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Post-War Security for Ukraine: Eventually the Fighting Will End. What Then?

March 02, 2023
Stefano Stefanini

One year on, no end to the war in Ukraine is in sight. The conflict is escalating. But at some point, the fighting will come to a halt, and it is not too early to think about what should come next.

Since both a Ukraine-Russia peace treaty and a comprehensive European security framework will only become possible in the long term, even after cessation of active hostilities, it will be necessary to fill the security vacuum in the short-to-medium term. The most realistic option, in my view, would be for the West to provide Ukraine with a comprehensive “security safety blanket,” including bespoke, fool-proof international security guarantees—specifically, by an ad hoc group of countries—while pragmatically engaging Russia in negotiations on arms control and limitations, inclusive of conventional weapons and forces, and on establishing a safety net of confidence-building-measures across the Euro-Atlantic space.

Securing Ukraine will be the most pressing task. But international guarantees to that effect will be influenced by the wider state of European security. First and foremost, they will have to spell out clear terms and mechanisms for military support to Kyiv in case of further Russian aggression. At the same time, Ukraine policy cannot be disconnected from Russia policy, with the latter aimed at lowering the risk of military confrontation and at resuming talks on arms control and limitations.

End-of-War Scenarios

Wars determine post-wars. As the outcome of the Russia-Ukraine war is still uncertain, any prediction of how it will end is at best an extrapolation from present trends and experts’ estimates—which have been repeatedly off the mark in the last 12 months. What is clear is that Ukraine and Russia appear locked in a conflict that neither is likely to win decisively and that a definitive peace settlement is hardly conceivable with Vladimir Putin in power. This suggests that post-war planning should begin by focusing on a frozen-conflict scenario preceding any possible peace settlement.

A frozen state of the current war would mean that fighting ends with a Korea-like ceasefire, or armistice at best, but without a peace treaty. This kind of war ending is not uncommon. In this case it would have four major consequences:

  1. It would bring a pause in the fighting but not peace between Ukraine and Russia.
  2. Ukraine would remain vulnerable to Russia’s aggression.
  3. Russia would remain an oversized regional great power and a nuclear superpower with unfulfilled nationalistic/imperial ambitions.
  4. Absent a peace treaty, both countries will maintain claims on territory under the other side’s control—without international recognition in Russia’s case.

This frozen conflict scenario could potentially play out in the near-to-medium term when, for a combination of military and political reasons, both sides reach the exhaustion threshold and are forced to temporarily give up their respective goals. That would not imply readiness to negotiate a settlement. Putin would not backtrack on the annexations he has legally enshrined—only “pause” from implementing them on the part of Ukrainian territory not under Russia’s control at cease-fire time. Anything short of that would strike Putin as jeopardizing his regime, in my view. Meanwhile, if the annexations are unnegotiable, Ukraine would have zero incentive to negotiate anything at all.

With change of mind in the Kremlin highly implausible, a peace treaty will have to wait until a post-Putin regime.

Succession in Moscow must come from within, originated either by domestic political dynamics or by time and human mortality. Ukraine's defensive war, fought by Ukrainians and supported by Western allies, does not aim at regime change in Russia. Therefore, peace and stability are an aspiration for the long term, when circumstances permit, and most likely a post-Putin scenario.

The intermediate period will be fraught with risk. And it could be very long.  

Post-War Challenges: Securing Ukraine and Dealing With Russia

The frozen-conflict scenario will leave full potential for resumption of war. Since cessation of hostilities will simply mean “live to fight another day,” it will be up to the international community to prevent a new Russia-Ukraine war from breaking out again.

The 2014 crisis, which led to Russia's annexation of Crimea and to the Russia-supported violent separatism in the Donbas, was primarily dealt with by the West as a bilateral Russia-Ukraine dispute. Twice Moscow and Kyiv were brought to the negotiating table in Minsk with Germany and France acting as mediators; twice the Minsk agreements proved ineffective and non-complied with. Low-level warfare continued unabated despite a limited OSCE presence on the ground.

To avoid repetition, the Russia-Ukraine war must be recognized as a European security breakdown. While only the Ukrainians can negotiate directly with Russia the terms of cease-fire, and eventually of a future peace treaty, the international community—where the heavy lifting will fall to the West (i.e., the U.S., NATO and the EU)—will face two main challenges guaranteeing Ukraine’s security against future Russian aggression and engaging Russia in rebuilding strategic stability in Europe.

Neither challenge is new. The writing has been on the wall since 2014, if not earlier. The war is the result of failure to meet them: Ukraine was not secured; Russia was not engaged. The Russian aggression of February 2022 has dramatically degraded Ukrainian and European security. This degradation will outlast the end of hostilities, making it imperative that this time both challenges be met.  

Guaranteeing Ukraine’s Security: The Options

Recent history has seen a flaccid international attempt to assure Ukraine's security: The 1994 Budapest Memorandum aimed—and managed—to “denuclearize” Ukraine (as well as Belarus and Kazakhstan) by transferring to Russia the Soviet nuclear weapons located on Ukrainian territory; in exchange, the signatories—Russia, the U.S. and the United Kingdom—gave Ukraine a watered-down assurance of not threatening or using military force or economic coercion. This was done by reaffirming previous international commitments such as the U.N. Charter and the Helsinki Final Act. Absent from the document was any specific mechanism for redress or commitment to assist Ukraine in case of violation.

When in 2014 and in 2022 one of the signatories, Russia, used military force against Ukraine and violated its territorial integrity, Kyiv found itself without an effective international safety net. It faced aggression by itself. Therefore, any future international guarantees need to go beyond the Budapest Memorandum. Specifically, they must include provisions for and mechanisms of military support to Ukraine in case of aggression by Russia.

Options for international security guarantees would fall into three broad categories:

  1. Collective security through structured alliances, primarily by NATO and, to a lesser degree of effectiveness, by the European Union;
  2. Neutrality with security guarantees by an ad hoc group of countries;
  3. Neutrality with security guarantees by military deterrence. (Barring possession of nuclear weapons, military deterrence would have to rely on strong national conventional capabilities that could be enhanced by bilateral defensive agreements/cooperation with individual friendly countries.)

Any of the above could be reinforced by temporarily or permanently stationing troops and assets in Ukraine.

Short of full NATO membership for Ukraine, which would rule out neutrality, there is room for combining elements from different options, especially 2 and 3.

Finally, Ukraine’s post-war security cannot be dealt with in the abstract. How hostilities end will matter to any solution. If Ukraine is in a position of strength on the ground, it will be in a position of strength in negotiations. Hence, the more the military balance has tilted in its favor before the war ends, the better chances of gaining security after. To this end continuing Western military assistance is crucial not only in an immediate sense but in a post-war perspective. 

Pros and Cons of Each Option

Starting with Option 1, NATO membership is by far the strongest security guarantee available to Ukraine. Not surprisingly, Kyiv has been seeking it, on and off, since at least 2008. In a cease-fire scenario it would run up against three hurdles: First, could NATO, a defensive alliance, accept as a full-fledged member a country technically still at war? Second, would there be consensus on Ukrainian membership, which has eluded the alliance since the 2008 Bucharest summit? And, third, would it prevent Russia from agreeing to a cease-fire? All these make the NATO option premature, but it needs to remain on the table, at least as a bargaining chip in a future peace settlement.

Second-best under Option 1 is EU membership for Ukraine. It has one advantage over NATO: It is compatible with neutrality—witness Austria and Ireland. But time is a factor: Under normal circumstances the process of joining the bloc takes a minimum of five years. Besides, it offers a lower, and untested, level of collective defense than NATO: “an obligation [from the other member states] of aid and assistance by all the means in their power” in case of “armed aggression on the territory” of a member state.1 And in terms of military capabilities the EU is no match for NATO. Yet EU membership would lock Ukraine in a powerful bloc of countries that are de facto obligated to protect each other if attacked.

On the other end of the spectrum, a militarily strong Ukraine (Option 3) would be both necessary and insufficient. Necessary because of Russia’s track record: Ukraine survived the Russian onslaught thanks to its military performance. Insufficient because Russia has the “mass” and resources advantage: In a long-run bilateral arms race, Ukraine would always find itself behind.

Thus, international military support must fill the gap.

Russia needs to be put on notice that another offensive war against Ukraine would be a war against a larger-than-Ukraine military line-up, ideally a pre-established coalition (Option 2). That would require a substantial group of countries willing to sign on to guaranteeing Ukrainian security. To be credible it would have to include the United States and a strong European NATO/EU core, with neighboring Poland and Romania in it for geography and logistics, possibly also Turkey. The group would not be an alliance, nor would Ukraine be part of it. It would provide a sum of individual commitments to Ukraine’s security and defense. They would kick in in case of violations of the territorial post-cease-fire status quo, without prejudice to internationally recognized borders. Since the commitments would have been made well in advance of the violation, military intervention by signatory countries in support of Ukraine would be in compliance with an international obligation and could not be constructed as “offensive” by Russia.

Compared to NATO membership, such guarantees would amount to last-resort counter-insurance—an “Article 5 lite.” The downside is that it would not have the solidity of NATO collective defense. In case of Russian aggression, signatories would still have to decide nationally whether to follow through with their commitments. In this context, factors like stationing troops in Ukraine, even as a “trip-wire” presence (NATO Enhanced Forward Presence), would come into play as reinforcement of the legal guarantees.  

Landing Zone: The Best Option

All things considered, international guarantees by an ad hoc group of countries (Option 2) appear to be the most practical and feasible solution. However, they will have to be sustained by a comprehensive “Ukraine security safety blanket,” including:

  • Continuing partnership with NATO, through the NATO-Ukraine Council (NUC); 
  • Fast-track EU membership for Ukraine;
  • Maintaining strong national defense capabilities with continuing Western assistance and training; 
  • Maintaining sanctions on Russia but using them flexibly as “carrots and sticks” contingent on Russia’s behavior (while there might be some easing of sanctions in response to progress, the full lifting of sanctions would depend on the recognition of Ukraine’s sovereignty in a definitive peace settlement);
  • Negotiating deconfliction arrangements on both sides of the cease-fire demarcation line, such as withdrawal of heavy artillery, demilitarized buffer zones, etc. (these would have to be negotiated primarily between Ukraine and Russia and would dovetail with the other challenge—engaging Russia on European strategic stability at large).   

Putin’s Russia: To Deal or Not to Deal?

Dealing with Russia on European security should not be contingent on regimes; it is a must no matter what regime holds power in Moscow. We can’t do business with Vladimir Putin.  But we need to remain in business with Russia on the matter of security.

Assuming Russia will be willing to engage—which cannot be taken for granted—the process will be rife with hindrances. Initially, the only realistic goal could be to recreate a relatively stable and predictable security environment on the ground. Resumption of the U.S.-NATO-Russia dialogue should first aim at low-hanging fruit of reciprocal interest: restoring military-to-military communication, establishing confidence building measures, toning down military posture at borders, downsizing military exercises. A second, parallel task would be to restart negotiations on arms control and limitations, which remain a fundamental building block of any future architecture of European security. Despite Russia’s “suspension” of the New START Treaty, the effort to re-engage Moscow on arms control and limitation must be made as soon as circumstances permit. Most likely it will have to wait for the end of hostilities in Ukraine. It should leverage reciprocal interest not to kick off a new arms race, which would become the inescapable alternative. Whatever Putin’s rationale in deciding to withdraw from New START, Russia’s perception of its own security would be enhanced by the former and aggravated by the latter.

Together these undertakings would also lower threat perception, be it a clear and present threat—e.g., from Russia against Ukraine—or an imaginary but consequential one, e.g., from NATO or other powers against Russia. With whom to negotiate but with adversaries? Including Vladimir Putin, but with a caveat: “don’t trust, do verify.”

The Endgame

Henry Kissinger has made a compelling case for Russia’s “contributions to the global equilibrium and to the balance of power for over half a millennium.” However, it must be recognized that at present Russia is the destabilizing factor in European security. As U.N. Secretary General Antonio Guterres remarked “there are Russian troops in Ukraine, but there are no Ukrainian troops in Russia.” Thus, if the strategic goal is to allow Russia to return to a constructive international role, at present European security needs to be stabilized without relying on Russia to contribute to it. While waiting for Russia to return to being a player instead of a spoiler, Ukraine needs to be secured. Eventually, the post-war scenario could move from frozen conflict to peace settlement. In the interval Ukraine will need the “security safety blanket,” including actionable international guarantees.

Such a security blanket would provide Ukraine a protective political and military shield during the transition from cease-fire to peace, no matter how long the transition takes. It need not be a straitjacket. It will combine elements of a transitional and a permanent nature: International guarantees would be temporary, lasting only as long as the counter-insurance they provide is necessary; EU membership would be a permanent strategic goal, outlasting the transition. Sanctions will remain an eminently adaptable and elastic tool. Ukraine’s status, whether neutrality or NATO membership, would be decided after the peace settlement. The entire package will require creativity in design and flexibility in implementation. This is what after-war diplomacy will be about.


  1. Article 42.7 of the Lisbon Treaty.

Stefano Stefanini

Stefano Stefanini is a former Italian ambassador who has served in Perth, the U.N. (New York), Moscow and Washington. He is a former Permanent Representative at NATO and Diplomatic Advisor to Italian President Giorgio Napolitano. He is a nonresident senior fellow with the Atlantic Council, on the executive board of the European Leadership Network and a columnist and consultant.

The opinions expressed herein are solely those of the author. Photo shared under a Pixabay license.