The role of science in resilience planning for military-civilian domains in the U.S. and NATO

ABSTRACT

In recent years, the NATO member nations have committed to a coordinated approach to strengthening resilience among the Allies, including the development of National Resilience Plans (NRPs). The Allies outlined the extent to which the robustness of their respective military capacities requires the designed resilience of systems that bridge civilian and military domains. This article outlines the role that resilience plays in supporting tactical and strategic measures of national security and defense within military and civilian domains. This exploration provides an outline of how resilience is currently applied in practice by the U.S. Department of Defense (DOD) and NATO. Building on this diversity of applications, various categorical forms of resilience drawn from the empirical science of resilience are positioned within NATO’s emerging frame for ‘layered’ resilience. This article reinforces the scientific debate that an optimal orientation to resilience leaves open the door for the transformative adaptation of function and identity when the single-equilibrium processes of resilience reach their limits. This article concludes with a normative perspective on how military and civilian resilience planning could support the development of NRPs that would amplify the Allies’ collective capacity to face shared security threats.

KEYWORDS:

• NATO
• resilience
• national security
• military
• civilian
• cybersecurity
• adaptation

Introduction

As the geopolitical landscape grows increasingly complex and interconnected across state boundaries, intense domestic disruptions from acute shocks and chronic stresses in any given state are capable of leading to global disruptions across a variety of meta-scales (Vina and Liu 2023). At the 2016 Warsaw Summit of the North Atlantic Treaty Organization (NATO), the member nations (or “Allies”) committed to adopting a more integrated and better-coordinated approach to strengthening resilience among NATO members (NATO 2016a). During that summit, the Allies released a Commitment to Enhance Resilience that defined baseline civil preparedness principles to ensure NATO military forces can always be adequately supported with civilian resources (Id.). At the Vilnius Summit in 2023, the Allies agreed to each develop a National Resilience Plan (NRP) to meet a new range of civil preparedness requirements (NATO 2023a). Here, the Allies outlined the extent to which the robustness of their respective military capacities requires the designed resilience of systems that bridge civilian and military domains.

This article outlines the complex relationship between military and civilian domains and the role that resilience plays and has played in supporting tactical and strategic measures of national security and defense. This exploration continues with an outline of how resilience is currently defined and applied in practice by the U.S. Department of Defense (DOD) and NATO. Building on this diversity of applications and perspectives, various categorical forms of resilience drawn from the empirical science of resilience are positioned within NATO Allied Command for Transformation’s (ACT) emerging frame for “layered” resilience that seeks to cut across military and civilian domains. This article argues that a more comprehensive utilization of resilience science requires greater epistemic precision of the various forms of resilience. These various forms of resilience offer a range of analytical models and measurements that may support a more robust quantification of performance within sectors and across military-civilian domains (Davidson et al. 2016; Wied, Oehmen, and Welo 2020).

This type of precision is important for not only guiding strategic design, but also stress testing and validating investments in resilience that address a wide range of shocks and stresses that may impair the defense capabilities of the Allies – associated with everything from climate change to artificial intelligence (AI) in cyberwarfare (Milburn 2023; Thornton and Miron 2020). With its often-invisible hand and ambiguous political goals, the meta-landscape of hybrid warfare extends from the psychological conditioning of labor and military force members to the systems of systems that drive the delivery of critical infrastructure services (Mumford and Carlucci 2023). Given the vast and deep uncertainty resident in global change and hybrid landscapes, this article reinforces the scientific debate that an optimal orientation to resilience leaves open the door for the transformative adaptation of function and identity when the single-equilibrium processes of resilience reach their limits (Folke et al. 2010; Yu et al. 2020). Finally, this article concludes with a normative perspective on how military and civilian resilience planning could be initiated in order to achieve a coordinated development of NRPs that would amplify allies’ collective capacity to face shared security threats.

National security, cross-domain deterrence and resilience

The primary purpose of the military in NATO nations is to protect and ensure the continuity and integrity of civilian institutions, assets, and infrastructure, as well as the welfare of the general population. Such civilian resources reciprocally provide support for and enable the operations and readiness of the military. The intensive convergent integration and interdependence of civilian and military domains raises several key issues concerning the state of democracy, the constitutional role of the civilian governance of the military (Brooks 2019) and the role of the state in an open society (Hartmann 2017; Popper 2020). Military and civilian domains have long been entwined with each other, manifesting in different ways – whether that is over the course of western social history (Karsten 2013) or contemporary economic discourses on the role of public military spending in the era of fair trade regulation and globalization (Meunier 2019).

The magnitude of this relationship has intensified as the world’s infrastructure and technology have grown in complexity, particularly as it relates to information technology (Lindsay 2020) and AI (Ams 2023). This technological integration has accelerated the proliferation of hybrid warfare (also referred to in literature as “hybrid threats”), which is a rapidly emerging vector by which interstate hostility is conducted (Linkov et al. 2019). Hybrid threats embody a complex blend of conventional and unconventional tactics, orchestrated by state or non-state actors to exploit vulnerabilities across a wide spectrum of domains, including military, economic, social, and cyber (Hartmann 2017). These multifaceted threats are characterized by their covert nature, strategic ambiguity, and the deliberate blurring of lines between peace and conflict, which aim to undermine societal cohesion, erode trust in institutions and destabilize targeted nations without triggering a conventional military response. For NATO, addressing hybrid threats is paramount, as they directly challenge the alliance’s mission of collective defense and security through non-conventional means, particularly where adversaries can leverage vulnerabilities in NATO member critical infrastructure while maintaining plausible deniability (Jacuch 2020). The sophisticated nature of these threats benefits from a resilience-oriented approach, emphasizing the need for agile, adaptive strategies that can respond to the dynamic and often indistinct contours of hybrid warfare.

Military-civilian cyberspace and cyber-physical integration has created a new landscape for both low-scale conflict and the potential for mass destruction within civilian systems and economies that serve as a multi-lateral deterrent to classical forms of warfare (Gartzke and Lindsay 2019). Indeed, cross-domain deterrence (CDD) has arisen as an important dimension of strategic motivation and capability. “When an opponent has no incentive to initiate or escalate conflict at any given intervention or escalation threshold in any given domain of warfare – both vertically and horizontally within that domain and laterally into one or more additional domains of warfare – successful cross-domain deterrence can be said to be in effect” (Mallory 2018, 1).

There are two dimensions to CDD relevant in the context of resilience. First, low-scale indirect cyber warfare presents an alternative to classical forms of military aggression wherein the geopolitical stakes may be lower for forms of aggression that do not present visceral forms of destruction and loss of human life. They may simply be deniable and hence avoid clear punitive consequences. For instance, the People’s Liberation Army of China deems “financial warfare” as something that can be just as destructive through “man-made stock market crashes, attacks on financial instruments, and cyber-attacks on the financial systems” (Reinike 2020, 8). In the context of the global marketplace, attacks associated with financial warfare may be plausibly deniable, as any number of unregulated market-based and/or criminal actors may be at work. This level of anonymity and plausible deniability makes hybrid warfare attractive, as the consequences are lower. It is difficult for the target nation to attribute the attack to a specific actor or nation. To this end, some scholars have sought to frame proactive “economic” resilience measures in the financial system that seek to detect and manage responses to malfeasance in everything from currencies to portfolios (Constantinescu 2023; Smalenberger 2015).

Second, by extension, one could argue that the greater the robustness in resilience within civilian infrastructure and populations, the less valuable the target. In such cases, the aggressor is limited in their offensive capacity to classical forms of military assault within a military domain which may be geopolitically and technologically limited. In this sense, resilience itself may be a form of CDD. As Sweijs, et al. note, “[r]esilience is directed at dissuading hostile measures by presenting the adversary with the futility of his attacks through recovery” (Sweijs et al. 2021, 16–17). In this light, Hartmann notes that resilience is “a constant process of adaptation [that is] potentially able to undermine the effectiveness of hybrid warfare, and, thus, deter opponents” (Hartmann 2017, 8). Some commentators among the Allies have viewed resilience as key element of deterrence (Roepke and Thankey 2019). They have argued that countries with greater measures of resilience, usually characterized by comprehensive preparedness planning involving government, public, and private sectors, possess fewer vulnerabilities susceptible to exploitation or targeting by adversaries (Id.). Thus, resilience becomes a critical component of CDD through denial, thereby aiming to dissuade adversaries from attacking by demonstrating that such actions would fail to accomplish their objectives while at the same time risking the consequences of the identification of proxy actors and methods.

Resilience performance through military and civilian integration may manifest, not just as a form of CDD, but also as a very practical prerequisite for military mobilization and tactical execution. NATO’s use of the concept of “enablement” refers to the overarching capacity to mobilize extensive military forces and allocate resources across the NATO area of responsibility seamlessly, encompassing periods of peace, crisis, and conflict (Lindley-French 2021). This capability is deemed essential for establishing a credible deterrence posture. In times of direct military conflict, militaries utilize much of the same infrastructure that civilians rely on. The relationship becomes more complicated when one considers the prospects of transnational defense and mobilization wherein NATO forces operate across multiple physical and cyber infrastructural systems across state-borders (Frizzelle, Garey, and Kulalic 2022). Hence the challenge is not just cross-jurisdictional interoperability standards, but also the management of vulnerabilities such as foreign direct investment and control of critical infrastructure (Id.).

Military and civilian integration exists not just between the military and civilian infrastructure, but such integration also extends to the general civilian population. Some commentators have noted that “whole-of-government and “whole-of-society” resilience strategies that have framed recent integration efforts discussed herein are “top-down” and not sufficiently invested in bottom-up civilian institutional capacities for threat-perception, detection and mitigation (Manwaring and Holloway 2023; Kott et al. 2024). As such, civilian institutions and assets (e.g. infrastructure) should be distinguished from the broad range of capacities at a population-level. For instance, some have argued that Ukraine did not fall during the Russian invasion due in large part to civilian resilience (Goodwin et al. 2023). Kudlenko attributes Ukraine’s resilience to numerous factors including a history of decentralization and self-organization that allowed for a continuity of institutions and systems when national and federal systems were impaired during physical and cyber assaults (Kudlenko 2023).

To this end, cultural, historical and legal qualities of the general population are understood to be an important element of military and civilian integration and resilience. In recent years, NATO has focused on citizen-level resilience that is centered on societal processes (Christie and Berzina 2022; NATO 2022a). The COVID-19 pandemic and potential future crises that deeply impair the mobilization of the general population emphasize the significance of civil societies in national preparedness and responses. This includes roles in facilitating effective public communications and ensuring access to transparent, timely, and accurate information to combat disinformation (Reding and Wells 2022).

Defining resilience from DOD to NATO

The United Nations (UN) has 129 English-language entries for resilience in its official terminology database (UN 2023). The U.S. government has at least eight (8) different formal definitions of resilience (DOD 2019). Some of these definitions across the U.S. government are defined in congressional legislation that relate to particular policy goals. For instance, the U.S. Department of State (DOS) utilizes a statutorily definition that defines resilience, in the context of foreign food aid, as “the ability of people, households, communities, countries, and agriculture and food systems to mitigate, adapt to, and recover from shocks and stresses to food security, including global food catastrophes, in a manner that reduces chronic vulnerability and facilitates inclusive growth”(22 U.S.C. § 9303(9)).

On the other hand, the U.S. Department of Defense (DOD) does not have a single overarching definition of resilience despite prior proposals for developing such a definition (Herrera 2021). Nonetheless, within DOD, resilience planning appears in three core focus areas, including force readiness, cyber security, and military installations. Often these focus areas are shaped by congressional legislation and appropriations. For instance, “military installation resilience” is defined as:

[t]he capability of a military installation to avoid, prepare for, minimize the effect of, adapt to, and recover from extreme weather events, or from anticipated or unanticipated changes in environmental conditions, that do, or have the potential to, adversely affect the military installation or essential transportation, logistical, or other necessary resources outside of the military installation that are necessary in order to maintain, improve, or rapidly reestablish installation mission assurance and mission-essential functions (10 U.S.C § 101(e) (8)).

Engineering resilience concepts for military installations have also been extended to the Production-based Resilience Program (PRP) and the Industrial Base Resilience (IBR) policies for weapons, advanced technology and other critical supply chains within the defense industrial base (DOD 2024; Nicastro 2023). On a tactical level utilizing the aforementioned statutory authority for military installation resilience, the DOD created the Readiness and Environmental Protection Integration Program (REPI) as a means to understand how engineering resilience and ecological resilience efforts may shape force readiness capacities and capabilities through an integration of relevant military and non-military public, private and civic stakeholders (REPI 2023). In the closely related context of climate and global change, the DOD defines resilience as “[t]he ability to anticipate, prepare for, and adapt to changing conditions and withstand, respond to, and recover rapidly from disruptions” (DOD 2018). Resilience is also thematically applied at a strategic level, as highlighted by the creation of the office of the Deputy Assistant Secretary for Defense for Arctic and Global Resilience. This office is charged with ensuring the DOD’s competitive advantage as it relates to sociotechnical and political changes relating to the energy transition, among other aspects of national security relating to environmental change (DOD 2023b).

Different forms of resilience are broadly utilized in everything from climate change planning to force readiness. Across the services of the U.S. military, there is an application of the concepts of resilience originating from the fields of psychology and psychiatry to support everything from mental and physical health to force readiness of personnel (McInerney, Waldrep, and Benight 2022). For instance, the U.S. Army, within the Office of the Deputy Chief of Staff, has a Directorate of Prevention, Resilience and Readiness that defines resilience as “the ability to persevere, adapt, [and] grow in dynamic or stressful environments” (U.S. Army 2023). In this case, the stress is on the individual. More broadly, the Office of Force Resiliency (OFR) within the Undersecretary of Defense for Personnel and Readiness focuses on a wider variety of issues including, “diversity management and equal opportunity, personnel risk reduction, suicide prevention, [and] sexual assault prevention and response” (OFR 2023).

Beyond force readiness and climate change applications driving resilience planning at the DOD, cyber resilience is increasingly a focus of policy and planning at DOD (DOD 2023a; Linkov and Kott 2019). Early work in cyber resilience defined resilience as an “ability to provide acceptable operations despite disruption: natural or man-made, inadvertent or deliberate” (DOD 2013). Yet, performance and operations standards for resilience at the time, a decade ago, did not exist, with the Defense Science Board warning that “[p]oorly defined and improperly used metrics may prove as harmful as no metrics at all (DOD 2013, 15). MITRE would later go on to develop resilience metrics that focused on performance before and after a detected or detectable event with a focus on the “time between disruption, detection, response and recovery” (Bodeau et al. 2018).

DOD would later build on the work of the National Institute of Standards and Technology (NIST) at the U.S. Department of Commerce who has led work on cyber security across the U.S. government. NIST has two different definitions for “cyber resiliency,” including “[t]he ability to anticipate, withstand, recover from, and adapt to adverse conditions, stresses, attacks, or compromises on systems that use or are enabled by cyber resources” (NIST 2020). The second definition builds on the first definition by noting that “[c]yber resiliency is intended to enable mission or business objectives that depend on cyber resources to be achieved in a contested cyber environment” (NIST 2021). Cyber resilience activities for both internal networks and external contractors has been extended in defensive posture at units such as the Department of Defense Cyber Crime Center and more broadly at DOD’s Under Secretary of Defense for Research and Engineering. At the current stage of development, cyber security, with its risk management orientation, and “operational resilience” were programmatically segregated, with operational resilience being defined as “the ability of systems to resist, absorb, and recover from or adapt to an adverse occurrence during operation that may cause harm, destruction, or loss of ability to perform mission-related functions” (DoDI 8500.001(DOD 2019)). In this context, cyber resilience has been largely relegated to a principled goal or objective and less of a quantification of designed processes. This finding is reinforced by the National Academies of Sciences, Engineering and Medicine’s (NASEM) publications published by the Forum on Cyber Resilience, which do not define resilience and offer little to no direct methodological advancement in the forum’s publications (NASEM 2023).

Across many aspects of the U.S. government, resilience is largely relegated to a qualifiable objective, yet it is viewed by DOD as a critical element of its defense strategy. The 2022 National Defense Strategy (NDS) defines resilience as “the ability to withstand, fight through, and recover quickly from disruption” (DOD 2022, 8). The NDS explicitly reinforces the proposition that resilience planning is an effective mechanism for CDD by noting in a section entitled “Deterrence by Resilience” that “the Department will reduce adversary incentives for early attack by fielding diverse, resilient, and redundant [assets]. We will bolster our ability to fight through disruption by improving defensive capabilities and increasing options for reconstitution. We will assist Allies and partners in doing the same” (DOD 2024, 8). Indeed, building on domestic interagency resilience practices, the Defense Security Cooperation Agency within DOD has an active program in training partner nations (DSCA 2021). Indeed, the NDS specifically cites the intent to support NATO Allies through “promoting resilience, including against hybrid and cyber actions” (DOD 2022, 15).

While the U.S. government and DOD have approached resilience from a variety of bottom-up thematic areas focused on strategic objectives, NATO has approached resilience planning from a largely top-down central planning orientation that starts with a meta-system perspective. NATO formally defines resilience in two contexts. In the context of information technology, which is critical for hybrid warfare applications, resilience is defined as “[t]he ability of a functional unit to continue to perform a required function in the presence of faults or errors” (NATO 2005). In the general terminology of NATO, resilience is officially defined as “[t]he ability of an entity to continue to perform specified functions during and after an attack or an incident” (NATO 2022b). Here, resilience is oriented towards episodes, shocks and known or potentially detectable phenomena.

Following the 2016 Warsaw summit, NATO shifted its focus further towards a broader orientation of resilience by positioning resilience within the related-concept of non-military preparedness (NATO 2016a). As a designed capability, resilience is rooted in Article 3 of the North Atlantic Treaty, which states, “[i]n order to more effectively achieve the objectives of this Treaty, the Parties, separately and jointly, by means of continuous and effective self-help and mutual aid, will maintain and develop their individual and collective capacity to resist armed attack” (NATO 1949). For NATO, civil preparedness has been the focus of this historically implied and current requirement for resilience planning, also reiterated in Vilnius in 2023 as “resilience through civil preparedness” (NATO 2016b, 2023a).

However, in recent decades, there has been a corresponding decline in investments in civil preparedness (H. Larsen 2022) and an increased reliance on private sector actors to provide critical services and infrastructure (Newlove-Eriksson, Giacomello, and Eriksson 2018; Radvanovsky and McDougall 2018). In the Cold War era, essential infrastructure like railways, ports, airfields, grids, and airspace were predominantly under state control in Europe, which facilitated their transfer to NATO authority in times of crisis or conflict. By contrast, approximately “90% of NATO’s supplies and logistics are moved [today] by private companies and 75% of the host nation support for NATO forces forward deployed on the territory of the eastern Allies comes from private sector contracts” (Shea 2016). Against this institutional backdrop, there have been emerging threats such as hybrid warfare, climate change (Rico 2022), the COVID-19 pandemic (Missiroli and Rühle 2021) and the emergence of AI capabilities (Porkoláb 2020) that have added additional prolonged stress that undermine conventional shock-oriented recovery and response mechanisms of civil preparedness.

It is at this juncture that resilience is thought to fill a strategic void. As some scholars have noted, there is arguably a “need for much broader political, economic, technological and societal resilience in the face of hostile acts below the threshold of war” (Hall and Sandeman 2022, 5). Indeed, it is the interaction between chronic multivalent stresses that exist below the threshold of war and actual direct military confrontation, capabilities and deterrence that is at the heart of a resilience strategy. In this sense, resilience is both the “first and last line of defense” (Hall and Sandeman 2022, 1). It is the first line of defense insofar as it serves as a CDD and it is the last line of defense in the face of shocks – and shocks whose systemic and asset sensitivity is amplified by regular and prolonged multivalent stresses.

How science can support ‘layered resilience’

While the applications of resilience policies at national and international levels are gaining prominence, the formulation of policies and processes across sectors has not fully availed itself of the science of resilience. The science of resilience suggests that there is no one single or universal definition or conceptual framing of resilience. Rather there are a variety of major categories that have emerged over time in core disciplinary areas of science and each of these categorical forms of resilience possesses its own conceptual and analytical autonomy, empirical application and external validity (Davidson et al. 2016; Joseph 2018; Mentges et al. 2023). Key categorical forms of resilience are applied in physical, informational, cognitive, and social domains (Wells et al. 2022).

Across these domains, many different forms of resilience are programmatically applied across the U.S. government policy, including engineering resilience, cyber resilience, operational resilience, ecological resilience and community resilience (Kang et al. 2023; Keenan 2018a, 2018b). Even within civil engineering and critical infrastructure systems design and management, these different types of resilience serve different functions, metrics, and assessments (Field et al. 2022). This conceptual plurality within material systems of the built environment and across economic sectors is also widely observed in European policy (Capraru 2022; Baravikova, Coppola, and Terenzi 2021).

Appendix Table A1 provides a non-exhaustive overview of key categorical forms of resilience found in American and European policies and programs. This table provides a heuristic reference to each categories’ properties, attributes and performance criteria. Some forms of resilience, such as engineering resilience and disaster resilience, are primarily concerned with an elastic and reversionary process that reverts to the pre-perturbation state (Wied, Oehmen, and Welo 2020). This is often referenced as a single equilibrium process (Zampieri 2021). These forms of resilience are focused on designed processes within the context of engineered systems and systems-of-systems (SoSs) wherein fixed levels of performance have been optimized to a robust range for purposes of reliability, safety, efficiency and other limiting factors (Martello et al. 2021; Park et al. 2013). Conversely, within the context of multi-equilibrium processes, other forms of engineering resilience may provide an underlying capacity for adaptation wherein the designed resilience performance may result in a superior level of performance across its lifecycle in a post-perturbation state (Ungar 2021; Woods 2015). In either case, scholars have noted the value of utilizing different forms of resilience across systems within SOSs as a means to decomposing and managing case-specific complexities, as Uday and Marais note:

Although there are advantages to using a single calculated value to define resilience, it is also important to recognize the potential issues associated with doing so [Haimes 2009]. In particular, an overall metric provides little, if any, information regarding specific areas within the SoS that need attention. Also, in the context of SoSs, the uncertainties associated with network operations, evolution, and management are quite large and hence one metric may not be able to capture all the unknowns. To address these concerns, some studies focus on capturing or disentangling the various dimensions of resilience. (Uday and Marais 2015, 502)

In a different context of complex adaptive systems, ecological resilience is also a multi-equilibrium phenomena that is concerned with the degree of external impact that an ecological unit may endure while still maintaining its key identify and performance measures in what might otherwise be shifting responsive structures (Dakos and Kéfi 2022). Other forms of resilience, such as community resilience, are focused on people and social behavior and may be explicitly multi-equilibrium phenomena due to the social learning and the modification of behavior that leads to forms of adaptation (Koliou et al. 2020). Social dimensions of resilience have also found specialized forms across scales – from individuals (i.e. psychological resilience)(Denckla et al. 2020), organizations (i.e. organizational resilience, operational resilience) (Essuman, Boso, and Annan 2020; S. E. Galaitsi et al. 2023), and institutions (i.e. economic resilience, financial system resilience) (Hynes et al. 2022; Keenan et al. 2021).

Social aspects of resilience – often referenced as “community resilience” – specifically addresses the capacity of communities and societies to effectively confront, adapt to, and recover from external perturbations (Koliou et al. 2020), including the complex impacts of hybrid and conventional warfare (Zekulić, Godwin, and Cole 2017). This form of resilience is pivotal in safeguarding societal coherence, morale, and the continuity of social functions amidst the psychological, informational, and physical disruptions posed by such conflicts (Hadji-Janev 2018; Lee et al. 2022). The essence of community resilience in this milieu involves the strategic cultivation of societal attributes such as informed awareness, communal solidarity, and adaptive governance structures. These elements are crucial for mitigating the divisive and destabilizing tactics employed in hybrid warfare, which often targets the social fabric through disinformation campaigns, cyber-attacks, and other forms of indirect aggression (Apostol, Cristache, and Năstase 2022).

Furthermore, the resilience of social systems against conventional warfare demands a comprehensive approach that spans the psychological preparedness of civilians, the maintenance of critical societal functions, and the preservation of cultural heritage (Nikolov 2018). Mechanisms for fostering social resilience include community-based education and training programs that enhance disaster readiness, the development of infrastructure, particularly communications infrastructure, capable of withstanding physical and cyber-attacks, and policies that support economic and social recovery post-conflict. Such strategies not only aim to preserve the immediate welfare and security of the population but they also ensure the long-term viability and cohesion of the social structure, thereby reinforcing the overall resilience performance of the state against the multifarious challenges of modern warfare (Wigell, Mikkola, and Juntunen 2021).

Wherein some forms of resilience (i.e. engineering resilience, disaster resilience) are explicitly designed as endogenous processes that may be directly indicated, other forms of resilience may be defined by innate characteristics (i.e. psychological resilience) or normative outcomes (i.e. community resilience). Because some forms of resilience may be defined by objectives (e.g. engineering) and others may be defined by characteristics (e.g. ecological resilience, psychological resilience), it “becomes imperative to understand and establish interlinkages between the objectives and characteristics,” as there may be a misalignment and/or direct conflict of objectives across scales (Kolte et al. 2023, 11). For this reason, it is often necessary to draw analytical distinction between the various forms of resilience across scales in order to “disentangle” objectives and characteristics and processes and outcomes.

This diverse application of different forms of resilience across sectors has not been widely internalized within national security policies, which has tended to utilize a singular form of engineering resilience in general and non-specific terms. Unfortunately, early applications of resilience in American national security policy development lacked scientific specificity and therefore were viewed by some scholars as “an exercise in ‘occupying’ them with ideologically loaded meanings, which can be interpreted as the actualisation of … ‘political keywords’”(Selchow 2017, 36). In Europe, the incorporation of resilience into national security raised a more fundamental critique that “resilience [is] a way to ‘act on the cheap’ removing responsibility from the international community, as local actors become the main protagonists – and in case of failure, the main culprit – of conflict management, also potentially leading to an indirect legitimization of dysfunctional local practices for conflict and security management” (Baldaro and Costantini 2021, 309).

Yet, other scholars have noted that resilience in the context of security policy represents a fundamental shift in a theory of governance. Chandler notes, “[t]he area where resilience-thinking has gone furthest is in the rejection of modernist or liberal approaches to governance, based upon linear or deterministic knowledge assumptions of causality. For liberal universalist approaches, policymaking is constructed in ‘top-down’ ways, determined by the ‘known knowns’ of established knowledge and generalisable assumptions of cause and effect” (Chandler 2014, 62). In rejecting a linear and deterministic orientation to external shocks and stresses, an extension of this position would suggest that resilience policy is or should be – at its best – grounded in a bottom-up orientation that acknowledges unknowns and deep uncertainty in a world that is shaped by increasing interdependencies and rapid rates of global change manifested across scales and sectors.

In 2021, the Allies endorsed the NATO Warfighting Capstone Concept that introduced “layered resilience” as one of five development imperatives necessary for current and future security challenges (NATO 2022c, 2023c). In broad terms, layered resilience relies on different sectors across military-civilian domains to each demonstrate their own resilience performance measures and thus enable NATO to sustain, if necessary, long and protracted campaigns (van Mill 2023). NATO’s layered resilience model largely imagines the Alliance, its constituent militaries, and the civilian sectors of those countries as components of multiple layers of interaction and dependencies that define security capacities and resilience processes. Table 1 outlines the various frames and definitions for each of the respective layers within this conceptualization of layered resilience.

Table 1. Resilience definitions within NATO’s layered resilience framework.

Concept	Definition	Closest Categorical Form of Resilience	Includes Adaptation	Citation
Alliance Resilience (AR)	“[T]he combined capacity of Allied societies’ ability to resist and recover from major shocks from both manmade threats (i.e. hybrid or armed attack) or natural hazards (i.e. natural disaster or pandemic), and combines both civil preparedness and military capacity.”	Engineering Resilience, Disaster Resilience	No	NATO (2023d)
	“[D]escribed as the individual and collective capacity for Allies to resist and recover from military, civilian, economic and commercial shocks, absorb damage and resume function as quickly and efficiently as possible.”	Engineering Resilience	No	NATO (2023b)
Military Resilience (MR)	“[D]escribes a resilient NATO Military Instrument of Power (MIoP)3 that has three core functions based on the continuity of Alliance forces’ ability to: deter, defend and support the civil environment. To meet these functions, the Resilient MIoP must coordinate with relevant non-NATO actors and be able to continuously anticipate, adapt and prepare to counter threats and hazards and, withstand, respond and recover rapidly from strategic shocks.”	Engineering Resilience	Yes	NATO (2023d)
	“[I]includes the forces being ready for employment with the capabilities and redundancy the military instrument requires to ensure its ability to absorb shocks, provide early resistance and conduct counter offensive operations.”	Engineering Resilience	No	NATO (2022b)
Military-Civilian Resilience (MCR)	”[I]includes those plans, processes and connections that must be in place to ensure civilian support and infrastructure, transport and logistic supplies are a strength and not a vulnerability.”	Engineering Resilience	No	NATO (2022b)
Civilian Resilience (CR)	“Based on Civil Preparedness, which has three core functions: Continuity of government, continuity of essential services to the population, and continuity of civil support to military operations.”	Engineering Resilience	No	NATO (2023b)
	”[T]he civil ability to deny competitors the ability to target civil vulnerabilities and distract/overstretch the military instrument. It also includes those forces and capabilities that the military instrument will be expected to deploy in support of civilian society in the case of human-made disasters, as well as shielding the society from adversaries’ malign activities.”	EngineeringResilience, Disaster Resilience, Community Resilience	No	NATO (2022b)

NATO’s framing of layered resilience with Alliance Resilience (AR), Military Resilience (MR), Military-Civilian Resilience (MCR) and Civilian Resilience (CR) has a very close conceptual orientation to applications of engineering resilience previously utilized in transatlantic security policies. In this limited context, Table 2 provides an alternative orientation to layered resilience that highlights various scientific applications across select categorical forms of resilience. These examples largely represent ongoing activities across units of military and civilian governance that may be overlooked for their interactive and cross-scale relationships. For instance, national climate adaptation planning within the context of ecological resilience and AR may significantly shape and support MR and MCR processes that are managing and adapting to environmental and climate risk in physical facilities, installations, and industrial networks. In an entirely different realm of risk and uncertainty, applications drawn from psychological resilience may support everything from the countering of malicious misinformation within the AR and CR domains to force readiness and mobilization within MR and MCR domains. Similar benefits may arise from investments in community resilience in terms of force readiness, labor training, and civilian transition management from the MR, MRCR and CR domains and may even offer the opportunity for reductions in social vulnerability within the AR domain.

Table 2. Example applications of scientific categories of resilience across nato’s layered resilience model.

			Engineering Resilience	Disaster Resilience	Ecological Resilience	Community Resilience	Psychological Resilience
Alliance Resilience (AR)			Continuity of Government; Institutional Redundancy and Operations Continuity for Strategic and Logistics Command and Political Communications (Joseph 2018; Hodicky et al. 2020)	Cross-Jurisdictional Mutual Aid Agreements and Processes (DSCA 2021)	Cross-Border Environmental Regulation and Measurement; National Climate Adaptation Planning (Pennington 2020)	Monitoring Emergent Public Health Events, Social Welfare and Vulnerability, and Invest in Shared Public Health and Social Support Resources (Chandra et al. 2010; Cutter and Derakhshan 2019)	Monitoring and Countering Malicious Misinformation Campaigns in Health, Crime, Foreign Relations, Elections and Public Trust (Bonnevie, Sittig, and Smyser 2021; Maronkova 2021)
Military Resilience (MR)			Installation and Asset Preparedness and Risk Mitigation (DOD 2018; Herrera 2021)	Event Contingency and Scenario Planning and Training (DSCA 2021)	Measure, Monitor, Mitigate and Adapt Impacts to Ecosystem Services Support Operations (DOD, 2018; REPI 2023)	Manage Force Readiness (OFR 2023; U.S. Army 2023)	Manage Force Readiness; Monitor Mental Health and Radicalization (McInerney, Waldrep, and Benight 2022; OFR 2023; U.S. Army 2023)
Military-Civilian Resilience (MCR)			Classify and Protect Critical Infrastructure, Production Base, and Cyber Networks; Audit and Test Critical Networks; Cross-Domain Intelligence Gathering and Mitigation; External Utilization of Contractors with Flexible Resilience Capabilities (Cusumano 2018; NIST 2020; Nicastro 2023; DOD, U 2023a; DOD 2020)	Joint Pre-and Post-Disaster Mobilization; Resource Reserve Management (Puckett 2021)	Deployment of Sustainability, Biodiversity, Climate Mitigation and Climate Adaptation Cross-Sector Protocols and Disclosure Reporting; Shared Data Ecosystem for Water and Air Quality; Environmental Security and Peacebuilding (Johnson, Ide, and Cruz 2023; Schilling et al. 2017; Vogler 2023)	Identify, Train, Develop and Protect Key Personnel at Various Stages of Deployment and Mobilization; Support Adaptability Between Military and Civilian Jobs (Oprins, Bosch, and Venrooij 2018; Stette, Porath, and Muehlich 2023)	Intelligence and Counter Measures in Cognitive Warfare; Identify, Develop and Support Key Personnel Through Mobilization, Demobilization and Remobilization; Identify and Monitor At-Risk Key Personnel (Claverie and du Cluzel 2022; MacLeish 2020)
Civilian Resilience (CR)			Cyber Network Security Performance Standards and Critical Infrastructure Systems; Critical Infrastructure Levels of Service Standards (Liu and Song 2020; NIST 2021)	Business Continuity and Organizational Resilience of Dependent Producers (S. E. Galaitsi et al. 2023)	Environmental Impact Management for Industrial Symbiosis (Fraccascia, Giannoccaro, and Albino 2017)	Invest in Public Health Institutions and Surveillance; Occupational Health and Exposure; Job Training and Technical Education; Physical Fitness (Patel et al. 2017; Sharifi 2016)	Invest in Mental Health Support; Monitor Malicious Misinformation Campaigns (Manwaring and Holloway 2023)

Table 2 outlines a variety of potential linkages across domains within the various categorical forms of resilience. Some of these forms of resilience may allow for and support an adaptive capacity for transformation, not necessarily available or inherent in linear top-down policy making as shown in Table A1. While some forms of resilience may reinforce reliability and safety dimensions of critical infrastructure systems in a single equilibrium context, other forms acknowledge the potential value and capacity for transformation (i.e. adaptation) when thresholds for single equilibrium recovery are either undesirable, infeasible or otherwise not possible. For instance, adaptation plays a central role in ecological resilience – vertically – across domains from AR to CR, as multiple domains and sectors will need to prepare for and respond to climate change impacts. There are also horizontal connections within a single domain. For example, ongoing advancements at DOD in climate adaptation planning within installations, facilities and force readiness is a prime example of the interaction between engineering resilience (i.e. often but not always single equilibrium) and ecological resilience (i.e. multi-equilibrium) within the MR domain wherein environmental conditions are expected to far exceed current steady state operational parameters (Garfin et al. 2021).

Carrying forward this example, these horizontal connections between different forms of resilience within the MR domain share a convergent scenario where installations must be secured (engineering resilience); people must be secured and protected (disaster resilience); assets must adapt (ecological resilience); forces must take on new operating conditions and health precautions (community resilience); and, force personnel must be prepared to improvise in the face of the stress of change and disasters (psychological resilience). Yet, this example represents a singular and unilateral risk vector that may impact military capabilities. When hostile acts compound simultaneously with natural disasters and climate impacts, for example, then the value of resilience is the capacity to execute planned recovery and “to improvise” beyond the limits of resilience in order to change structures to transform to a new operational state (Pursiainen and Kytömaa 2023, 10). For instance, redundant communications hardware and infrastructure designed for post-disaster coordination may serve as a critical lifeline during a cyberattack, which may also, by extension, increase the cyber resilience of dual-use command, control and communications supporting military capabilities (Afina, Inverarity, and Unal 2020).

This is not a far-out hypothetical scenario, as cyber-attacks have been observed to increase in number following natural disasters (Lallie et al. 2021). Years before the Russian military invasion of Ukraine, hackers, widely believed to be associated with Russian state-sponsored groups, launched a sophisticated attack in December 2015 that resulted in power outages for several hours in parts of western Ukraine. The attackers used malware to gain access to the control systems of energy distribution companies, manipulating and disrupting the operation of critical infrastructure and highlighting the vulnerabilities inherent in critical infrastructure sectors (Condliffe 2016).

Resilience may support transformative adaptation

Transformative adaptation may take over when the limits of resilience have been reached. Resilience narrowly viewed through traditional risk management strategies often focuses on specific, known threats, creating targeted solutions that may become inadequate or obsolete as new challenges emerge (Linkov, Trump, and Fox-Lent 2017). Risk is inherently uncertain. It is often impossible to predict the threats that will emerge, their magnitude, or the likelihood or existence of a specific threat scenario (Hynes et al. 2022). Planners attempting to mitigate all known risks will face prohibitive costs due to the sheer number of possible disruptions – most of which will never emerge as actual disruptions (S. Galaitsi et al. 2022). In contrast, resilience is often threat-agnostic because it processes system performance regardless of the nature or origin of the disruption (Pescaroli et al. 2023). A continuing challenge of investing in resilience is the fact that, in many cases outside of designed single equilibrium forms of engineering resilience, it is not easy to measure. Measurement is often clouded by the uncertainty of the timing of an event and the extent to which resilience performance may be self-executing. Therefore, probabilistic expected values and net present value optimizations originating from risk management processes are less useful for quantifying resource trade-offs supporting resilience investments than other forms of robust decision-making. This measurement challenge may result in an underinvestment in resilience. As a backstop, investments in forms of resilience that support the adaptive capacity of a system are the preferred pathway when total and complete system failure increases the likelihood of military defeat.

One challenge with existing frames of NATO ACT’s preliminary resilience model is that it often represents stability features as a baseline for resilience performance, which is consistent with early applications of single equilibrium forms of engineering resilience utilized in national security policies. The various forms of resilience shown in Table A1 highlight that adaptation largely falls outside of the conceptualization of NATO ACT’s layered resilience framework. In this context, there is little defined room for multi-equilibrium outcomes – or multiple stable states – that may address the inevitability or uncertainty of the dynamics and thresholds of systems and SOSs. The pursuit of resilience in military and deterrence policy is arguably most effective when it prioritizes both the capacity to recover and the capacity to adapt (formerly, adaptive capacity) within a designed multi-equilibrium resilience context.

Adaptation is critical, particularly in the context of when frontline defense and resistance to acute shocks fails. Under one common scenario, a defense may simply fail because the acute shock or attack was either unknown or undetectable. For instance, in the NATO description of MR, the deterrence operation to adapt occurs in a linear condition only under circumstances of known and anticipated risks. By the same token, defense may manifest to known or unknown (but detectable) phenomena, but the ultimate outcome under this emergent layered resilience framework is presumed to be the recovery to the pre-event baseline. It does not conceptualize a potentially superior alternative state achievable through transformative adaptation defined by new structures and processes. Both known and, particularly, unknown phenomena may cross thresholds from which pre-event baseline conditions are either impossible or undesirable. Resilience is only useful if military commanders and NATO decision makers can understand and operate from the knowledge that systems can and will eventually fail, and that resilience is largely the capability or pathway to flexibly recover and/or adaptively execute new structures that support core functions and performance measures in the eventual case that such systems fail.

Equally, effective adaptation to conventional and hybrid threats requires an understanding and integration of societal systems into NATO doctrine, preparedness, and best practices. Particularly for hybrid threats, it is incumbent upon policymakers to ensure that societal systems and collective human intelligence is able to adapt to the shifting nature of hybrid threats, particularly in the emerging era of generative artificial intelligence (Terziyan et al. 2021). This necessitates a resilience framework that not only anticipates and withstands attacks but also evolves in response to unknown or anticipated threats, ensuring societal structures can dynamically adjust and maintain critical functions. Emphasizing societal aspects of resilience policy within NATO’s strategy involves reinforcing public awareness (Lillemäe, Talves, and Wagner 2023), enhancing digital literacy, and fostering a culture of adaptability and innovation (J. A. Larsen 2023). By doing so, NATO can create a more robust defense ecosystem, one that leverages the collective resilience of its member states to navigate and overcome the multifaceted challenges posed by both known and unforeseen threats.

Figure 1 highlights the extent to which a narrow focus on single equilibrium forms of engineering resilience in national security policies may contribute to maladaptation. As the intensity of single and multi-vector hostile acts increases, so too may the corresponding measure of consequences. This is because the resilience performance is reliant on a set of fixed design parameters and resources that may not scale with the increased intensity (or novelty) of hostile action or the convergence of multiple acute extreme events. At some point, the resilience threshold may be reached and the traditional “V” curve of resilience – where the post-perturbation state equals the pre-perturbation state – is degraded to the extent to that the post-perturbation performance is inferior to the level of pre-perturbation. To this end, an inferior performance of resilience at this stage may also be defined by a longer execution time and at a greater cost. Such an outcome defined by the stress and strain on the elastic performance of resilience would suggest that there is a greater capacity for maladaptation as the intensity (or novelty) of hostile acts increases. This may simply be because any attempt at transformation at the edge of a resilience threshold may be based on the same limited assumptions and resources of pre-perturbation designed resilience. As such, processes and policies that are “too rigid pose any obstacle to improvisation”(Pursiainen and Kytömaa 2023, 10). Indeed, if the resilience function collapses entirely without any subsequent adaptation, then total failure or worse (maladaptation) may be the result.

Figure 1. Maladaptive implications for utilizing single equilibrium forms of engineering resilience.

By contrast, Figure 2 highlights the value of the utilization of forms of resilience that support the adaptive capacity of a system. Very often adaptation happens as a function of social learning wherein experience is translated into an alternative range of practice. This is in contrast with designed single equilibrium resilience in an engineered system, which, in many cases, is based on an entirely endogenous utilization of intelligence in the initial exercise of the design of the resilience performance. Therefore, the design and management of resilience processes that supports the adaptive capacity of the system and/or object is primarily centered on the capacity to internalize social and machine learning. But, adaptive capacity may also be supported by flexible governance, semi-autonomous chains of command, redundant communications pathways, readily available material and technological substitutions, and training and simulations that force responses to failure scenarios. All of these attributes may support the transformation to a new identity and function that is more likely to be adaptive than maladaptive.

Figure 2. Adaptive forms of resilience in response to novel and adverse events.

As represented in Figure 2, the intensification of hostile acts (and other non-malicious circumstantial shocks and stresses) results in the greater measure of more severe consequences. In both Figures 1 and 2, the intensification of hostile acts may also be substituted for the sheer novelty of such acts. In either case, there is a near 1:1 conceptual scaling as resilience operates in a default modulation. However, at some point in time, when there is sufficient social learning, external intelligence and/or machine learning the subject system may begin to reduce the measure of consequence as it adapts to the intensity and/or novelty of hostile acts. Indeed, with greater exposure and experience, the adaptive capacity may significantly increase proportionate to the intelligence. Of course, this assumes on some level that the adverse action has been detected.

In both Figures 1 and 2, there is no fixed measure associated with maladaptation or adaptation, respectively. Rather, these are measures of capacity for such outcomes. However, with greater degrees of social and machine learning and intelligence, there is a greater capacity for flexibility and for alternative pathways and structures that alter the identity of a system but otherwise maintain desirable processes and/or conditions.

This raises the challenging paradox of resilience in convergent cyber-physical critical infrastructure systems. On one level, the cyber domain offers a greater range of novelty for malicious acts, while, at the same time, there is a great capacity for the utilization of machine learning and artificial intelligence to create new structures and pathways that represent transformative adaptation to such novelties (Colabianchi et al. 2021). Yet, paradoxically, machine learning algorithms – and perhaps the agents of social learning – themselves must deploy a measure of resilience in order to keep up with rapid advances in computation, agent structure, and novel counterintelligence acts (Olowononi, Rawat, and Liu 2020). This raises the prospects that alternating states of resilience and adaptation may reach an absolute frontier (e.g. supercomputing) from which total and absolute failure is the only outcome in a zero-sum game.

Conclusions for guiding national resilience plans

This article has highlighted the extent to which resilience represents a strategic policy goal that provides both a front and last line of defense. It is a front-line defense by virtue of its presumed ability to serve as a CDD, and it serves as a last line of defense when dependent systems and SOSs are stressed by convergent and novel shocks and stresses. As a strategic policy goal, resilience represents a fundamental shift in a theory of national security that acknowledges the limitations of deterministic threat mitigation and conventional models of risk management. For NATO and the Allies, it also represents a critical stop-gap deterrence building measure when the rates and degrees of change (e.g. in the European theatre) are moving faster than many institutions and political processes have historically been able to keep up with. Yet, there are significant co-benefits that arise from these policies that extend beyond the military domain and well into domestic affairs.

A resilience strategy tailored to emerging threats is essential for national security and reducing vulnerabilities to acute shocks and chronic stressors alike. Such an integrated approach encourages collaboration among military, civilian, and private sectors, enhancing the collective ability to detect, respond to, and recover from threats. By adopting a comprehensive resilience framework, the Allies can enhance their adaptive capacities, ensuring they remain robust in the face of evolving challenges stemming from hybrid threats and other emerging vectors of conflict and disruption. This approach enables the identification and mitigation of vulnerabilities across critical infrastructure and minimizes the potential impact of disruptions. Furthermore, resilience planning fosters a culture of preparedness and agility within governmental and societal structures, ensuring that when disruptions occur, recovery processes are swift and effective. This strategic focus on resilience not only protects the integrity of national will but also promotes a rapid return to normalcy, thereby maintaining public confidence and societal stability.

The DOD has a great deal of experience in applying resilience across multiple sectors and domains. What it lacks is a fundamental and overarching deployment of resilience. Having such a strategic plan or policy would be arguably critical for horizontal and vertical integration across sectors and domains. In this sense, the crossover by and between military and civilian domains is intrinsically limited to a narrow area of interest. It would also be important for social learning and the integration of intelligence systems for understanding emerging and unknown phenomena and threats. By contrast, NATO has a strong strategic orientation to resilience with its emerging layered resilience framework. It simply lacks the specificity of scientific application of resilience within and across the domains. By working together, the U.S. and its NATO allies can merge bottom-up experience with top-down planning toward a more comprehensive deployment of resilience for strategic goals.

Each of the Allies has committed to developing a NRP that connects domestic and international processes, capabilities and capacities. NRPs are aligned with established Alliance resilience development priorities and an agreed-upon level of ambition for enhancing deterrence. In developing a comprehensive NRP, it is crucial to recognize the geographic factors for enablement and each nation’s risk profile, as well as the complex interdependencies that exist across various sectors and governance structures. From transportation to energy and healthcare to defense, each sector faces unique challenges, yet shares some structural underlying similarities and interconnected vulnerabilities. To craft an integrated NRP that capitalizes on these commonalities, one should align efforts in significant areas where collaborations and information can be exchanged and sustained. Given the dynamic nature of change, ongoing networks for people and information are going to need to be built alongside the NRP process. This is an important element of promoting an adaptive capacity that supports resilience.

Resilience planning requires acknowledging that SOSs, systems, and non-systems are interconnected across sectors and domains in ways that are often non-linear, unintuitive and counter to prevailing institutional wisdom. Resilience does not always lead in absolute or universal terms to advances in economic, social, or environmental welfare. It is a dynamic and adaptive process that requires resources and trade-offs that offer a pathway for a sustainable response, recovery and maybe even transformative adaptation. As noted by Adlakha-Hutcheon (2022), discovering cognition at indivudal and collective levels and forming interconnections among these elements with resilience measures–layer-upon-layer–will be key to achieving adaptive layered resilience. As the governments of NATO member nations prepare their NRPs they have the opportunity to incorporate adaptive processes that lean towards bolstering resilience in the deployment of limited and precious resources that seek to guard against a very unpredictable future.

Acknowledgments

The views and opinions expressed in this article are those of the individual authors and not those of the U.S. Army, or other sponsor or affiliate organizations of the authors.

Disclosure statement

No potential conflict of interests were reported by the author(s).

Additional information

Funding

This paper is based upon work supported by the U.S. Department of Defense Operational Resilience International Cooperation Program (DORIC) and U.S. Army Engineer Research and Development Center FLEX Project on Compounding Threats. The views and opinions expressed in this article are those of the individual authors and not those of the U.S. Army, or other sponsor organizations.

Notes on contributors

Jesse M. Keenan

Jesse M. Keenan is a Senior Economist at the U.S. Army Corps of Engineers’ Engineer Research and Development Center and the Favrot II Associate Professor at Tulane University where he conducts research in resilience and critical infrastructure systems.

Benjamin Trump

Benjamin Trump is a Senior Research Social Scientist at the U.S. Army Corps of Engineers’ Engineer Research and Development Center where he researches the intersection of resilience, engineered systems, and public health.

Eero Kytömaa

Eero Kytömaa serves as the Ministerial Adviser at the National Security Unit of the Finnish Ministry of the Interior. He has a worked extensively on countering hybrid threats and resilience policy planning in Finland and within the EU and NATO.

Gitanjali Adlakha-Hutcheon

Gitanjali Adlakha-Hutcheon serves as the Acting Chief Scientist of the Centre for Security Science and Central Offices at the Defence Research and Development Canada within the Canadian Department of Defence.

Igor Linkov

Igor Linkov is a Senior Science and Technology Manager with the U.S. Army Corps of Engineers’ Engineer Research and Development Center and Adjunct Professor at Carnegie Mellon University. He is responsible for ERDC’s project portfolio in the areas of crises management and resilience.

Appendix

Table A1. Example, non-exhaustive list of categorical forms of resilience in science.

Concept	Definition	Performance (Single Equilibrium, Multi-Equilibrium)	Adaptation	Properties and Attributes	Citation
Engineering Resilience	“A resilient engineered system is able to successfully complete its planned mission(s) in the face of environmental and adversarial threats, and has capabilities allowing it to flexibly adapt to future missions with evolving threats”	Multi-equilibrium	Yes	Flexibility, Reliable Performance	Small et al. (2018)
	“implies the ability of an engineered system to autonomously sense and response to adverse changes in health conditions, to withstand failure events, and to recover from the effects of these unpredicted events”	Multi-equilibrium	No	Anticipate, Withstand, Recover	Yodo and Wang (2016)
	.”concentrates on stability near an equilibrium steady state, where resistance to disturbance and speed of return to the equilibrium are used to measure the property”	Single Equilibrium	No	Return Speed, Steady State	Holling (1996)
Cyber Resilience	“Cyber resilience refers to the ability of the system to prepare, absorb, recover, and adapt to adverse effects, especially those associated with cyber-attacks.”	Multi-equilibrium	Yes	Absorption, Recovery	Linkov et al. (2019)
	“…the ability to anticipate, withstand, recover from, and adapt to adverse conditions, stresses, attacks, or compromises on cyber resources”	Multi-equilibrium	Yes	Anticipate, Absorption, Recovery	Bodeau et al. (2018)
	“Cyber resilience is the ability of a cyber system to recover from stress that causes a reduction of performance.”	Single Equilibrium	No	Recovery	Smith (2023)
Disaster Resilience	“the ability to prepare and plan for, absorb, recover from or more successfully adapt to actual or potential adverse events”	Multi-equilibrium	Yes	Absorption, Recovery	Cutter (2016)
	“Adaptive and integrated disaster resilience … is defined as the ability of nations and communities to build resilience in an integrated manner and strengthen mechanisms to build system adaptiveness”	Multi-equilibrium	Yes	Integration, Flexibility	Djalante et al. (2013)
	“The ability of a system, community or society to pursue its social, ecological and economic development objectives, while managing its disaster risk over time in a mutually reinforcing way.”	Single Equilibrium	No	Performance, Persistence	Keating et al. (2017)
Ecological Resilience	.”Emphasizes conditions far from any equilibrium steady state, where instabilities can flip a system into another regime of behavior – that is, to another stability domain. In this case, the measurement of resilience is the magnitude of disturbance that can be absorbed before the system changes its structure by changing the variables and processes that control that behavior.”	Multi-equilibrium	Yes	Absorb, Deform, Persistence, Transform	Holling (1996)
	“the magnitude of disturbance that can be absorbed before a system flips to another state”	Multi-equilibrium	Yes	Absorption, Transforms	Dakos and Kéfi (2022)
	“The capacity of natural systems subject to instability to absorb disturbances without shifting to a fundamentally different ecosystem domain.”	Multi-equilibrium	Yes	Absorption, Identity	Grade et al. (2023)
Community Resilience	“Community resilience is the ability of communities to withstand, recover, and learn from past disasters, and to learn from past disasters to strengthen future response and recovery efforts. This can include but is not limited to physical and psychological health of the population, social and economic equity and well-being of the community, effective risk communication, integration of organizations (governmental and nongovernmental) in planning, response, and recovery, and social connectedness for resource exchange, cohesion, response, and recovery.”	Multi-equilibrium	Yes	Withstand, Recovery, Social Learning	Keenan (2019)
	“Ability of a system, community, or society exposed to hazards to resist, absorb, accommodate to and recover from the effects of a hazard in a timely and efficient manner including through the preservation and restoration of its essential basic structures and functions	Single Equilibrium	No	Resistance, Absorption, Recovery, Return Time	Ostadtaghizadeh et al. (2015)
	“community resilience is indicated by evidence of community well-being following a disaster or crisis. Thus community provides an opportunity for a collective to adaptively cope with the experience of a potentially traumatic event.”	Single Equilibrium	Yes	Coping	Houston et al. (2015)
Psychological Resilience	“Psychological resilience is largely concerned with how people cope with adversity, psychological risk factors, and individual sensitivities to trauma”	Single Equilibrium	Yes	Coping	Davidson et al. (2016)
	“Psychological resilience is the ability to adapt positively to life conditions. It is a dynamic process evolving over time that implies a type of adaptive functioning that specifically allows us to face difficulties by recovering an initial balance or bouncing back as an opportunity for growth.”	Multi-equilibrium	Yes	Flexibility, recovery, renewal, Social Learning	Sisto et al. (2019)
	“a process in which an individual’s state or functioning bounces back to the previous level following a stressor.”	Single Equilibrium	No	Recovery	Den Hartigh and Hill (2022)
Operational Resilience	“The extent to which a firm’s operations is able to absorb and recover from disruptions”	Single Equilibrium	No	Absorption, Recovery	Essuman et al. (2020)
	“The ability of a system to adapt its behavior to maintain continuity of function (or operations) in the presence of disruptions”	Multi-equilibrium	Yes	Reliability, Continuity	Alderson et al. (2015)
	“The system’s ability to respond to and recover from an HILP event.” (High impact, low probability)	Single Equilibrium	No	Recovery	Poudel et al. (2019)
Organizational Resilience	“The ability of an organization to anticipate, respond to, recover from, and learn from adversity.”	Multi-equilibrium	No	Recovery, Social Learning	Hepfer and Lawrence (2022)
	“both the ability of a system to persist despite disruptions and the ability to regenerate and maintain existing organization”	Multi-equilibrium	No	Persistence, Renewal	DesJardine et al. (2019)
	“The ability of organizations to anticipate, avoid, and adjust to shocks in their environment”	Multi-equilibrium	Yes	Anticipate, Flexibility	Ortiz‐de‐Mandojana and Bansal (2016)
	“an organization’s ability to absorb strain and preserve or improve functioning, despite the presence of adversity”	Single Equilibrium	No	Absorption, Reliability	Kahn et al. (2018)
	“the ability of a system to minimize the financial losses associated with a disruptive event.”	Single Equilibrium	No	Minimization	Mentges et al. (2023)
Economic Resilience	“the inherent and adaptive responses to hazards that enable individuals and communities to avoid some potential losses”	Single Equilibrium	No	Avoidance, Recovery	Rose (2004)
	”…one can define economic resilience, as a combination of micro and macro-economic resilience.” “Macro-economic resilience is the ability to maintain aggregated consumption losses as small as possible, for a given amount of capital losses.” “Micro-economic resilience is defined as the ability of an economy and society to minimize household welfare losses for a given level of aggregate consumption losses.”	Single Equilibrium	No	Minimization, Withstand	Hallegatte (2014)