Start / Publikationer / Securing Ukraine: NATO, Security Guarantees, and Weapons

SCEEUS Report No. 8, 2023

Executive Summary

The West’s military assistance to Ukraine since Russia’s invasion in February 2022 has been substantial. But there is still no long-term strategy to secure Ukraine and prevent Russia from again attacking Ukraine in the future. Russia has not given up on its objectives of subjugating Ukraine and is unlikely to do so for the foreseeable future. Unless deterred, Russia will continue to pose a threat to Ukraine irrespective of the outcome of the war.

Russia’s invasion of Ukraine has fundamentally changed Europe’s geopolitical reality. There is no longer any security or stability in the geopolitical grey zone between NATO and Russia. Only NATO membership will provide security for Ukraine and long-term stability for Europe. But how to make Ukraine a member while the war is going on?

NATO Allies should at the summit in Vilnius commit to a roadmap that sets out a clear and accelerated process for Ukraine to become a NATO member. This should be complemented with a commitment to building up and sustaining Ukraine’s military capacity over the long term. A coalition of Western states should also commit to using air power to defend western Ukraine from any new attack by land. These steps would help to protect Ukraine against future Russian attacks until it becomes a NATO member.


Russia’s war against Ukraine has raised the fundamental question of how to secure Ukraine and stabilise Europe over the long term. Western military support to Ukraine since the start of the invasion has been substantial and helped the country defend itself and retake some territory. But the West still does not have a long-term strategy to secure Ukraine. Irrespective of how the war ends, the critical question of how to prevent Russia from attacking Ukraine in the future remains unanswered.

Putin’s objective in waging war against Ukraine – the subjugation of the Ukrainian state and nation – has not changed despite Russia’s military setbacks. This objective is likely to remain unchanged at least as long as Putin remains in power. But this maximalist objective and the brutality of Russia’s war in Ukraine have fundamentally changed Europe's geopolitical reality. 

The war has shown that there is no security for states in the geopolitical grey zone between NATO and Russia. Rather than being a “buffer”, the grey zone is a source of instability. Instead of providing safety, “neutrality” makes countries vulnerable to Russian aggression. This was the conclusion drawn by Sweden and Finland after 24 February 2022. Europe will be characterized by instability as long as Russia considers military force as a viable option for coercing countries in the grey zone into its sphere of influence.

Russia’s war against Ukraine is leading to a fundamental shift in thinking about Ukraine’s place in European and Euro-Atlantic structures. The historic decision by the European Council in June 2022 to grant Ukraine candidacy status is testament to this. The decision is a strong repudiation of Moscow’s ambitions in Ukraine and a signal that Ukraine is part of the West. The decision also represents a geopolitical commitment to Ukraine’s future security and prosperity. But without a strategy to secure Ukraine, this commitment could end up being an empty promise.

Discussions on NATO membership for Ukraine have also undergone a substantial shift since the start of the invasion. Once a taboo, NATO membership for Ukraine is gaining increasing support among Allies; this discussion is intensifying ahead of the NATO summit in Vilnius in mid-July. In parallel, key capitals are discussing a formula to provide robust commitments to help Ukraine build up and sustain its military capacity over the long term. Some of Ukraine’s key partners, such as France and the UK, have explicitly stated their readiness to support security guarantees for Ukraine to help it defend itself and to prevent future Russian aggression.[1] The key challenge, however, is how to effectively secure Ukraine without risking a larger war between Russia and the West.

Securing Ukraine

Regardless of whether Ukraine succeeds in pushing out Russian troops from its territory or whether the war transforms into a protracted stalemate, Russia is likely to rearm and reconstitute its forces in order to attack Ukraine again in the future. This is why accepting a ceasefire now would not resolve the conflict but rather provide Russia with time to prepare to attack Ukraine again in the future. According to US estimates, Russia would need 5-10 years to build up its military capabilities to levels prior to 24 February 2022.[2]

How can Europe deter and dissuade Russia from attacking Ukraine again in the future? When Ukraine becomes a member of the EU, it will be covered by the mutual defence clause – Article 42.7 – in the Treaty of the European Union.[3] The language of the article is strong, arguably stronger than Article 5 of the North Atlantic Treaty. Nevertheless, the absence of the United States and the lack of joint military planning and military structures in the EU limit its ability to deter Russia from attacking Ukraine again. Notwithstanding the mutual defence clause, the EU is still not a defensive alliance in practical terms. Moreover, the need to secure Ukraine arises before Ukraine becomes an EU member.

NATO membership for Ukraine remains the most effective way to deter Russia. Russia respects NATO and takes Article 5 seriously. During the Cold War, the Soviet Union was deterred from attacking NATO Allies because it knew that the military response would be devastating. Since 1991, Russia has also avoided military confrontation with NATO including new NATO Allies on its border, such as the Baltic states. Since the start of the invasion in February 2022, Russia has been exceedingly careful to not let the war spread to NATO members. When missiles have strayed into NATO territory, Moscow has been quick to deny any involvement and tried to deescalate tensions.[4] Moscow understands that a large-scale war with NATO would be catastrophic.

The reason Russia has opposed NATO membership for Ukraine and Georgia since the Bucharest summit in 2008 was that Moscow sees membership as preventing its imperialistic ambitions in those countries. The prospect of NATO membership was not the cause of Russia’s wars in Georgia and Ukraine. The cause was Russia’s imperial ambitions. Russia was opposed to NATO membership since it would thwart those ambitions.

Discussions on inviting Ukraine to become a NATO member have intensified in the run-up to the NATO summit in Vilnius. Ukraine is pushing to receive an invitation at Vilnius, but there is reluctance in some key capitals about extending an invitation to Ukraine.[5] They see membership as increasing the risk of a direct military confrontation between NATO and Russia.

But this logic is flawed. Bringing Ukraine into NATO would ultimately be a way to deter Russia from attacking Ukraine. Article 5 guarantees for Ukraine would provide deterrence against a Russian attack and inject much needed predictability into the West’s relationship with Russia. It would end any ambiguity about Ukraine’s future trajectory and place in the global order. In this way NATO membership for Ukraine would provide stability rather than instability.

Prior to 2014, neutrality may have provided security for Ukraine. But Russia’s annexation of Crimea and attack against Ukraine in 2014 exposed the vulnerabilities of neutrality. Russia’s invasion in February 2022 demonstratively proved that there was no security in neutrality. Russia’s invasions of Ukraine have shattered any remaining illusion of security outside of NATO. The uncertainty of the grey zone is now a source of instability in Europe because it opens the door to Russian aggression. This is the fundamental lesson of Russia’s war against Ukraine.

Even the arche-realist Henry Kissinger has changed his mind about Ukraine and NATO membership. Prior to Russia’s invasion, he argued that Ukraine should be neutral; now he argues that the only way to provide safety for Europe is for Ukraine to join NATO. In part this is due to Russia no longer posing the same conventional threat as it did prior to the invasion. He also believes that NATO membership for Ukraine would provide safety for Russia.[6]

How to Get There?

The conundrum is how to move forward on NATO membership for Ukraine while the war is ongoing. Making Ukraine a NATO member during the war risks drawing NATO into an immediate military confrontation with Russia since Ukraine is under constant attack by Russia and part of Ukraine’s territory is under Russian control.

What is needed is a decision on a clear and accelerated process that moves Ukraine towards NATO membership. The Vilnius summit provides an opportunity for Allies to go beyond the commitment made at Bucharest and agree on a roadmap towards membership with a firm commitment to extend an invitation to Ukraine. The roadmap should set out how NATO Allies can provide practical support to Ukraine in moving forward along this roadmap. The roadmap should not set out conditions for membership but rather provide a political path to membership. Part of this roadmap should include transforming the NATO-Ukraine Commission into a NATO-Ukraine Council and giving Ukraine the right to participate in meetings of the North Atlantic Council.

Until now, Ukraine has been stuck with NATO’s open-door policy and the unfulfilled promise of membership in Bucharest in 2008. This was the worst of all worlds as it exposed Ukraine (and Georgia) with devastating and destabilising consequences. There has been no way for Ukraine to move forward, especially since it has been blocked from receiving the Membership Action Plan (MAP).

The idea that MAP would be a roadmap to membership has largely been overtaken by events. At Vilnius, Allies should make clear that MAP is no longer a prerequisite for membership. Ukraine may not have achieved full interoperability with NATO but, even so, has proven its ability to carry out NATO's “core business” to a greater extent than many NATO allies. Ukrainian forces now have more experience and knowledge of using NATO weapons in combat than most allied troops. Ukraine has acquired one of Europe's most capable land forces and, as a NATO member, would significantly strengthen the Alliance’s eastern flank.

In many areas, such as the use of combat drones, Ukraine has gained experience from the battlefield that will contribute to further developing NATO protocols and concepts of operation. In these areas, Ukraine has gone beyond interoperability, and NATO will have to adapt to the lessons that Ukrainian armed forces have learnt. Interoperability as a prerequisite for membership appears today as a technical hurdle that has been overtaken by the reality of war. Ukraine can continue to adopt NATO standards and enhance interoperability after becoming a NATO member.

There is a trap that should be avoided at Vilnius. This is the conditional invitation, i.e. stating that Ukraine will be invited when the security situation allows or when the war has ended. Such a formula would create an incentive for Moscow to never stop fighting. It would also give sceptical Allies an excuse to continue blocking an invitation if, for instance, Crimea is still under Russian control. A formula should be found in Vilnius that does not offer Russia a de facto veto on Ukraine’s membership.

A Geographically Limited Article 5

The circumstances under which NATO extends an invitation to Ukraine is a crucial consideration. The ideal circumstances would be a strategic defeat for Russia in which Ukraine has pushed out all Russian forces and Russia is practically and politically incapable of attacking Ukraine again for the foreseeable future. Such a situation is likely to last only a few years since Russia would seek to rearm and reconstitute its forces. But it would allow Ukraine to become a NATO member without a Russian military response that would trigger a NATO-Russia war.

But what if the war ends up in a more ambiguous scenario: a protracted stalemate in which Russian forces remain in parts of Ukraine, i.e. a situation in which both sides are exhausted and incapable of making territorial gains on the battlefield? In such a “Korea scenario”, NATO membership could initially come with a geographic limitation on the Article 5 mutual defence clause. The exact geographic limit would depend largely on where the contact line is at the time. Based on the current contact line, Article 5 could, for instance, cover the territory west of a Kherson-Dnipro-Kharkiv axis.

Geographic limits on security guarantees have a precedent in West Germany’s membership of NATO.[7] In 1955, Chancellor Konrad Adenauer and the West were faced with a choice between possible unification of Germany (but under the condition that it would be neutral and demilitarised) or security for West Germany as a member of NATO but then continued division. Adenauer made a strategic bargain choosing security and division with a view to unification at some distant point in the future.

Article 5 with geographic limits would not entail “giving up” on eastern Ukraine or de facto accepting a Korea-style division of Ukraine. Such an arrangement should make sure to not indirectly legitimise Russia’s control over the east. Western powers would still support Ukraine’s military efforts to retake its territory and restore its territorial integrity. NATO membership and limited Article 5 coverage would be on top of other forms of support not least building up Ukraine’s military capabilities over the long term. NATO could commit to extending Article 5 coverage when Ukraine takes back its territory.

The security umbrella provided by Article 5 over western Ukraine would create space for reconstruction and reform. It would help overcome the hesitation by the private sector to take part in the reconstruction of Ukraine because of the security situation. Article 5 coverage would enable foreign direct investment and create more conducive conditions for Ukraine to move forward on the EU accession path.

Bringing Ukraine into NATO with geographic limitations on Article 5 presupposes a situation in which Russia has stopped attacking western Ukraine with missiles and drones as this would constitute an attack and trigger Article 5. If such attacks continue, partial security guarantee by an ad hoc grouping of states could be envisaged as an interim measure.

Partial Security Guarantees

NATO membership for Ukraine will in all likelihood take time. Even in a scenario in which an invitation is extended at Vilnius, there will be an interim period before membership becomes a reality because of the ratification process. There may also be individual Allies who set conditions or block membership because of bilateral issues. A key consideration is how to secure Ukraine during the interim period until Ukraine becomes a member.

NATO membership – with Article 5 covering all of Ukraine or with geographic limitations – could be preceded by an interim commitment by a coalition of key states to use air power to protect western Ukraine. Such a commitment could be included in a roadmap towards NATO membership. The coalition could, during the interim period before NATO membership, provide partial security guarantees by committing to defending Ukraine with air strikes on Russian military targets inside Ukraine in case of a new land attack west of a Kherson-Dnipro-Kharkiv axis. Such a commitment would, for instance, seek to deter Russia from again trying to attack Kyiv by land.[8]

This commitment would be tantamount to drawing a line in the sand and saying that if Russian troops cross it, Western states will intervene with air power within certain parameters. This would not mean putting western troops on the ground in Ukraine or flying Western aircrafts in Ukrainian airspace, i.e. not exposing Western military assets to Russian retaliation that could trigger Article 5. Nor would it entail striking targets inside Russia. In effect, this would be tantamount to establishing and enforcing a “land force exclusion zone” in western Ukraine.

Such strikes would be carried out from NATO airspace or territory. There would be a clear and communicated limitation on the strikes to reduce the risk of escalation. NATO Article 5 would continue to deter Russia from retaliating against the states that would carry out the strikes.

This commitment would effectively be an extension of the commitment the United States has made to respond to a nuclear attack by Russia in Ukraine. Washington has signalled that it will intervene militarily with conventional weapons, most likely with overwhelming missile strikes on Russian military targets in Ukraine, in case Russia uses tactical nuclear weapons in Ukraine.[9] This commitment could be extended to cover a new land invasion by Russia of Ukraine west of the Kherson-Dnipro-Kharkiv axis.

The commitment to intervene would not – at least to begin with – extend to Russian attacks with missiles, drones, and artillery west of the axis. These strikes are ongoing and likely to continue in the short to medium term. Security commitments may therefore not be effective as a deterrent against Russian air strikes and shelling.

Instead, Western powers should continue to build up Ukraine’s air defence to increase its capacity to intercept Russian missiles and drones. This also includes replenishing stocks of ammunition for air defence. Currently, Ukraine manages to intercept nearly all Russian missiles and drones over Kyiv.[10] Air defence has been less effective in other parts of Ukraine.

Moreover, Western powers could signal that it would accept Ukrainian attacks on military targets on the Russian side of the border, unless Russia stops its air strikes. Hesitation in some Western capitals about Ukraine using Western weapons to attack targets in Russian territory has created a deep military imbalance between Russia and Ukraine.[11] As long as Ukraine has to refrain from cross-border attacks, it will always be at a strategic disadvantage vis-à-vis Russia since the fight will always be on Ukrainian soil. Rectifying this imbalance and using the threat of Ukrainian escalation would seek to deter further Russian airstrikes.

Israel Plus

The commitment to resort to air power should be complemented with a commitment to build up Ukraine’s military capacity over the long term. In parallel to a roadmap for NATO membership, Western powers at Vilnius should commit to long-term military assistance for Ukraine so that it can defend itself against Russian aggression. A state's capacity to resist an armed attack is enshrined in Article 3 of the North Atlantic Treaty. It is also the underlying idea of the Kyiv Security Compact: Ukraine’s international partners should make legally binding, open-ended, and scalable commitment to build up Ukraine’s military industrial production base, to provide Ukraine with modern weapons and ammunition, to share intelligence, to undertake joint training and exercises, and to strengthen Ukraine’s hybrid and cyber defence.[12] This support would also help Ukraine move towards greater interoperability with NATO.

Commitments would take the form of bilateral agreements or memoranda of understanding brought together in a multilateral framework. The involved states would also commit to automatically imposing further sanctions on Russia in case of further aggression. The legally binding and automatic nature of the support is important to entrench effective deterrence. There should be no question about whether parties to the Compact will provide support to Ukraine.

Support for building up a comprehensive and integrated air defence system should also be an integral part of this support. Air defence has proven essential to providing security against Russian missile and drone attacks. While Ukraine is too large geographically to completely protect all its territory against air strikes, key cities and critical infrastructure, such as nuclear power plants, need to have extensive air defence. Over time, Ukraine will need to consolidate the various systems it uses to make sure that they are compatible with each other. Support for air defence should also include providing Ukraine with a fleet of NATO standard fighter jets.

The Kyiv Security Compact to some extent foresees the formalisation of the support provided by Ukraine’s international partners in the Ramstein Format. But it would entail a long-term commitment based on legally binding agreements instead of ad hoc support packages every few months. This commitment could be on a ten-year rolling basis. The binding nature of this support and the long-term perspective foreseen in the Kyiv Security Compact would boost deterrence as it would substantially increase the cost for Russia of an attack. It would also counter the notion held in Moscow that Western unity and support for Ukraine will wane over time.

U.S. commitments to Israel are along similar lines.[13] The United States provides nearly 4 billion dollars’ worth of military aid every year to Israel so that it can maintain its military edge in the region. This support is codified in a memorandum of understanding stretching 10 years. There is also extensive joint development of military technology. But the United States does not send troops when Israel is attacked with missiles from Gaza or southern Lebanon.

A core group of states such as the US, UK, France, Germany, and Poland, could underwrite this binding support for Ukraine. But the EU also has a role to play in building up Ukraine’s military capabilities over time given that it has become one of the main security providers to Ukraine. The EU could, for instance, commit to an initial five-year security package that would include the EU Military Assistance Mission (EUMAM Ukraine) training 250,000 Ukrainian troops, and the European Peace Facility providing 25 billion euros worth of weapons and ammunition over a five-year period. The initiative to procure one million rounds of ammunition for Ukraine could also be increased to five million rounds over five years.

It is important that the Compact is not seen as a substitute or compensation for Ukraine not receiving NATO membership. The two should go hand in hand. Decoupling NATO membership from long-term military assistance would create a situation in which Ukraine becomes a considerable military power but without the institutional restraints that NATO provides. Depending on how the war goes, Ukraine could end up having the capacity to take significant military action against Russia. NATO membership for Ukraine would also ultimately be cheaper for Western allies than an open-ended commitment to fund Ukraine’s military capacity over the long-term.


Ukraine’s Western partners have an opportunity at Vilnius to make a strong commitment to securing Ukraine and embedding it in Western institutions, notably NATO. This would provide greater stability in Europe and predictability in relations with Russia.

NATO Allies should endorse a package at Vilnius that includes a roadmap for Ukraine’s clear and accelerated membership of NATO and, as interim measure, a commitment to security guarantees and an open-ended support to strengthening Ukraine’s military capabilities. Geographic and functional limits on these commitments, notably the threat of air power on Russian military targets in Ukraine in case of a new land attack in western Ukraine, should be an essential part of shaping these guarantees.

Extending Ukraine’s air defence also needs to be a cornerstone of securing Ukraine. Ukraine needs a comprehensive and integrated air defence to neutralise Russia’s ongoing missile and drone attacks. Robust air defence create security conditions necessary for reform, reconstruction, and foreign investment.

Such a comprehensive package could help speed up an end to the war. It would counter Moscow’s strategy of holding out in the hope that Western resolve will collapse over time. Playing the long game could end up shortening the war. It would also strengthen Ukraine’s hand in any future negotiation with Russia. Military bases, troop levels and posture, placement of long-range weapons, military exercises in Ukraine, and so on can be bargaining chips in a future negotiation. This sort of robust backing from the West would strengthen Kyiv’s negotiation position vis-à-vis Moscow.

At Vilnius, the roadmap to membership should also include an upgrade of the NATO-Ukraine Commission to make it a NATO-Ukraine Council with the in-person participation of President Zelensky. This would be an important signal about Ukraine’s future being in NATO and also give Ukraine certain rights such as calling for meetings with Allies. In more ways than one, Vilnius may turn out to be a steppingstone towards a historic decision at the Washington summit in 2024, when NATO will mark 75 years.





[3] Article 42(7) TEU: If a Member State is the victim of armed aggression on its territory, the other Member States shall have towards it an obligation of aid and assistance by all the means in their power, in accordance with Article 51 of the United Nations Charter. This shall not prejudice the specific character of the security and defence policy of certain Member States.
Commitments and cooperation in this area shall be consistent with commitments under the North Atlantic Treaty Organisation, which, for those States which are members of it, remains the foundation of their collective defence and the forum for its implementation.











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Fredrik Wesslau
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Fredrik Wesslau

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Distinguished Policy Fellow

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