Grey Zone Warfare as Strategy: Ambiguity, Risk Management, and the Erosion of Order

Grey zone warfare is not new. What is new is the role it now plays at the strategic level. Tactics that once sat at the margins of international politics have moved to its centre, shaping how states compete, coerce, and manage risk without crossing the threshold of open war.

In a recent episode of The International Risk Podcast, Dr Andrew Mumford, Professor of War Studies at the University of Nottingham, argues that this shift represents more than a semantic debate about labels such as hybrid warfare or sub-threshold conflict. It reflects a deeper transformation in how power is exercised in an environment defined by risk aversion, legal ambiguity, and political constraint.

As Dr Mumford puts it, grey zone activity has “never before attained a strategic level of importance” nor been used “with this regularity” in a way that is now shaping geopolitics itself. Understanding why requires moving beyond surface descriptions of cyber attacks or disinformation campaigns and toward the logic that binds them together.

From episodic tactics to strategic environment

Hybrid and irregular methods have always existed alongside conventional warfare. History offers countless examples of insurgency, proxy conflict, and deniable violence coexisting with large-scale war. What distinguishes the contemporary grey zone is not novelty but centrality.

According to Dr Mumford, these tactics have migrated from supporting roles to become primary instruments of statecraft. States increasingly rely on them not as supplements to conventional power, but as alternatives to it. This reflects a world in which the political, economic, and reputational costs of open conflict have risen sharply, while the incentives to influence outcomes without escalation remain strong.

The result is a strategic environment where pressure is applied continuously rather than episodically. Security is eroded incrementally rather than shattered decisively. Conflict becomes persistent, ambiguous, and difficult to attribute, yet no less consequential for that.

Ambiguity as design, not by-product

At the heart of grey zone warfare lies ambiguity. Not as an accidental feature, but as a deliberate design choice.

Dr Mumford stresses that ambiguity is the central characteristic of hybrid conflict because it allows states to act while constraining the responses of others. By obscuring attribution and operating below legal thresholds, states force their adversaries into a dilemma. Respond too forcefully, and risk appearing escalatory or illegitimate. Respond too weakly, and invite further encroachment.

This dynamic is often described through the metaphor of salami slicing, a gradual accumulation of small actions that individually appear manageable but collectively alter the strategic balance. Whether cutting undersea cables, probing airspace, interfering with elections, or exploiting maritime law, the objective is not immediate victory but sustained erosion.

Crucially, ambiguity does not require plausibility to be effective. As the example of Crimea demonstrates, deniability need only be sufficient to delay decision-making and fracture consensus. In such cases, ambiguity functions less as concealment and more as strategic friction.

The maritime domain as a grey zone laboratory

The maritime environment has emerged as one of the most fertile spaces for grey zone activity. Its vastness, complex jurisdictional regimes, and dependence on civilian infrastructure create ideal conditions for deniable interference.

Dr Mumford highlights cases ranging from fishing vessels repurposed for intelligence collection to suspicious activity around undersea cables and pipelines. These actions exploit the blurred boundaries between civilian and military assets, between commerce and security, and between accident and intent.

The implications extend far beyond naval strategy. Roughly 98 percent of global digital communications rely on undersea cable networks. Interference in this domain threatens not only national security but economic continuity and social stability. Yet responding militarily to such acts is rarely feasible or proportionate, reinforcing the asymmetry that grey zone tactics are designed to exploit.

Deterrence without thresholds

Traditional deterrence theory assumes clarity. Clear actors, clear red lines, and clear consequences. Grey zone warfare systematically undermines all three.

As Dr Mumford notes, deterring an adversary who does not wish to be seen acting is inherently problematic. Deterrence by punishment relies on attribution. Deterrence by denial relies on resilience. In the grey zone, both are difficult to achieve at scale.

The result is an environment in which escalation ladders are unclear and conventional deterrence logic struggles to adapt. Cyber attacks, election interference, and infrastructure sabotage do not map neatly onto military responses. Responding in kind is often impractical, particularly when states are attacked precisely in areas where they are more vulnerable than their adversaries.

This does not mean deterrence is obsolete, but it does mean it must be rethought. The absence of a single catalytic moment for grey zone warfare has allowed its effects to accumulate gradually, normalising a condition of permanent contestation.

Resilience as strategic currency

If deterrence is weakened, resilience becomes the critical counterweight. Dr Mumford is clear that resilience cannot be confined to government or military institutions. Grey zone warfare targets societies, values, and trust as much as territory.

Disinformation campaigns exemplify this shift. Their objective is not simply to mislead, but to corrode confidence in institutions and media, widening the gap between governments and citizens. Research discussed by Dr Mumford highlights a correlation between media literacy and trust in government, underscoring how societal factors shape strategic vulnerability.

This reframes security as a whole-of-society challenge. Infrastructure robustness, public trust, information literacy, and institutional credibility become components of national defence. In this sense, resilience operates as deterrence by reducing the effectiveness of grey zone tactics rather than threatening retaliation.

Proxy warfare and the management of risk

Grey zone activity also intersects with the resurgence of proxy warfare. Dr Mumford situates this trend in the aftermath of Iraq and Afghanistan, where the political and economic costs of large-scale intervention reshaped Western strategic thinking.

Rather than abandoning strategic interests, states shifted toward indirect approaches. Training, arming, and enabling local partners allowed influence to be exerted without the visible costs of occupation or regime change. This approach cuts across administrations and ideologies, reflecting a broader turn toward warfare as risk management.

Yet proxy strategies carry their own risks. Legal ambiguity, limited oversight, and unintended escalation remain persistent challenges. More importantly, they further entrench the logic of indirect conflict that defines the grey zone, blurring the boundary between war and competition.

Business, infrastructure, and strategic exposure

One of the clearest conclusions of the discussion is the extent to which businesses are now embedded in the strategic landscape. Grey zone warfare collapses the traditional separation between state security and commercial activity.

Multinational firms, logistics providers, telecommunications companies, and energy operators are increasingly targeted not despite their civilian status, but because of it. Their infrastructure is essential, visible, and often less protected than military assets.

Dr Mumford argues that businesses no longer have the luxury of viewing geopolitical risk as external. Public-private cooperation, information sharing, and resilience planning are no longer optional. In a hyper-connected world, a disruption in one sector cascades rapidly across others.

A permanent condition, not a temporary phase

Grey zone warfare is not a transitional phenomenon on the way back to conventional conflict. It reflects a durable adaptation to a world of constrained escalation, heightened risk sensitivity, and interconnected vulnerability.

As Dr Mumford observes, states turn to indirect warfare when the risks of direct action are perceived as too high. In that sense, grey zone conflict is less a failure of restraint than an expression of it. It is warfare adapted to political reality.

The challenge for policymakers, businesses, and societies is not simply to counter individual tactics, but to recognise the structural environment in which they operate. The grey zone is no longer an exception to international politics. It is increasingly its default setting.