European military deployment in Ukraine?

Almost from the very moment President Trump launched his campaign to end the war in Ukraine on the terms dictated by him, France and Great Britain have been particularly active in what appears to be an attempt to prove that the international legality to which we were accustomed is still in force, that Europe has effective autonomous agency capacity in security subject , and that they are capable of exercising the leadership that the United States would have abandoned.

As a central part of that effort, both countries have announced their intention to organize and lead a military operation comprised of contributions from a coalition of willing nations, which would have a deterrent (reassurance force) character and would deploy after a cease-fire has been reached between Russia and Ukraine.

European partners have welcomed the initiative with varying enthusiasm. All, one must think, embrace the general principle of respect for the sovereignty of states which justifies moral and material support for Kiev; but not all are willing to go to the same lengths in its defense, and some even consider that, without American backing, the only realistic alternative is to invoke pragmatism and accept Washington's plan, however repugnant it may seem.

As if this were not enough, the very lack of definition of the project fosters skepticism among potential contributors. The first doubt it raises concerns the goal that such a force should achieve: would it be an interposition force, should it persuade Russia to respect the cease-fire? In reality, it is not clear what is intended, nor is the legitimacy that would give it cover, nor the specific missions it would have to carry out in order to fulfill this mission statement.

The answer to these unknowns depends on the definition of central issues such as the entity, configuration, material, deployment of units, or prescriptions on the use of force, so that they are consistent with what is required of them in the real environment they encounter on the ground. Without concreteness on these issues, mission statement can easily be derailed by a mismatch between tasks, capabilities and possibilities, with serious consequences ranging from damage to Europe's credibility as an international actor to the fatal involvement of the force in high-intensity combat for which it may not be adequately equipped.

The question of legitimacy is also central. Evidently, after the Russian aggression, it can be argued that the proposal intervention is legitimized as an exercise of collective self-defense and to put an end to violence; However, and leaving aside the discussion on the validity of the principle, respect for the still commonly accepted international legality demands that the UN Security committee pronounce itself on the matter and issue a resolution authorizing the deployment of a military force to fulfill one of the missions foreseen in chapters six and a half and seven - peacekeeping or peace enforcement, respectively - of the UN Charter.

In the case of peacekeeping, the precondition for deployment is that a peace agreement acceptable to both parties is reached, and that both consent to the presence of the force. To think that Russia, which invaded Ukraine to avert the possibility of NATO extending its presence on the other side of its borders, is going to accept, without further ado, the presence in the neighboring country of forces from those same countries seems complicated. Assuming that Russia - a party, but also a judge in the case thanks to its permanent seat in the UN Security committee - accepts the presence of such a force, it would be advisable not to lose sight of the fact that experience sample that consent can be revoked or not accepted locally, so that a peace status can soon turn into one of direct hostility towards the contingent carrying out the peace operation.

In the case of deployment in a peace enforcement mission statement or, as seems to be the case, as a deterrent to ensure a cease-fire, consent is not necessary for legitimacy purposes, but the agreement of the Security committee is necessary, virtually impossible in this case without Russia's affirmative vote. In the absence of this consent, the force deployed would become a belligerent in the eyes of non-consenting actors, who would see it as a military goal . If, in this case, a unit of a NATO country were to receive a deliberate attack from Russia, could that country invoke article 5 of the Washington Treaty? In that case, what could happen, could an escalation with an unforeseeable end follow?

Finally, it is just as important to provide the deployment with sufficient credibility (which implies, on the one hand, political will on the part of the participants to sustain the deployment as long as necessary, even in the event that the status changes for the worse) as it is to put together a robust contingent, capable of imposing itself on the parties even in the most adverse circumstances. That means armored and mechanized units in sufficient numbers for the mission statement to be decided upon, fire support, anti-aircraft and anti-missile defense, capable and reliable communications and intelligence, a robust command and control system, full logistical support, and a reservation powerful enough to respond adequately to any contingency. The question is whether the coalition countries that France and Britain seek to arm would be able to meet these needs convincingly without U.S. partnership . Given the current state of European defense, the conclusion is left to the reader.

These are not minor challenges that this initiative must overcome. If the issues outlined here, and others of similar importance, such as the definition of the desired final status to initiate redeployment, are not sufficiently clarified, the project will be doomed to failure, which would damage, perhaps irreparably, Europe's already battered credibility or, worse still, could lead to a major fiasco with avoidable casualties.

Spain, for the time being, remains on the sidelines of the project, adopting a passive attitude while awaiting further definition. It is not the purpose of this article to pronounce on what our country should do in this regard. Whether or not it decides to participate, it should take seriously the important shortcomings that long years of budgetary drought have caused in national defense in order to rectify them for its own benefit and that of its European allies and partners, persuaded that a protagonist, active and supportive attitude in collective defense is a core topic reinforcement of its own security.

* This text by Salvador Sánchez Tapia, Brigadier General (R) and GASS researcher , was first published in the online edition of the ABC newspaper on April 3, 2025.