to direct military confrontation and seeks “to erode the adversary’s power, influence, and will” until a final military push, if necessary, can seal the deal.

Irregular warfare has always been a contested term, but it has served a valuable purpose to a military institution too often seduced by its own raw strength. Whatever the problems with the term, the effort to redefine it must therefore be taken on cautiously, lest its contribution is lost. Why, then, is this project officially being attempted? Four reasons come to mind.

First, there is concern that the definition of irregular warfare is too closely associated with insurgency and counterinsurgency, or with the types of major expeditionary efforts conducted in Afghanistan, Iraq, and elsewhere. Already, there is an effort to move from a “violent struggle . . . for legitimacy and influence over the relevant populations” to a “struggle . . . to influence populations and affect legitimacy”—a broader remit—because the former was seen as too centered on counterinsurgency. The question is whether this attempt to distance irregular warfare from the legacy of unpopular counterinsurgency operations is being undertaken for the sake of conceptual precision and utility or, more likely, because that legacy is now so toxic.

Second, there is a related concern that irregular warfare is too narrowly focused on struggles between state and nonstate actors and must therefore be tweaked to account for state-based adversaries that adopt similar approaches, those that lean on asymmetrical methods and indirect attack. The current definition does specify that irregular warfare occurs “among state and non-state actors,” and so there is technically sufficient space therein to fit state-on-state confrontation. On that basis, this reservation about the nature of the actors involved appears minor, but it does raise a bigger issue. Specifically, irregular warfare has always been concerned with struggles relating to intrastate schisms, which would appear insufficient if the intent now is to apply the term also to interstate competitions.

Third, there is an official feeling that the definition of irregular warfare is too closely tied to the question of violence, which may work within counterinsurgency contexts but fits badly to the subversive and illicit activities of states seeking to outdo rival governments. As a result, the Pentagon has in recent reworkings of the term elided the mention of violence as a definitional marker, a seemingly minor change but one that significantly extends what irregular warfare may describe. Going further, others take issue with the language of “warfare” and have mooted “irregular competition” as a way to prevent the militarization of threats that are not uniformly violent in nature. Such a move, it is hoped, might also bring in the interagency and international partners that all irregular warfare practitioners are desperate to involve but who see any type of warfare as beyond their remit.

Fourth, in the post-counterinsurgency era, there is a growing weariness with the focus within irregular warfare on legitimacy and the business of affecting popular perceptions. As irregular warfare comes to describe an ever-growing range of activity, more and more observers are questioning whether it must always, by definition, have legitimacy as its root—as its center of gravity. On the one hand, the critique is driven by the conceptual stretching that irregular warfare has undergone, but on the other hand it is steeped also in the aversion to any apparent hearts-and-minds philosophy following the collapse of a counterinsurgency doctrine predicated on similar ideals. In the wake of its perceived failure, some view a focus on legitimacy as unnecessarily idealistic and even as inappropriate within a context of hard-nosed power politics.


These urges are informing the effort to redefine irregular warfare, but their aggregate effect risks turning it into something very alien to its nature: a catchall for any state behavior that is subversive or manipulative but that does not amount to outright war.

The logic at hand is that states, much like insurgents, are behaving illicitly, ambiguously, or asymmetrically, but on a global scale, in order to offset their conventional military weakness versus the United States. This commonality of approach between insurgent and state adversaries has been central to the expansion of irregular warfare to define both, as the US military needed a lens through which to understand hostile and coercive state behavior that did not explicitly or transparently cross the threshold into war. Writing in Moscow in 1946, George Kennan famously cast the approach as “political warfare,” not a term he coined but which he rightly described as “the logical application of Clausewitz’s doctrine in time of peace.” The issue, however, is that while states can certainly be as conniving, as deceptive, and as subversive as insurgents, the overlap with irregular warfare as we knew it is too thin to warrant its wholesale importation into this new world.

Three problems become immediately clear. First, if the concern is state manipulation, subversion, or interference, why not just speak plainly of such behavior using precisely those terms? What is the added value of “irregular warfare” in explaining traditional (if illicit) forms of statecraft, particularly when response falls to agencies and instruments of state that typically have little to do with warfare? The use of illicit activities is not the definitional marker of irregular warfare within societies, and so why should it define irregular warfare among states? There has to be something more specific and narrower to allow this concept to be meaningful.

Second, the implied definitional point that irregular warfare occurs below the threshold of actual war makes the invocation of the “w” word all-the-more puzzling. Excluding violence from irregular warfare’s remit also removes from this term the very political violence that it has always sought to explain, be it by nonstate armed groups using all forms of violence, from terrorism to civil war, or even state efforts to conquer one another within a context of winning legitimacy and quashing dissent. Meanwhile, taking violence out of the equation makes it very difficult to distinguish between sharp-elbowed competition and irregular warfare. Where does the one end and the other start? As one indication of the ensuing confusion, the Joint Staff’s Office of Irregular Warfare was recently renamed to include also, in its title, “and Competition.” The conflation makes sense, given the spectrum of ways in which irregular strategies operate—from the kinetic to the nonkinetic—but it does not follow that irregular warfare is inherently limited to the latter.

Third, and most gravely, the attempt to distance legitimacy and credibility from the definition of irregular warfare robs the term of its unique contribution to strategic thinking. The danger here lies in turning irregular warfare into a study of tactics, losing sight of precisely why the approach is deployed: as a contest of legitimacy, with all else feeding into that. The central message of irregular warfare is that legitimacy can be translated into irresistible power. Legitimacy is why thousands of Ukrainians, even those based in the EU, are flooding back into that country to fight, all while Russians are leaving their country to avoid the same. Legitimacy is the target of all disinformation, manipulation, active measures, and terrorism that we associate with irregular warfare, because these efforts seek to erode the cohesion and resolve of set adversaries. Legitimacy is also at the root of societal and political resilience and to resistance efforts against stronger foes. Indeed, the focus on legitimacy is the most important component of irregular warfare. If it is lost, so is irregular warfare.

Crucially, the struggle for legitimacy is no popularity contest. As Stathis Kalyvas explains with reference to “geographical loyalty,” raw power can readily override political and social preferences. Those who wield control—those who decide who lives or dies—can usually produce the compliance they seek. Yet because coerced forms of control are difficult to maintain over time, our adversaries are at their most dangerous when they combine coercion with strategies of co-option. In a similar vein, it should always have been realized that winning hearts and minds necessarily includes more than being liked, namely shaping the subject’s behavior and preferences through the application of all relevant sources of power. In contrast to the caricaturesque understanding of this term that was allowed to dominate most counterinsurgency discussion, the point was always to blend power with co-option in a way that appealed both to hearts (sentiments of support) and minds (calculation of interest). A similar duality applies to legitimacy.

A Way Forward

In one strong sense, irregular warfare is already irredeemable. The term is defined in contradistinction to “traditional warfare,” a flawed heuristic that betrays the ahistorical and narrow character of much official thinking within the military. And yet, ironically for this very reason, irregular warfare has significant utility in reminding us, especially the Department of Defense, of just how wars typically unfold and how power is decided. We might just be better off speaking of war as war and eschewing artificial delineations between conventional and irregular operations, but not so long as terminological asceticism implies the reductive understanding of war typical of military institutions. Despite its many flaws, then, irregular warfare seems likely to stay, and we therefore face the challenge of grasping its relevance to the strategic competition currently faced by the United States.

That irregular warfare is indeed relevant to understanding and countering the strategies imposed by Russia, China, and the like is beyond doubt. Russia has engaged in interstate irregular warfare since at least 1917 and will presumably revert to kind given the poor returns achieved through conventional warfare in Ukraine. China also boasts extensive experience with irregular warfare, which it now uses to upend the international system formed following World War II. On a smaller scale, Iran and North Korea have demonstrated their proficiency with irregular warfare, which has allowed them to sponsor state and nonstate proxies, amass regional power, and increase their influence. Cuba and Vietnam did likewise. That these states have adopted nonstate-like strategies should not surprise, in that their approaches are all rooted within each country’s foundation through successful insurgency. It is puzzling, and unfortunate, that despite being formed through similar circumstances, the United States has so resolutely forgotten the lessons of its past.

But what does it mean for a state to conduct irregular warfare? How can this term be helpful in unpacking what the United States is facing and in mounting a response? Drawing on our recent research, our argument is for a return to basics, so that irregular warfare can regain its intended meaning and be applied more expressly to this new strategic context. In narrowing the field of options that “irregular warfare” can helpfully describe, it is true that the utility of the term may seem diminished. Ironically, it is precisely through such conservativism that irregular warfare survives, because a concept that describes virtually everything is also good for virtually nothing.

On this basis, a few principles emerge. First, irregular warfare is inherently about intrasocietal schisms. Irregular warfare describes the mobilization of some against others, so as to allow a militarily weaker actor to gain power at the expense of a stronger adversary. Where direct approaches are deemed too hazardous, energy and verve are found by attacking the foundations of the status quo and creating a new world, and new norms, that the powers that be cannot resist. Much as any other type of warfare, irregular warfare is fundamentally about politics, as actors struggle over the right to lead.

Second, violence, or at least coercion, is inherent to irregular warfare, as it distinguishes this type of approach from sharp-elbowed competition, such as that one may find even in democratic party politics. Coercion can range from low-level violence or even threats thereof to outright combat in service of an irregular warfare strategy, as seen in the Vietnam War, in Colombia’s struggle against FARC (Fuerzas Armadas Revolucionarias de Colombia), or even in Russia’s ongoing conventional assault on Ukraine—given its broad targeting of the legitimacy of that state; Russia’s reliance, alongside force, on more indirect and asymmetric types of attack; and the strategic clash therein between contending worldviews and narratives. Logically, the presence or threat of coercion is a necessary ingredient, given the description of the whole as a form of warfare.

Third, the chief definitional criterion of irregular warfare is its strategic intent: to erode or build legitimacy and influence. Methods may vary over time—they may span the direct and the indirect, the kinetic and the nonviolent—but the totality of the project is irregular if it is grounded in a struggle for legitimacy. The issue must be engaged with at this strategic level, in terms of its objective, as it is the intent that informs the nature of subsidiary actions taken, be they seemingly unwarlike or clearly belligerent. When an insurgent group is distributing aid or providing medical services, it is for the same strategic reason that it engages in terrorism and violent attack—to contest legitimacy and forge a path to victory. When it quietly and nonviolently mobilizes societal support, it is to assist the eventual seizure of power. The broader project, and intent, is irregular warfare.

Fourth, given the above parameters, state use of irregular warfare becomes something far more precise than a general sense of competing. Specifically, states use irregular warfare when they seek to accentuate (or mitigate) the schisms in targeted societies, thereby to gain power and influence. Offensively, this type of approach might entail sponsoring terrorism and insurgency abroad, engaging in election interference to subvert democratic integrity or to stoke social conflict, or undermining the legitimacy of a state so that a rival actor can rise up. Defensively, the challenge lies in how to react and how to guard against such actions. On the whole, this view of state-based engagement takes us back to two key missions of irregular warfare—foreign internal defense and unconventional warfare, respectively about fostering resilience and empowering resistance. The overriding context for such activity, however, is the competition for legitimacy in which these actors are embroiled, with foreign actors stoking the fire in their own ways.

Fifth, one can, strictly by analogy, conceive of a broader interpretation of irregular warfare as a global competition of legitimacy, whereby a country seeks power by accentuating the schisms between different world orders. International society then becomes the equivalent of domestic society, with states and actors assuming the role of its population. Thus, much as thinkers like David Kilcullen and James A. Bates saw within al-Qaeda’s efforts a “global insurgency,” it is possible to view China as involved in a global campaign of irregular warfare—a multifaceted, international offensive that weaponizes all normal instruments of power, everything from diplomacy to economic levers, and integrates them with kinetic menace and direct application. From this vantage point, the Communist Chinese Party is on a global quest to reshape international society much as it did with Chinese society back in 1949, and via strikingly similar means.

Mercifully, outright violence has so far been absent from the Chinese approach, which instead features growing economic ties, investment and loans, along with generous servings of disinformation, subversion, and threats. Still, these efforts can helpfully be framed as irregular warfare on a global scale, with the foregoing nonviolent efforts cast as but the shaping phase for a later military face-off with the United States, a confrontation that might not even be needed if US resolve can be so sapped during peacetime that it refuses the fight even when its core interests are at stake. Certainly, a country such as Taiwan is already keenly aware of this playbook. China’s expansion into the South China Sea has been largely nonviolent, relying instead on civilian and economic efforts, although it is rooted in a common awareness of the military realities at hand. In securing territory along with trade and communications routes, China is also positioning itself for an eventual attack on Taiwan, either threatened or carried out when necessary. Even if violence is kept at bay, coercion can prove a formidable weapon.

If it is our perception that China is launching a similar effort against the United States, the strategic objective provides the necessary context to classify constituent actions as part of this irregular warfare campaign. One may then see components of the overall struggle in how China weaponizes dependence on its economic support, in its resulting lack of transparency in trade negotiations, in its unchecked engagement in illegal activities (ranging from illegal fishing to usage of corruption and organized crime), and in its deft control of what can be said and done internationally about its domestic politics. The point of these activities can then be viewed through the prism of a competition for legitimacy, but at a global level, with US credibility and appeal targeted to clear the way for the Chinese takeover. Crucially, this lens retains the focus on the strategic objective and theory of victory—and defines tactics accordingly. The alternative, to begin with the toolkit of tactics and see them as “irregular warfare,” misses the forest for the trees.

Conclusion: A New Definition

The principles laid out above provide the blueprint for a new definition: “Irregular warfare is a coercive struggle that erodes or builds legitimacy for the purpose of political power. It blends disparate lines of effort to create an integrated attack on societies and their political institutions. It weaponizes frames and narratives to affect credibility and resolve, and it exploits societal vulnerabilities to fuel political change. As such, states engaged in, or confronted with, irregular warfare must bring all elements of power to bear under their national political leadership.”

This proposed definition of irregular warfare respects the etiology of the term and, thus, the reasons for its coinage; but it also applies it to a new strategic environment. It retains the lessons of two decades of involvement in irregular warfare yet allows for the internationalization of irregular struggles within a global competition for power. In seeking to redeem irregular warfare, it does not demilitarize the term, but instead insists on coercion as a component of the whole, thereby justifying its martial connotations and giving the armed forces a natural role to play. In its crucial retention of legitimacy as the center of gravity, however, it also strongly implies that whatever the Department of Defense can do to help must be in support of civilian actors and political strategies.

Left to resolve, then, is this striking contradiction raised by irregular warfare in practice, namely the great difficulty of authorizing, resourcing, and mobilizing the instruments of statecraft necessary for its prosecution. At present, there is no civilian operational system into which to emplace irregular warfare as defined: with exceedingly few exceptions, there is no civilian replica for the military’s doctrine, organization, institutionalized intellectual efforts, and operational templates to prosecute this mission. Indeed, there is also no culture, outside of the military, to do organized, troops-to-task thinking about security, however broadly defined. Until this reality is addressed, irregular warfare—intellectually as well as in practice—will fall to the same community within the Department of Defense, with scant impact on the broader system responsible both for assessment and response. Might the redefinition of irregular warfare, if properly handled, spur the necessary change?

David H. Ucko (@daviducko) is professor and chair of the War & Conflict Studies Department at the College of International Security Affairs, National Defense University. He is an adjunct professor at Johns Hopkins University and a senior visiting fellow at the Department of War Studies, King’s College London.

Dr. Thomas A. Marks is a distinguished professor and serves as the Major General Edward G. Lansdale chair of irregular warfighting strategy at the College of International Security Affairs, National Defense University.

This article draws in part on the second edition of Crafting Strategy for Irregular Warfare: A Framework for Analysis and Action (Washington, DC: NDU Press, 2022), which was published earlier this month.

The views expressed are those of the authors and do not reflect the official position of the United States Military Academy, National Defense University, Department of the Army, Department of Defense, or United States government.

Image credit: 1st Lt. Benjamin Haulenbeek, US Army