The theoretical foundation of the analysis rests on the classical triad of deterrence: capability, credibility and communication. Capability means survivable second-strike forces, typically a triad of land-based intercontinental ballistic missiles, submarine-launched ballistic missiles and strategic bombers. Credibility exists when an adversary believes retaliation will actually follow if a red line is crossed, a belief shaped by doctrine, political will and alliance obligations. Communication involves signaling what behavior is unacceptable while preserving useful ambiguity. During the Cold War, mutual assured destruction anchored these three elements in a bipolar standoff with clearly constructed escalation ladders. Today, the study argues, asymmetrical arsenals, emerging technologies and cross-domain interactions have stretched deterrence far beyond simple mutual assured destruction toward concepts of flexible response and tailored deterrence.

Hybrid warfare, as defined in the review following Frank Hoffman’s framework, is the coordinated use of conventional force, cyber operations, disinformation, economic coercion, proxy forces and legal manipulation, or lawfare, to achieve strategic objectives without formally declaring war. Its subset, gray-zone activity, deliberately blurs attribution, escalation and the distinction between state and non-state actors. The author distinguishes the two with concrete examples: Russia’s 2014 annexation of Crimea involved hybrid tools such as deniable forces and cyber-attacks but crossed into conventional military operations once troops entered the peninsula, whereas the 2017 NotPetya cyber-attack achieved destructive effect without any physical incursion, remaining firmly in the gray zone. What makes contemporary hybrid warfare distinctive is not novelty, since propaganda and proxy wars are ancient instruments of statecraft, but the speed and coordination that digital technologies enable.

The central theoretical claim is that nuclear deterrence casts a shadow under which hybrid competition flourishes through three mechanisms. First, the perceived risks of escalation prevent direct military confrontation between nuclear powers. Second, a credibility gap opens between nuclear threats and hybrid actions: threatening nuclear retaliation against a cyber intrusion or an election interference campaign appears disproportionate and therefore incredible. Third, the cumulative effect of many individually minor sub-threshold actions can shift regional balances of power without ever triggering escalation. This is a modern extension of the stability-instability paradox first articulated by Glenn Snyder, which held that strategic nuclear stability permits lower levels of conflict. The review argues the paradox has become more pronounced in the hybrid era, and that adversaries increasingly operate in realms where nuclear threats are neither credible nor proportionate.

The empirical cases are drawn from Ukraine, NATO’s eastern flank and the Indo-Pacific. The war in Ukraine is presented as the most demanding test: nuclear deterrence did not prevent Russia’s conventional invasion of February 2022, but it has constrained direct combat between Russia and NATO. Russian nuclear signaling, including public references to strategic forces, has sought to limit Western intervention, while NATO members have supplied Ukraine with military, financial and intelligence support without direct intervention, demonstrating calibrated escalation management. The absence of direct NATO-Russia combat suggests deterrence remains structurally intact, while the ongoing large-scale conventional war shows it cannot stop sub-nuclear conflict when core interests are perceived to be at stake. The study also notes that Western sanctions, cyber activity and intelligence sharing constitute hybrid instruments in their own right, underscoring the author’s deliberately symmetrical treatment of all major powers.

The United States case illustrates how a nuclear umbrella enables cyber coercion. The Stuxnet malware, developed jointly with Israel and deployed against Iranian nuclear centrifuges between 2009 and 2010, physically destroyed roughly a thousand centrifuges and set back Iran’s program by an estimated eighteen to twenty-four months without prompting an overt military response. The review argues Iran’s restraint reflected an assessment that escalating beyond a cyber operation under the American nuclear umbrella was unacceptable. The 2022 US Nuclear Posture Review explicitly identifies strategic competition below the nuclear threshold as the principal threat, and the doctrine of tailored deterrence seeks response options across the full spectrum of conflict, though critics such as James Acton warn that blurring conventional and nuclear distinctions raises the risk of miscalculation.

Russia, holding roughly 5,580 warheads with 1,674 deployed on strategic delivery systems, explicitly frames nuclear weapons in its doctrine as means of escalation management, and its 2020 nuclear deterrence principles widened the conditions under which nuclear use might be considered. This ambiguity raises escalation thresholds in the adversary’s mind while Moscow conducts conventional and hybrid operations beneath them. The NotPetya attack, attributed to Russian military intelligence by US, British and Dutch agencies and causing more than ten billion dollars in global damage, drew sanctions and diplomatic expulsions but no military response, which the review interprets as evidence that nuclear deterrence shields even the most destructive hybrid operations from conventional retaliation. China presents a different profile: a rapidly expanding arsenal projected to grow from roughly 350 warheads in 2020 to nearly 1,500 by 2035, a declared no-first-use policy, and gray-zone coercion through maritime militia operations such as the 2012 Scarborough Shoal confrontation, where state-coordinated civilian vessels denied Philippine access without triggering a military response.

Several structural findings sharpen the analysis. Attribution ambiguity, the inability to identify a hybrid attacker in near real time, undermines deterrent signaling because threats cannot credibly be directed at an unconfirmed actor. Cumulative coercion aggregates sub-threshold incidents, each too minor to justify retaliation, into a strategic shift. Perhaps most dangerously, cyber operations against early-warning systems, command-and-control networks or dual-use satellites create entanglement risks: if a state believes its nuclear deterrent is compromised, it may adopt more aggressive launch postures, raising the probability of escalation through miscalculation rather than intent. Meanwhile, the collapse of the arms control architecture, including the 2002 withdrawal from the ABM Treaty, the 2019 demise of the INF Treaty and the expiration of New START in 2026, has removed verification mechanisms, transparency and crisis communication channels that once reduced the likelihood of miscalculation.

The review also challenges the assumption that democracies are structurally constrained in hybrid competition. The 2003 invasion of Iraq, launched despite mass public opposition and without UN Security Council authorization, and covert cyber and drone operations conducted with limited accountability demonstrate that democratic institutions shape but do not prevent coercive action. Conversely, authoritarian regimes face their own constraints: Russia must manage coalitions with China and India, while China balances regional assertiveness against economic stability. The author concludes that the democracy-autocracy distinction is an analytical failure for assessing nuclear signaling and hybrid behavior, and that credibility is better evaluated through strategic culture, alliance commitments and domestic political structure. Credibility itself has become a multi-domain, dynamic property, resting not only on warhead counts but on political coherence, narrative control and alliance cohesion, all of which hybrid disinformation campaigns deliberately target.

The policy prescriptions follow directly from the diagnosis. Rebuilding strategic stability requires renewed arms control, even limited agreements on notification and data exchange, plus confidence-building measures against cyber interference in nuclear command systems. Deterrence by denial deserves priority at sub-nuclear levels: cyber resilience, electoral protection, critical infrastructure hardening, information literacy and economic diversification all raise the cost of gray-zone operations without escalating risk. Crisis communication channels, transparency in military exercises, and international norms prohibiting cyber interference with nuclear command structures would reduce the danger of inadvertent escalation. The study proposes an integrated cross-domain model combining nuclear credibility, political legitimacy, alliance cohesion and societal resilience. Its conclusion is sobering but precise: nuclear deterrence is neither obsolete nor absolute. It remains structurally powerful as a ceiling on total war, yet operationally constrained beneath that ceiling, and the struggle for influence among the great powers will increasingly be decided in the ambiguous, cumulative and deniable forms of competition that flourish in its shadow.

Subject of Research: The effectiveness of nuclear deterrence against hybrid and gray-zone warfare among major powers

Article Title: Nuclear deterrence in the age of hybrid warfare

Article References: Edmond, C. (2026). Nuclear deterrence in the age of hybrid warfare. Discover Global Society, 4(1), Article 228. https://doi.org/10.1007/s44282-026-00419-1

Image Credits: AI Generated

DOI: 10.1007/s44282-026-00419-1

Keywords: nuclear deterrence, hybrid warfare, gray zone, strategic stability, stability-instability paradox, cross-domain deterrence, arms control, escalation, cyber operations, Russia, China, NATO

The timing of the review is no accident. The authors frame their work explicitly against the European Union’s Preparedness Union Strategy, launched in 2025, and the Common Security and Defence Policy, both of which reflect a continent grappling with the return of large-scale war to Europe. Global instability and ongoing conflict mean that civil defence, once viewed in many member states as a Cold War relic, has been thrust back onto the policy agenda. The nature of modern hybrid warfare, which blends conventional military force with cyberattacks, disinformation, sabotage and attacks on critical infrastructure, produces complex humanitarian emergencies that include mass casualty events. In such scenarios, civilian health systems become part of the defence apparatus, and nurses, who make up the single largest professional group within health services across the continent, become frontline actors in societal resilience whether or not they have been prepared for that role.

To map the existing evidence, the researchers conducted a scoping review following the PRISMA extension for scoping reviews, the internationally recognised reporting standard for this type of literature synthesis. The protocol was registered on the Open Science Framework on June 23, 2025, a step that increases transparency and guards against selective reporting. The team then carried out a comprehensive electronic search covering articles published between January 2000 and June 2025, a twenty-five-year window chosen to capture the full arc of contemporary security thinking in Europe. Five major bibliographic databases were searched: MEDLINE via PubMed, Embase via Ovid, CINAHL via EBSCO, PsycINFO and Web of Science. Supplementary searching of Google Scholar was also undertaken to catch grey literature and recently published work not yet indexed in the commercial databases.

The yield from this exhaustive search tells its own story. Of 836 articles identified in the initial sweep, only 16 survived screening and were included in the final review. That attrition rate, barely two percent of the retrieved literature, is the review’s most striking quantitative finding. It means that in twenty-five years of published health research, only a handful of studies have specifically examined the role of civilian nursing in civil defence within Europe against the backdrop of the current emerging threat landscape. For a workforce numbering in the millions across the European Union, and for a policy environment that now explicitly demands societal preparedness, the evidence base is essentially a void.

Where the literature does exist, it comes overwhelmingly from elsewhere. The review found that most of the relevant research emanated from the United States and the Middle East, regions where mass casualty events, military deployments and large-scale disasters have forced health systems to confront these questions directly. American nursing research has a long tradition of engagement with disaster preparedness, driven in part by events such as Hurricane Katrina and the post-September 11 emphasis on homeland security, while nursing scholarship from the Middle East reflects the brutal realities of protracted conflict. European nursing research, by contrast, has largely treated disaster and conflict response as someone else’s problem, a gap the authors argue can no longer be sustained given the security environment on the Union’s own borders.

Despite the scarcity of European evidence, the 16 included articles did converge on a central finding: nurses possess essential attributes for civil defence but are under-prepared for conflict scenarios. The attributes are not trivial. Nurses bring clinical skills in triage, trauma care and mass casualty management; they bring organisational experience in stretched, resource-constrained environments; and they bring a public-facing presence in virtually every community, hospital and primary care setting on the continent. In a hybrid war scenario, where attacks on civilian infrastructure may produce casualties distributed across time and geography, this distributed clinical capacity is precisely what a civil defence structure would need to mobilise. Yet the review indicates that this capacity remains latent, unrecognised in workforce planning and unsupported by dedicated training.

The authors characterise this as a significant policy-practice gap in disaster nurse workforce planning and training for Europe’s security landscape. On the policy side, the Preparedness Union Strategy and the Common Security and Defence Policy articulate ambitious goals for societal resilience, stockpiling, crisis coordination and civil-military cooperation. On the practice side, there is no pan-European framework for preparing nurses to operate within a civil defence structure, no standardised curriculum content on conflict-related mass casualty care, and no consensus on the ethical and legal dimensions of nursing practice under wartime conditions. The result is a strategy that implicitly depends on a workforce that has never been asked to think of itself in those terms.

The remedy the authors propose is correspondingly structural rather than rhetorical. They argue that within the framework of the Preparedness Union Strategy, the European Union must prioritise the development and implementation of policies that promote pan-EU standardised training integrating nurses into civil defence planning. The emphasis on standardisation matters: health workforce readiness that varies from member state to member state would leave predictable seams in any coordinated response, particularly for cross-border emergencies where mutual assistance mechanisms would be invoked. Because nurses constitute the largest professional group within health services, any comprehensive civil defence strategy intended to support European societal resilience and meet people’s health needs during conflict will succeed or fail largely on whether that group is included by design or left out by omission.

The review also carries implications that reach beyond workforce planning into education and ethics. If nursing curricula across Europe are to incorporate civil defence competencies, educators will need clarity on what those competencies are, and the near-absence of European primary research means that curriculum development would currently rest on evidence generated in very different health systems and conflict contexts. Questions of professional ethics also loom: the obligations of civilian nurses during armed conflict, the boundaries between humanitarian and military roles, and the protection of health workers under international humanitarian law are all areas where the review’s thin evidence base offers little European guidance. These are the kinds of questions that a follow-up research agenda, which the review implicitly calls for, would need to address.

What the study ultimately delivers is a diagnosis rather than a cure. By systematically demonstrating that only 16 relevant articles exist across five databases and twenty-five years, Wells and colleagues have quantified the gap between Europe’s stated preparedness ambitions and the professional group on whom those ambitions would most heavily depend. The review’s conclusion is measured but pointed: if the European Union wants a comprehensive civil defence strategy that genuinely supports societal resilience during conflict, it must treat nurses not as incidental participants but as central planners, and it must build the training, policy and research infrastructure to match. As the Preparedness Union Strategy moves from declaration to implementation, the review suggests that the most numerous members of Europe’s health workforce are also its most important unprepared reserve.

Subject of Research: The role of nurses in European civil defence and disaster preparedness under the EU Preparedness Union Strategy

Article Title: Complex disaster and conflict-related civil defence – nurses’ role in European civil defence within the context of emerging threats and the European union preparedness union strategy – a scoping review

Article References: Wells, J. S. G., Bennett, L., Crowley, J., Dobrowolska, B., Pajnkihar, M., Palese, A., Rajendran, A., Vrbnjak, D., Zdunek, K., & Scheibein, F. (2026). Complex disaster and conflict-related civil defence – nurses’ role in European civil defence within the context of emerging threats and the European union preparedness union strategy – a scoping review. BMC Nursing. https://doi.org/10.1186/s12912-026-05106-9

Image Credits: AI Generated

DOI: 10.1186/s12912-026-05106-9

Keywords: nurses, civil defence, European Union, hybrid warfare, disaster preparedness, scoping review, Preparedness Union Strategy, mass casualty events, nursing education, health policy, workforce planning, societal resilience