Space is a rapidly evolving environment which is essential to NATO’s deterrence and defense. As of 2019, NATO has recognized space as an operational domain, alongside air, land, maritime, and cyberspace. At the same time, space is becoming more vulnerable to interference and threats as some countries such as Russia and China are developing and testing a variety of counter-space capabilities.

NATO and other armed forces are increasingly reliant on space-based assets for communication, intelligence, surveillance, positioning, navigation, and timing, making space an essential component of modern military operations. NATO, in particular, depends on space for core functions such as positioning, navigation, and timing, integrated tactical warning and threat assessment, environmental monitoring for mission planning, satellite communications, and intelligence, surveillance and reconnaissance (NATO 2025). 

However, the space security environment is evolving rapidly, with a growing number of actors capable of launching and operating spacecraft, as well as developing and accessing advanced technologies and services (NATO 2025). While these developments present new operational opportunities, it also introduces significant risks, vulnerabilities, and potential threats. Adversaries, notably China and Russia, have been developing and testing a wide range of counter-space capabilities that could limit NATO Allies’ access and freedom of action in space (NATO 2025). This raises the threat of attacks on both civilian and military space infrastructure, and potentially undermines security and commercial interests (NATO 2025). 

Since 2019, when Outer Space was formally recognized as an operational domain, alongside land, air, maritime, and cyberspace, NATO has increasingly acknowledged the need to protect and ensure resilient access to space while remaining fully in line with international law (NATO 2025). 

This brief introduces two policy options: Policy Option 1 that advises to maintain strategic ambuigity through deterrence by threat of retaliation and Policy Option 2 that advises NATO to improve and increase its resilience in counter-space attacks through detererrance by denial. Ultimately, this brief recommends that NATO attend to Policy Option 2 due to the legal and operational uncertainties of invoking Article 5. 

1. Policy Options 

1.1 Policy Option 1: Maintain Strategic Ambiguity Through Deterrence by Threat of Retaliation 
In the 2019 Space Policy adopted and implemented by NATO, “Allies have agreed that attacks to, from, or within space present a clear challenge to the security of the Alliance, the impact of which could threaten national and Euro-Atlantic prosperity, security, and stability, and could be harmful to modern societies as a conventional attack. Such attacks could lead to the invocation of Article 5. A decision as towhen such attacks would lead to the invocation of Article 5 would be taken by the North Atlantic Council on a case-by-case basis” (NATO 2025). 

By maintaining strategic ambuigity regarding the invocation of Article 5 in outer space, NATO discourages potential adversaries from engaging in hostile acts and keeps one uncertain about the threshold for collective defense (Ören 2024, p. 4). It sends a clear signal that hostile actions by potential adversaries could be met with a strong, coordinated, and unified response by NATO, thus deterring aggressive, and destabilizing acts by adversaries (Ören 2024, p.4). 

While Article 51 of the Charter of the United Nations grants the right to individual or collective self-defense against an armed attack, the challenge towards the invocation of Article 5 lies in Article 6 (Bednar 2024, p. 435). Article 6 has geographical implications for the invocation of Article 5. An armed attack carried out “on the territory of any of the Parties in Europe or North America, on the Algerian Departments of France, on the territory of Turkey or on the Islands under the jurisdiction of any of the Parties in the North Atlantic area north of the Tropic of cancer; or on the forces, vessels, or aircraft of any of the Parties, when in or over these territories or any other area in Europe in which occupation forces of any of the Parties were stationed on the date when the Treaty entered into force or the Mediterranean Sea or the North Atlantic area north of the Tropic of Cancer” (NATO 1949). The treaty does not mention any relation to outer space, or of satellites which brings into question the legal implications of triggering Article 5 to outerspace (Mackie 2023, p. 82). 

From one perspective, NATO’s approach represents a bold strategic move to increase ambiguity around the scope and application of collective defense in emerging domains, which in turn, can prompt adversaries to proceed with greater caution. From another perspective, however, it reflects the challenges NATO faces as it adapts collective defense to a new operational domain (Mackie 2023, p. 83). Because space as an operational domain is still relatively new, this domain lacks clear boundaries and established legal norms, which can cause NATO’s position to be perceived as lacking resolve (Mackie 2023, p. 83; Sari & Nasu 2021, p. 41). 

Additionally, ambiguity also persists regarding how the right to self-defense applies in space (Sari & Nasu 2021, p.41). For instance, it remains unclear whether non-kinetic interference such as signal jamming reaches the threshold of an “armed attack” to invoke Article 5 (Sari & Nasu 2021, p.41). Moreover, Article 6 of the North Atlantic Treaty complicates matters even further. Article 6 has geographical constraints that limit Article 5 to attacks occurring “in or over” Allied territory (Bednar 2024, p. 437). Article 6’s language on ‘forces’ creates uncertainity about whether attacks on satellites outside NATO

territory would trigger Article 5. While the term ‘forces’ outlined in Article 6 could arguably include spacecraft and their personnel, the second sub-paragraph of Article 6 implies that Article 5 would only be applied when attacks on space assets are orbiting above NATO member territory (Sari & Nasu 2021, p.41). This could enable adversaries to exploit legal “grey zone” actions, such as targeting an Allied satellite while it is passing over non-NATO territory (Sari & Nasu 2021, p.41). 

1.2 Policy Option 2: Deterrence by Denial 
A second policy option is for NATO to adopt a strategy of deterrence by denial, particularly through improving interception and resilience of its space systems. Deterrence by denial seeks to discourage an adversary from attacking by convincing them that the attack will not succeed (Peace 2023, p. 61). Drawing on Mearsheimer’s logic of conventional deterrence, rational actors weigh the costs and benefits of their actions, therefore, if NATO can ensure that any attack on its space infrastructure is likely to fail, a rational adversary will reassess the value of launching such an attack (Peace 2023, p. 61). In this regard, deterrence by denial seeks to undermine the adversaries’ expected military gains by interrupting the attack before it can achieve its objective (Koplow 2019, p. 32). 

NATO currently relies heavily on member states, commerical companies, and the NATO Communications and Information Agency (NCIA) for most of its space-based products, services, and data (NCIA 2023). While this strategy reduces financial costs, it also introduces strategic risks. Dependence on external actors such as commercial companies, can create a dependency dilemma, in which external actors may fail to provide and assist NATO requests, and it may face blurred boundaries between military and civilian boundaries (Satta 2025). Such dependence also introduces NATO to vulnerabilities related to security, defense, and operational control (Satta 2025). 

Developing and improving NATO-owned resilient space capabilities would reduce these vulnerabilities and potentially increase NATO’s ability to deter attacks by denial. Increased resilience through decoys, redundancy through satellite constellations, and hardening satellites against jamming can improve communications, protect critical infrastructure systems, and improve the accuracy and reliability of positioning, navigation and timing information (Sari & Nasu 2021, p. 42-43; Peace 2023, p. 62). By limiting the effectiveness of attacks through deterrence by denial, NATO would make adversary attacks unsuccessful, lower the expected benefits for adversaries, strengthen deterrence, and limit the security risks of relying on external actors (Ören 2024, p. 9). However, improving and increasing interceptive space assets to counter threats to space-based capabilities will be extremely costly (Koplow 2019, p. 40). Despite this constraint, by making attacks uncertain, and unlikely to succeed, NATO can reshape adversaries’ expectations of successful attacks. 

2. Policy Recommendation: Deterrence by Denial 
Based on the analysis of both policy options, NATO should prioritize Policy Option 2: Deterrence by Denial. While maintaining strategic ambiguity through the threat of retaliation offers deterrent effects, it is limited by legal and operational uncertainties, including the unclear invocation of Article 5 to attacks in space, the threshold for non-kinetic interference, and potential exploitation of legal ‘grey zone’ operations by adversaries. In contrast, deterrence by denial strengthens NATO’s credibility by decreasing vulnerabilities and increasing resilience. Expanding NATO-owned space capabilities through hardened satellites, redundant satellite constellations, decoys, and improved interception measures, will not only undermine the expected benefits of adversaries launching attacks but will also lower the likelihood of the attacks being successful. This approach also reduces risks associated with dependence on commercial actors, such as supply failures, blurred military and civilian boundaries, and limited operational control. Although this approach would be financially costly, the long-term strategic outcome would be significant, as it would provide NATO with a credible and sustainable deterrent and defense posture that protects critical space-based assets and ensures the Alliance’s operational effectiveness in this new emerging domain. 

3. Conclusion 
Space has become a critical operational domain for NATO, underpinning essential military capabilities such as communications, intelligence, surveillance, and navigation. At the same time, the evolving space security environment, with the emergence of counter-space capabilities from adversaries such as Russia and China have introduced new risks and vulnerabilities. This policy brief has evaluated two options for NATO’s response: maintain strategic ambiguity through deterrence by threat of retailation, and strengthening resilience through deterrence by denial. While ambiguity can provide deterrent value, it is constrained by legal uncertainties, operational limitations, and potential legal ‘grey zone’ tactics. Deterrence by denial, on the other hand, although costly, offers an approach that reduces vulnerabilities, safeguards critical assets, and shapes adversary strategic decisions-making By investing in hardened satellites, decoys, redundant satellite constellations, and improved interception measures, NATO can establish a credible and sustainable deterrent and defense posture that ensures operational effectiveness, protects key space-based assets, and reinforces NATO’s strategic advantage.

4. Bibliography 
Bednar, D. (2024). Implementation of NATO’s Space Policy - Fundamental Legal Issues. The Lawyer Quarterly, 14(4), 433-447. 

Koplow, D.A. (2019). Deterrence as the MacGuffin: The Case for Arms Control in Outer Space, Georgetown University Law Center, 1-82. 

Mackie, S. (2023). The North Atlantic Space Schism and the Ambiguity Problem: NATO’s Collective Space Defence Posture. Air and Space Power Review, 25(2), 72-92. 

NATO (1949, April 4). The North Atlantic Treaty. https://www.nato.int/en/about-us/official-texts-and-resources/official-texts/1949/04/04/the-north-a tlantic-treaty 

NATO. (2025, July 30). NATO’s Approach to Space. https://www.nato.int/en/what-we-do/deterrence-and-defence/natos-approach-to-space

NCIA. (2023). Space. https://www.ncia.nato.int/about-us/technology-and-innovation/space 

Ören, A. (2024). Innovating Deterrence Strategies in the New Space Age. Journal of Aviation and Space Studies, 4(3), 1-12. 

Peace, A.N. (2023). Space Denial: A Deterrence Strategy. Joint Force Quarterly 111, 4, 58-66. Sari, A. & Nasu, H. (2021). NATO And Collective Defence in Space: Same Mission, New Domain. TransAtlantic Policy Quarterly, 2(20), 35-43. 

Satta, M. (2023, September 13). The Privatisation of Persistent Surveillance. Risks and Opportunities for NATO’s Space Strategy. Atlas Institute for InternationalAffairs.https://atlasinstitute.org/the-privatisation-of-persistent-surveillance-risks-and-opportunitie s-for-natos-space-strategy/?utm_source=chatgpt.com