About a decade ago, hybrid warfare made its big breakthrough. The concept had been around for a number of years, but few people knew what it meant and even fewer seemed to care. In 2014, Russia launched the opening act of its ongoing war of aggression against Ukraine, taking control of the Crimean Peninsula. It did so through a combination of different means, including military force, disinformation, economic pressure, nuclear blackmail and obfuscation. Moscow’s synergistic use of a diverse range of instruments seemed like a perfect illustration of hybridity. All of a sudden, talk about hybrid warfare and hybrid threats became the rage.
Dismissed as an academic fad by some and as an obstacle to clear strategic thinking by others, the initial appeal of hybridity has faded somewhat since 2014. However, the idea remains alive in public discourse. Just in course of the last few days, Finnish President Alexander Stubb described recent incidents in the Baltic Sea as a form of ‘hybrid influence’; the leaders of eight European nations tasked former NATO Secretary General Jens Stoltenberg with preparing a report on advancing Nordic-Baltic security and defence cooperation, including to counter ‘hybrid acts and operations’; and European Commissioner for Equality, Preparedness and Crisis Management Hadja Lahbib spoke about ‘hybrid threats’ in the context of misinformation.
Many lawyers, myself included, were puzzled when the term first rose to prominence. Hybridity is not a legal concept, that much was clear. State officials and others were talking about it, so it seemed to be a thing. But what were its legal implications, if any? What areas of law were even relevant here? Did it raise any proper legal issues or was it just hot air?
A fair amount of effort has gone into answering these questions and to explore the legal aspects of hybrid threats. The International Committee of the Red Cross (ICRC) has added its voice to these debates in its 2024 Report on International Humanitarian Law and the Challenges of Contemporary Armed Conflicts. An excerpt from that Report was published on this blog to other day in a post by Samit D’Cunha, Tristan Ferraro and Tilman Rodenhäuser.
In their post, D’Cunha, Ferraro and Rodenhäuser make a simple, but very important point: the political narratives surrounding hybridity and related concepts such as grey zone conflict must not obscure the question of conflict classification and displace the application of the law of armed conflict. They are exactly right. Whether or not an armed conflict exists must be determined with reference to the rules of the law of armed conflict. Notions such as hybrid warfare and grey zone conflict are not helpful or even relevant in this respect. More generally, D’Cunha, Ferraro and Rodenhäuser also suggest that describing situations as war or warfare ‘when they do not, in fact, amount to armed conflict risks adding fuel to the fire’. On this point, they do not quite hit the nail on its head, as there is a bit more going on here. To explain, it is helpful to offer a brief conceptual overview of hybridity and grey zone conflict, before highlighting some of the legal and strategic dynamics involved.
Framings of Hybridity and Grey Zone Conflict
As there is no consensus definition of hybridity in the field of international security, it is useful to distinguish between three main framings of the notion. In 2005, James Mattis and Frank Hoffman, both of the United States Marine Corps, coined the phrase ‘hybrid war’ to describe the shape of future warfare. According to Mattis and Hoffman, future adversaries were likely to combine distinct forms of violence, including conventional warfighting, terrorism, insurgency, guerrilla tactics and organized criminality, to offset the superior conventional capabilities of the United States. Mattis and Hoffman described this blend of different modalities of violence as ‘hybrid war’.
In subsequent years, NATO embraced the idea of hybridity, but did so by focusing on hybrid threats posed by adversaries ‘with the ability to simultaneously employ conventional and non-conventional means adaptively in pursuit of their objectives’ (NATO, Bi-SC Input, 2010). This extended the notion of hybridity beyond actual warfighting to cover situations of potential violence and those involving the combined use of military and civilian instruments. In response to Russia’s annexation of Crimea, NATO leaders thus signaled their readiness to ‘address the specific challenges posed by hybrid warfare threats, where a wide range of overt and covert military, paramilitary, and civilian measures are employed in a highly integrated design’.
The third framing of hybridity as ‘hybrid threats’ is concerned with the synergistic use of mostly non-violent means below the threshold of open hostilities. Since most foreign policy is ‘hybrid’ in the sense that all actors aspire to use the different instruments at their disposal in a complementary manner, the hybrid threat construct relies heavily on its ‘threat’ element to distinguish Statecraft as practiced by Western nations from that of their rivals. Accordingly, in recent years, the term hybrid threats has been used primarily as a pejorative label to describe the activities undertaken by autocratic regimes to undermine or otherwise harm democratic nations, in particular by targeting their vulnerabilities and influencing their decision-making process within the wider context of geopolitical competition.
The different framings of hybridity overlap to some extent with the concept of grey zone conflict. Whereas hybridity is concerned mostly with the diverse instruments and tactics that hostile actors employ, the grey zone concept focuses primarily on the space where competitive interactions with such actors take place. The grey zone is often described as a space between war and peace that is distinct from both. The notion thus divides international relations into three spheres: war at the top end, peace at the lower end, with the grey zone in the middle. This tripartite division rests on the idea that war and peace are separated by a distinct zone characterized by confrontations that are more aggressive than ‘normal’ peacetime competition, but which fall short of open hostilities as seen in war. This grey zone exists because geopolitical rivals carefully calibrate their action on the international stage to achieve the greatest strategic impact without, however, handing their adversaries a casus belli, so as to avoid escalation into open military confrontation.
Speaking politics to law
The different framings of hybridity and the notion of grey zone conflict are best understood as heuristic devices that shine a spotlight on certain features and manifestations of contemporary conflict and geopolitical rivalry. They are not, however, full-blown theories of international relations, strategy, war or anything else. Keeping this in mind helps a lot.
Nor are they legal terms of art, as already noted. Take grey zone conflict, for example. Proponents of the concept often suggest that it illustrates how the dividing line between war and peace has become increasingly blurred. To most international lawyers, this sounds ahistorical and archaic in about equal measure.
As is well known, before the era of the United Nations Charter, international law drew a sharp and formal distinction between the state of war and the state of peace. However, this seemingly clean normative framework masked the fact that States and international lawyers were unable to reach agreement on how these two legal conditions, war and peace, should be distinguished from one another. Moreover, whatever international law said on the subject, the world was an unruly place, bursting at the seams with ‘limited war’, ‘imperial policing’, gunboat diplomacy, ‘frontier wars’ and other uses of force that did not fit neatly into the black and white categories of war and peace, at least as commonly experienced and understood. In any event, international law has left these debates behind in 1945. Today, the operative legal thresholds are no longer those of war and peace, but the ‘use of force’, ‘armed attack’, ‘self-defence’ and the existence of an international or non-international armed conflict. This matters, because the preoccupation with the supposedly blurred line between war and peace obscures the fact that international law draws the relevant thresholds in a different place. This not only overlooks the fact that the applicable rules are more flexible than is often assumed, but it also fuels a misguided perception that the law itself is badly outdated.
Against this background, we may read D’Cunha, Ferraro and Rodenhäuser’s post as a welcome reminder—presumably most useful to those who are not legal experts—not to fall into the trap of assuming, without proper legal analysis, that cases of hybrid warfare, hybrid threats and grey zone conflict amount to an armed conflict. However, this is not the only lesson here.
There is much loose talk these days about various forms of warfare, such as information warfare, political warfare, financial warfare, media warfare, energy warfare and legal warfare. None of these involve combat operations, which inspired by Clausewitz we may take to be the essence of ‘real’ war. Instead, in all of these cases, the warfare label is purely metaphorical. But why so? The obvious explanation is that the label is intended to underline the intensity of the antagonism involved. It reflects, in other words, the idea that information, finance, energy and even the law may be weaponized and used as instruments of strategic confrontation. Even though these forms of metaphorical warfare do not involve combat, they may still inflict significant harm on those targeted by them. Moving beyond metaphorical warfare, hostile actors may also cause significant harm through acts of violence other than combat. One example is the recent concern over the sabotage of critical infrastructure.
While none of the cases just mentioned are likely to amount to an armed conflict, we should not forget that the law of armed conflict is not the only relevant regime of international law in this context. Regard must also be had to the rules governing the use of force. In fact, in situations that involve violence other than combat between opposing armed forces, those rules are likely to be more relevant than the law of armed conflict. Thus, it is reasonable to ask whether a State engaged in a campaign to deliberately damage the maritime infrastructure of another State is using force within the meaning of the United Nations Charter. And if so, at what point does that use of force give rise to the right to respond with counterforce?
On closer inspection, much of what comes under the heading of hybrid warfare, hybrid threats and grey zone conflict turns out to raise quite significant legal questions. These include threshold questions: for instance, do certain activities amount to the use of force? China’s grey zone actions in the South China Sea are a prime example. They include questions of scope: what forms of misinformation are caught by the principle of non-intervention? They involve questions about legal gaps: what legal authorities may coastal States rely on to protect submarine communication cables in their exclusive economic zones and beyond?
Conclusion
The point to take away is that the relationship between hybrid warfare, hybrid threats and grey zone conflict on the one side and the law on the other is not a one-way street.
This should be obvious, but it is worth repeating that not everything that is labelled as warfare actually amounts to an armed conflict in a legal sense. Nor should we get carried away with metaphorical forms of warfare more generally: being a mighty information warrior on social media is not the same as defending a trench against an advancing enemy formation. The dividing line between participants and bystanders in modern warfare may be under pressure, but it has not dissolved into thin air. Conversely, not describing the use of military force as war, or calling it by another name, does not prevent it from qualifying as an armed conflict, should it meet the relevant criteria under the law of armed conflict, as set out with admirable clarity by D’Cunha, Ferraro and Rodenhäuser.
At the same time, we cannot hide behind the existing legal categories and cross our fingers that something is not war or warfare unless and until the law of armed conflict says so. The growing importance of non-kinetic forms of harm casts doubt on the traditional view that physical violence is the essence of war, while the diffusion of real warfare across time, space and various functional domains undermines the classic duality of war and peace. This challenges our understanding of what war, in a colloquial sense, is and what it is not, which in turn puts pressure on the relevant legal thresholds and categories of international law. This is not to suggest that we should adapt the rules to reflect a more unruly world; perhaps our efforts need to focus on making that unruly world conform to the ideals reflected in our rules. At any rate, rather than looking at hybrid warfare, hybrid threats and grey zone conflict as notions that distract from the well-established legal criteria for determining the existence of an armed conflict, as D’Cunha, Ferraro and Rodenhäuser seem to imply, we may also take them as an invitation to reflect on what they tell us about the changing character of war and its implications for international law.
