As the international security environment undergoes significant changes, North Atlantic Treaty Organization’s (NATO) capacity to adapt shows how alliances can evolve from focusing on military defence to encompassing a wider spectrum of regional security challenges in an integrated manner. Russia’s violation of international law in 2014, followed by the war in Ukraine, has drawn the attention of NATO to the fact that apart from diplomatic measures, there might be a need to resort to more dynamic means in order to safeguard its members’ interests, especially when the security of the alliance’s eastern flank is threatened.

NATO’s evolving role in the international security landscape reflects the alliance’s strategic adaptation to contemporary geopolitical challenges. The 2022 Strategic Concept embodies this change, emphasising NATO’s primary purpose of ensuring collective defence through a comprehensive approach focused on deterrence and defence, crisis prevention and management, and cooperative security (Calmels, 2020; North Atlantic Treaty Organization [NATO], 2022). This change occurs within a complex geopolitical context, further complicated by evolving public opinion. For example, recent trends in the United States, particularly among younger Republican congressional representatives, reveal evolving attitudes towards the support for Ukraine. With growing disapproval of President Biden’s management of the Ukraine crisis, and varying opinions on the level and duration of support for Ukraine, it is evident that public sentiment is divided and evolving (Cerda, 2023; Langer, 2023). These findings reveal the complexity of the US involvement in the Russia–Ukraine conflict and the need for policymakers to consider these diverse viewpoints when shaping the future foreign policy decisions. The shifts in public opinion can also have significant implications for the ongoing conflict (Fisher, 2020), which is expected to continue for an extended period.

This dynamic international security situation and shift in public opinion have set the stage for the ongoing challenges that NATO member states face in addressing the war in Ukraine. Consequently, there has been a significant surge in literature exploring these issues, examining them in terms of geopolitics, economics, and even psychology. Thoroughly investigating complex conflicts, such as the war in Ukraine, requires an integrative research approach, drawing on multiple research sources, including scholarly journal articles, government information resources from multiple democratic countries and international organisations, datasets, public policy research institute materials, multiple social media platforms, and public opinion polls. Researchers must navigate the strengths and weaknesses inherent in these resources while adopting an interdisciplinary methodology to comprehensively analyse these events.

This special issue of Security and Defence Quarterly was inspired by the insights from the March 2023 conference jointly organised by the War Studies University of Warsaw, Poland and the American College of Greece. The topics that were discussed address a wide range of issues, including NATO’s strategy on the eastern flank, the focus on its member states’ interdependence, the individual country challenges in the area, the defence industrial base of European countries and how they can benefit from recent developments, and even personnel psychology issues on Ukrainian battlefields. Special attention is given to the growing interest in hybrid warfare in the context of a changing geopolitical environment.

In the paper on “Conventional and hybrid actions in Russia’s invasion of Ukraine,” Ionita (2023) focuses on the need to supplement conventional operations during the war with hybrid ones, targeting both military and civilian infrastructure or blocking key maritime routes. In fact, the author argues that “the Russian invasion of Ukraine is considered a ‘strange war’ because it has used both conventional operations and hybrid warfare.” The author comes to intriguing conclusions concerning European security in the years to follow. More specifically, the paper looks at the unstable environment following the COVID-19 pandemic and the ensuing energy and food crises which are threatening to change the international world order. This affects European and Euro-Atlantic security in what the author calls a “bipolar world”: On one side are the United States and NATO with their EU allies and, on the other, the BRICS and some G20 member states, which are striving to establish their own military alliance and to replace the dollar as a reserve currency, especially in energy transactions. According to the author, the war in Ukraine thus far has shown the limited efficacy of soft diplomatic power via international organisations, such as NATO and the United Nations (UN) in averting such crises.

Given the continuing conflict and the apparent lack of compromise from both parties, the pressing questions are: How would hybrid actions and nuclear threat statements contribute to ending the war? Would the option of what is commonly called “boots on the ground” be more effective? And then the crucial question will be: Whose boots?

The issue of NATO effectiveness in resolving such critical situations is brought up in a paper entitled “Net spills among NATO allies: Theory and empirical evidence from dynamic quantile connectedness” by Palaios et al. (2023). The paper addresses the doubts expressed in the previous paper regarding the ability of NATO to resolve critical issues using soft diplomatic power. In fact, it points out that it is only during crisis that NATO member states are motivated to contribute actively to the alliance, a finding that becomes increasingly evident in relation to Russia’s invasion of Ukraine. The conclusion is based on the theory of alliances, which is expanded to consider the concept of net spills and which measures the difference between spill-in and spill-out effects between the alliance members. To assess the net spills contribution of each of the members to the alliance, the paper tests for empirical evidence of net spills among a group of NATO allies. The time-varying Dynamic Quantile Connectedness analysis applied stresses the importance of the interaction between member states of a military alliance in terms of their defence expenditure and points to the fact that there are intense incentives among the allies for free-riding behaviour. Perhaps the challenge lies in NATO members prioritising the alliance’s efficiency in dealing with international crises, such as the one going on in Ukraine, rather than focusing on their individual gains in terms of net spills.

While still addressing the alliance, the paper entitled “NATO’s strategic concept: Implications for Greece and Türkiye” (Lampas and Filis, 2023) shifts its focus to the bilateral relations of these two member states. Specifically, the paper analyses NATO’s new strategic concept in the Eastern Mediterranean. The issue is approached through a study of the frequent Greek-Turkish friction incidents and the de-escalating efforts of the alliance. The fact remains that a potential clash between the two allies could jeopardize NATO’s credibility and effectiveness given the multiple challenges the alliance faces, the leading one being the Russian invasion of Ukraine. The authors point out that such a loss of credibility could, in turn, disrupt NATO’s cooperation with other regional partners, such as Israel, Egypt, and Jordan, thereby affecting its strategic interests in the Eastern Mediterranean. Averting such adverse consequences calls for more drastic measures to be taken by NATO and other international actors aimed at a rapprochement strategy between Greece and Turkey. The problem lies in the pessimistic atmosphere that prevails. The friction between the two sides dates back to the 1960s. Since then, there has not been any convergence of opinions, despite sincere efforts from both sides. One side bases its arguments on a modern version of the “lebensraum,” while the other adheres to international treaties and legal frameworks. Perhaps the ongoing war in Ukraine will foster a compromise, uniting all alliance members. However, the potential impact of the conflict in Ukraine is yet uncertain.

The issue of economic resilience and its measurement focuses on the Central and Eastern Europe (CEE) and Black Sea countries in the framework of a comprehensive defence. The paper entitled “Measuring economic resilience for the CEE and Black Sea countries in the framework of comprehensive defence” by Constantinescu (2023) examines this specific topic in view of the developments in Ukraine and uses an economic resilience index (Hafele et al., 2023) to delineate the relative economic resilience of countries in the CEE and Black Sea region. The study presents a hierarchical ordering of the countries in the area considering potential war consequences. The author emphasises that the specific index requires further refinement to encompass social aspects as well as innovation, digitalisation, and defence-related elements. The results and conclusions must therefore be interpreted with caution due to the vague interpretation of the term “economic resilience” in the context of comprehensive defence. In addition, a selection of detailed data would add to the analysis by including more quantitative and qualitative indicator logistics, critical infrastructure, the business environment and the ease of doing business. The author concludes by highlighting that long-term resilience and stability must not be sacrificed in the pursuit of various related short- and medium-term targets.

The paper’s objective, as indicated by the author, seems to be ranking countries in the CEE and Black Sea region based on an economic resilience index, viewed through the lens of a comprehensive defence approach. The defence element is included in the analysis in the item entitled “Economic and Essential Services” as one of the comprehensive defence pillars, with the concept of comprehensive defence analysed later on.

This special issue enriches expert knowledge and presents novel insights into the complex dynamics shaping NATO’s strategic direction and its member states’ responses to contemporary security challenges. A wide spectrum of challenges facing NATO is addressed, from operational tactics and economic resilience to internal dynamics and the psychological aspects of warfare. Valuable insights into NATO’s strategic adaptations in response to the evolving security environment are provided emphasizing the need for a comprehensive approach to international security that considers both traditional and non-traditional threats. This issue not only contributes to academic discourse but also offers practical implications for policymakers and military strategists engaged in shaping NATO’s future direction.