Ayesha Munshi
NATO often presents its post Cold-War expansion as one of its great successes with new members, most recently Sweden and Finland, often framed as proof of NATO’s enduring relevance. Yet Europe is currently defined by increased militarisation, proxy conflict and rigid borders. As NATO continues to expand, the question is no longer whether expansion strengthens the alliance, but whether it undermines the very stability it aims to secure. By protecting its members, NATO expansion leaves non-members exposed, turning security for some into instability for many.
NATO argues that enlargement is defensive, voluntary and driven by states seeking protection against external threats and wanting to secure political stability. This argument gains credibility after Russia’s invasion of Ukraine in 2022. Finland and Sweden joining the alliance soon afterward further reinforced the claim that NATO expansion deters aggression towards vulnerable states. From this perspective expansion is not only logical but necessary.
However this overlooks the fundamental issue that states who are not part of this alliance may see increased militarisation as a threat, which deters diplomatic ties. NATO expansion may guarantee security to its members under the Article 5 commitment to defending each other, but it also reshapes the environment for those outside this alliance. As NATO adopts “the most comprehensive and detailed defence plans since the Cold War”, Russia is likely to view it as explicitly hostile. While this does not justify Russian aggression, it makes confrontation increasingly predictable.
NATO claims its expansion is not meant to threaten the Russian Federation and that increased militarisation in Europe was a response to Russia’s invasion of Ukraine. An official claim before 2022 stated, “NATO does not seek confrontation and poses no threat to the Russian Federation.” At the same time, Russian officials insist that NATO expansion is a direct threat to their national security.
Russian Ambassador to the U.S., Anatoly Antonov, stated that NATO’s efforts to build up defences in former Soviet republics are unacceptable and increase the risk of escalation and direct military clashes. This situation reflects a classic security dilemma when one state takes action to protect itself, others perceive it as a threat, prompting countermeasures that leave everyone worse off. As a result, NATO members may feel secure, but that security comes at the cost of heightened insecurity elsewhere.
The case of Ukraine exposes the limits of this approach. NATO signaled possible future membership to Ukraine, but no concrete steps were taken toward its membership, with President Volodymyr Zelensky saying that the “open door” rhetoric is not enough. This ambiguity placed Ukraine in a grey zone, where it was neither neutral nor fully protected. When Russia invaded, NATO’s reaction revealed a harsh reality: states that are not members are left vulnerable, receiving only symbolic support.
At the same time, NATO has emphasized that its support for Ukraine is fully consistent with international law. The alliance recognizes Ukraine’s right to self-defense under the UN Charter and has worked to strengthen its ability to defend sovereignty. The 2024 Washington Summit reaffirmed NATO Allies’ support for Ukraine’s path to membership and established the NATO Security Assistance and Training for Ukraine (NSATU) program to coordinate military equipment and training.
NATO stresses that Ukraine, like any country, has the right to choose its own security arrangements free from outside interference, and Russia does not have a veto over its future. By supporting Ukraine, NATO claims it is upholding the international rules-based order while ensuring the security of one billion people across the Alliance.
The fact still remains, that expansion and security reinforcement can be perceived as a threat and that blocs increase polarisation, often leading to escalating issues and leaving non-members vulnerable. The deeper issue is not whether NATO should expand, but what that expansion leads to.
Enlargement has become NATO’s default response to insecurity, leaving little room for alternative approaches such as arms control and regional cooperation. By treating expansion as synonymous with peace, the alliance avoids confronting how blocs deepen divisions and limit diplomacy. Growth symbolises success even when underlying issues intensify.
If NATO’s future is defined by how far it can expand, the alliance risks confusing growth with lasting security. Stability cannot be achieved through enlargement alone, it requires infrastructure capable of managing rivalry without constantly turning it into a military standoff.
NATO’s challenge is not just to defend its members, but to rethink how security can produced in a world that is deeply divided. Expansion may offer protection, and supporting allies like Ukraine upholds international law, but without equal focus on diplomacy, de-escalation, and global trust, it may ensure long-term instability remains a part of the international order.
The author is a scholar at the Aga Khan University, Faculty of Arts and Science program. She is majoring in Politics, Philosophy and Economics, and holds a special interest for international relations, wishing to pursue a career in the field.
