National Interest

by Andreas Umland

    At the end of the day, Western promises of support for Ukraine cannot replace a strong Ukrainian military as an effective deterrent to Russia.

    Since spring 2025, the term “security guarantee” has become a buzzword in international debates about future Western support for Ukraine. Following the conclusion of a ceasefire, ensuring Ukraine’s security is to be a central component of international engagement with the embattled country. However, the term is currently often used in a way that leaves important political and strategic challenges to the implementation of these guarantees unaddressed.

    In general, the term “security guarantees” can be misleading: a complete security guarantee is an unattainable illusion, not only for Ukraine but also for every other nation. Expert discussions distinguish between guarantees and (weaker) security commitments, as well as between positive and negative guarantees. As a rule, a positive security guarantee—the type of promise Ukraine is seeking—implies strong commitments on the part of the guarantor to protect the beneficiary.

    The different definitions and interpretations of security guarantees, as well as the ambiguities and contradictions implicit in their planning and implementation, pose a problem. Open questions must be clearly identified at the outset. Transparency can help move from purely discursive progress on Kyiv’s future defense needs to a real improvement in Ukraine’s security situation.

    There is a risk that the promise that the term “security guarantees” seems to offer will ultimately not be kept. While security guarantees were the subject of intense debate in Europe and beyond in 2025, the specific future challenges they pose remain unclear. Inconsistent implementation of loudly proclaimed support and defense commitments would not only be dangerous for Ukraine but also undermine the already shaken European security order and the rules-based international system.

•     The Dilemma of a European “Reassurance Force”

    One approach to ensuring the stability of a future ceasefire is contained in the European idea of a so-called “reassurance force.” This plan was conceived in the spring of 2025 and includes, among other things, the deployment of several tens of thousands of ground troops on Ukrainian territory and the dispatch of warships to the Black Sea from some of the 33 member countries of the so-called Coalition of the Willing (CoW).

    The “reassurance force” would be a central part of this coalition’s larger effort to stabilize a future ceasefire. It would rely on limited assistance from the United States. This could include air support, intelligence exchanges and logistical capabilities, but no US troops on the ground.

    However, the commendable European plan for a Western “reassurance force” in Ukraine suffers from two strategic paradoxes. First, the current public discussions about Western troop deployment in Ukraine are counterproductive to the negotiations between Russia and Ukraine on a ceasefire. As much as the idea of a Western “reassurance force” in Ukraine is welcomed, Russia rejects the prospect outright.

    So far, public discussion of the “reassurance force” has made a compromise-based ceasefire with Russia even more distant. It has strengthened Moscow’s commitment to its war of aggression, thereby intensifying the economic and military pressure needed to persuade the Kremlin to accept a truce.

    The second strategic paradox of the plan stems from uncertainty regarding a worst-case scenario in which the “reassurance force” would be involved in active combat with the Russian military. The most difficult question surrounding the possible deployment of Western ground troops in Ukraine would be how they would respond if they were attacked by, for example, Russian missiles and drones, resulting in significant human and materiel losses. The response to such an incident would not only pose a military dilemma but also trigger far-reaching political consequences.

    If the “reassurance force” were to respond congruently to a Russian provocation, the participating countries, as well as NATO and the EU, could become embroiled in a Russo-Ukrainian War. If, on the other hand, the “reassurance force” fails to respond adequately to a Russian attack, the mission would lose its meaning and the West’s general willingness to engage in collective defense may be called into question.

• The SkyShield Plan: US and European Air Support for Ukraine

    Is there nevertheless a form of direct military support that the CoW can provide beyond material, financial and cognitive assistance to the Ukrainian armed forces  A limited engagement of their air forces over and in western and central Ukraine appears less problematic than the deployment of ground troops and warships. Such support with Western interceptors—also known as “SkyShield”—would already be possible and sensible now, before a ceasefire is concluded.

    The establishment of joint air defense zones over entire regions of Ukraine, or at least over important cities such as Uzhhorod, Lviv and Kyiv, or critical infrastructure, carries less risk of escalation, as the deployment of Western interceptors can be limited in two ways.

    First, Western involvement in Ukraine’s air defense could be agreed upon so that it occurs only over Ukrainian territory, far from the current combat zones and the Russian-Ukrainian border. Second, this geographical restriction of jet operations to the hinterland of central and western Ukraine means they will not encounter manned Russian aircraft or helicopters. Western interceptors or anti-aircraft drones and missiles would only shoot down Russian unmanned aerial vehicles and would not endanger Russian soldiers or violate Russian airspace.

    Clear and well-defined security guarantees are not the only prerequisite for a future ceasefire to work, but they are a key one. However, the principally laudable idea should be implemented with caution: it should not raise expectations that cannot be met, nor should it falsely give the impression that the West’s involvement in Ukraine would change qualitatively after the end of the war.

    In a few years, circumstances may change and foreign troops in Ukraine and maritime engagement in the Black Sea may prove less problematic. Under today’s conditions, however, debates about the deployment of a “reassurance force” in Ukraine distract from more important issues. After all, the decisive guarantor of Ukraine’s security is and will remain its own armed forces. Moscow’s aggression can only be contained by a Ukraine armed to the teeth and possessed of a large professional military, a condition that applies in times of both war and peace.

    When designing security guarantees, the focus should be on those instruments that can be realistically and quickly applied after the start of a ceasefire. Furthermore, planning security guarantees for the post-war period should not distract from the primary task of first creating the conditions for an end to the fighting and enabling the start of at least a partial ceasefire. Many of the instruments that can today contribute to ending the war will also be crucial to maintaining peace in the future.