“Security Guarantees” for Ukraine: Breathing Life into a Buzzword
By: Paula C. Kates, Sindija Beta & Dr. Paul R. Williams
The purpose of this blog is to explain what is meant by the now frequently used term “security guarantees” in the context of Russia’s war of aggression against Ukraine.
Following President Donald Trump’s meeting with Vladimir Putin in Alaska on August 15, 2025, and his subsequent meeting with President Volodymyr Zelenskyy and several European leaders in Washington, D.C., on August 18, 2025, a renewed focus has emerged on the question of “security guarantees” for Ukraine.
The phrase “security guarantees” is an often used buzzword, which few diplomats, commentators and even experts seem to understand.
This blog explores the multiple dimensions of the term “security guarantees,” including: What does the term “security guarantees” traditionally mean? What constitutes an Article 5-like guarantee? Which states or organizations might implement such guarantees? Does an Article 5-like guarantee require the deployment of combat troops on the ground in Ukraine? What options exist for configuring combat forces—or other types of security forces—on Ukrainian territory? How might these forces operate in the absence of an Article 5-like commitment? And finally, what binding obligations or discretionary measures might apply to—or be available to—the United States?”
What does the term “security guarantees” traditionally mean?
There is no universally accepted definition of the term “security guarantees.” Some argue that a true “guarantee” of security is impossible and prefer the term “security commitment” to reflect the reality that no state can fully ensure the security of another. Nonetheless, in common discourse, security guarantees are generally understood as commitments to safeguard and maintain the status and territorial integrity of a specific state or entity against external aggression. These guarantees may be extended by individual states, groups of states, or international organizations.
For instance, the Mutual Defense Treaty Between the United States and the Republic of Korea of 1953, commits the United States to come to South Korea’s defense in the event of external aggression. Since its signing, the United States has provided extensive defense support and has maintained a military presence in South Korea as a deterrent. Notably, the Treaty also extended the U.S. “nuclear umbrella” to the Republic of Korea, meaning that the deterrent effect of U.S. nuclear weapons applies not only to threats against the United States itself but also to those targeting South Korea.
An example of a multilateral security guarantee is the European Union member states’ commitment enshrined in Article 42(7) of the Treaty on European Union. Under the Article, member states are obliged to provide “aid and assistance by all the means in their power” to any other member state that is the victim of armed aggression on its territory. What distinguishes this clause from that of the United States and Korea Agreement is that, as the European Union is not a military institution, “all the means in their power” does not necessarily mean using armed force and may instead refer to non-military measures such as sanctions, economic assistance, diplomatic pressure, cyber defense support, or logistical coordination.
What constitutes an Article 5-like guarantee?
The notion of an Article 5-like guarantee has its origins in Article 5 of the North Atlantic Treaty. Article 5 provides that “an armed attack against one or more [member states] in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defense … will assist the Party or Parties so attacked.” Put simply, Article 5 legally binds all NATO members to come to the aid of any single NATO member state that is attacked.
Article-5 like guarantees for Ukraine were proposed during the Istanbul talks of March 2022 where it was suggested that, in lieu of full NATO membership, a coalition of willing states could provide a collective security guarantee akin to that provided by Article 5. Russia counterproposed with the insistence that it be one of the guarantor states with a veto power over any support that may be provided should Ukraine again become a victim of armed aggression.
In March of 2025, Italian Prime Minister Giorgia Meloni floated a similar proposal for Article 5-like guarantees. Contemporaneous commentary indicated that the Prime Minister intended for NATO and its member states to provide the collective security guarantee; but since Ukraine would not be a member state it could not be termed an Article 5 guarantee, and thus must be called an Article 5-like guarantee. At the time, Prime Minister Meloni reportedly envisioned that no NATO member state would necessarily need to station combat troops in Ukraine, as such an approach would be more acceptable to Russia.
Following the recent summit between European leaders and President Trump in Washington, new details emerged regarding Italy’s evolving proposal on security guarantees. According to reports, the Italian government circulated a more formal draft to summit participants, outlining a collective assistance mechanism as an alternative to NATO membership. The plan would commit nations with bilateral agreements with Ukraine to swiftly coordinate a response in the event of an attack, potentially within 24 hours, though some countries have suggested timelines ranging from 12 to 72 hours.
Proposed measures include rapid and sustained defensive support for Kyiv, economic aid, military reinforcement, and sanctions against Russia. While it remains unclear whether European troops would be deployed on Ukrainian soil, sources indicate that the framework could mirror the 2024 Rome-Kyiv bilateral pact. The reaction force might involve all NATO members, a subset, or even interested non-members like Japan and Australia. Crucially, any immediate response would rely on NATO’s existing infrastructure. Should Moscow launch an attack against Ukraine, a consultative process among guarantors would determine a proportionate—military or economic—reaction.
While Italian Prime Minister Giorgia Meloni has notably distanced herself from the Coalition of the Willing initiative, particularly regarding proposals that involve deploying European troops to Ukraine, recently Italian Minister of Defense, Crosetto, clarified that this proposal is not mutually exclusive with the “Coalition of the Willing” concept, and both approaches could coexist.
What kinetic or other action could be taken under an Article 5-like guarantee?
At its core, an Article 5-like guarantee implies the potential for a military response to defend Ukraine in the event of renewed aggression. This could involve direct deployment of combat forces or the use of military capabilities to repel an attack. However, recent discussions—particularly among European states—have signaled growing interest in a broader spectrum of responses that fall short of direct military engagement.
One such alternative involves robust and sustained financial and arms commitments that enable Ukraine to maintain a level of military capability sufficient to deter future aggression on its own. This approach would avoid the need to deploy guarantor states’ militaries, but would require a significant and ongoing flow of weapons, ammunition, and funding. As war fatigue sets in across Europe and political support in the United States continues to erode, the prospects for maintaining such high levels of assistance are increasingly uncertain.
Moreover, a security guarantee structured solely around arms and financing—without the credible threat of direct military response—would only marginally exceed the support already provided to Ukraine by its allies to date. As a result, the credibility and deterrent power of such a guarantee may be limited unless paired with explicit political commitments or the credible presence of forward-deployed forces.
Which states or organizations might implement such guarantees?
More recently the Article 5-like guarantee has evolved from a guarantee by NATO to a guarantee by a so-called "Coalition of the Willing"willing to participate in an ad hoc security arrangement. France and the United Kingdom have indicated a willingness to participate in such a coalition and to possibly deploy combat troops to Ukraine, though to limited geographic areas. Germany and Poland have also indicated a willingness to provide these Article 5-like guarantees as part of a coalition, but would not station combat troops in Ukraine. Other states, including several European states, Japan, New Zealand, and Australia, have expressed interest in the Coalition of the Willing but have not provided a definite position on what could be their involvement.
Notably, after the European meeting with President Trump on August 18, 2025 NATO Secretary General Mark Rutte seemed to resurrect the idea that the Article 5-like guarantees would be provided by NATO.
President Trump has indicated that he, and even President Putin, are open to Article 5-like guarantees, though it does not appear that either one of them envision the United States itself providing such a guarantee.
Importantly, without a commitment from the United States for significant American involvement, any attempt at “Article-5 like” security guarantees may fall far short of what is guaranteed by Article 5 given the limited military infrastructure of the other NATO member states.
While there has been some discussion that nonaligned states could play a role in providing security guarantees or act as a peacekeeping force either under a United Nations mandate or another mechanism, to date, there has been little development and interest in turning the discussion into practical measures. When it comes to mandating such a force by the United Nations, Russia’s role as a permanent member state of the UN Security Council makes the debate unfeasible due to well-founded concerns over Russia’s interests in manipulating the mandate of a UN peacekeeping force and the power to subsequently withdraw the force prematurely to suit its political interests.
Does an Article 5-like guarantee require the deployment of combat troops on the ground in Ukraine?
Under the Italian proposal, it would not be necessary to deploy troops in order to guarantee Ukraine’s security. The concept relies instead on the deterrent effect of a credible threat—the potential use of force by NATO or a coalition of the willing—as sufficient to prevent future Russian aggression.
More recent proposals, however, envision a stronger form of deterrence that combines an Article 5-like guarantee with the deployment of some kind of military force away from the frontlines as additional support to the Ukrainian military, and possibly U.S. air support. The specific configuration of such forces is discussed in greater detail below.
What options exist for configuring combat forces—or other types of security forces—on Ukrainian territory?
British officials have indicated readiness to place British troops in Ukraine, as have Belgium, Lithuania, and Estonia. On the other end of the spectrum are Poland, Germany, and Hungary, all of which have firmly declined the option of placing their troops in Ukraine. The United States has also dismissed the deployment of American troops inside Ukraine.
Troops that would be deployed could be done so in multiple configurations.
Enforcement force: An initial, but now seldom discussed, option involves deploying a fully militarized peacekeeping force along the line of control between Russia and Ukraine. This force would be tasked with monitoring compliance, maintaining separation, and potentially responding to violations, much like traditional enforcement missions.
Reassurance force: A more frequently discussed configuration envisions forces providing air cover over western Ukraine, conducting demining operations in the Black Sea, and protecting key ports and airfields. These efforts would be paired with ongoing training and advisory support to the Ukrainian military, enhancing both operational readiness and public confidence in Ukraine’s defense posture.
Deterrent or “Tripwire” force: Under this model, a smaller number of international troops would be positioned in strategically significant areas to serve as a deterrent “tripwire.” The logic is that any attack resulting in non-Ukrainian casualties could trigger a military or other forceful response from coalition member states—thereby raising the political and operational cost of aggression.
U.S. Role and Requirements: European states have made clear that both the reassurance and tripwire models would require two key forms of U.S. support: (1) logistical, lift, intelligence, and munitions assistance; and (2) “over-the-horizon” combat support. Notably, President Trump has yet to clearly articulate the role he envisions for the United States in any such arrangements, although he has hinted at a potential willingness to provide air support.
Other lighter footprint options occasionally discussed include a monitoring force and/or a training force. A monitoring force would consist of a small number of on-the-ground personnel tasked with observing and reporting potential violations of a peace agreement. In theory, such a force could play a critical role in verifying substantial breaches of the agreement and, in doing so, could trigger a military or other form of response from coalition of the willing member states.
The lightest form of on-the-ground involvement would consist of a limited number of personnel tasked with providing ongoing training to the Ukrainian military and assisting in the strengthening of Ukraine’s defense systems. This model could share features with a tripwire force by effectively embedding non-Ukrainian military staff within Ukrainian units—creating a scenario in which any attack on Ukrainian forces could endanger foreign personnel. Such a configuration, while limited in scope, could still serve as a meaningful deterrent by raising the stakes of Russian aggression.
How might these forces operate in the absence of an Article 5-like commitment?
Importantly, it is not necessary to establish an explicit Article 5-like security guarantee in order to deploy troops to Ukraine from member states of a coalition of the willing. In particular, forces deployed in roles such as tripwire, monitoring, or training missions could still serve a significant deterrent function. If these personnel were to be targeted by Russia, the political and strategic consequences would likely be severe, potentially triggering a strong collective response—even absent a formal mutual defense commitment. The mere presence of such troops, especially from NATO or EU member states, may thus serve as a powerful signal of resolve and solidarity with Ukraine.
What binding obligations or discretionary measures might apply to—or be available to—the United States?
Some commentators have suggested that a coalition of the willing—composed in part of NATO member states—could serve as a backdoor mechanism for securing U.S. security guarantees. The logic behind this view is that if a NATO member state, acting within such a coalition, undertakes military action in defense of Ukraine and is subsequently attacked by Russia, this could trigger Article 5 of the NATO Treaty, obligating the United States and other NATO members to respond. However, it remains unclear whether the United States views such a scenario in the same light, or whether it would interpret an attack on a coalition-based deployment as meeting the threshold for collective defense under NATO’s legal framework.
Security Guarantees - the Russian perspective
While Western states may be debating how to make sure the security guarantees truly prevent the resumption of a renewed aggression some years after signing the peace agreement, the Russian perspective on the conversation is noticeably different. After the August 2025 meetings, reports celebrated the fact that Putin had allegedly agreed to security guarantees for Russia. What was missing from the celebration was that, for Russia, security guarantees mean no NATO or European troops in Ukraine and a veto for Russia on any assistance that could be provided to Ukraine in the event of a new war. This, as noted above, is what already created an impasse at Istanbul in 2022.
Why are security guarantees so important?
Security guarantees are crucial to any peace deal because of Russia’s history of violating ceasefires and peace agreements. To take one example, during the 2008 Russo-Georgia War Russia invaded the Georgian regions of Abkhazia and South Ossetia. A ceasefire was brokered, but immediately broken by Russia when it refused to withdraw its troops from the Georgian regions. Ukraine has itself faced numerous broken agreements with Russia. In 1994, Ukraine entered into the Budapest Memorandum in which, among other things, Russia committed to recognizing Ukraine’s independence, sovereignty, and borders—and to guard against any foreign intervention. This guarantee failed. Similarly, in the wake of Russia’s 2014 aggression against Ukraine it entered into the Minsk Protocols, which Russia also violated. Based on this history, Ukraine is adamant that serious security guarantees are necessary in order for there to be any substance to a peace agreement with Russia.
Conclusion
The evolving discourse around “security guarantees” for Ukraine reflects both the urgency of Ukraine’s need for credible protection and the complexity of delivering such protection in the current geopolitical environment. As the concept moves from rhetorical aspiration to operational planning, the range of proposed guarantees—from formal Article 5-like commitments to more flexible coalitions of the willing, and from fully deployed combat forces to lighter tripwire and training missions—demonstrates the varied levels of risk, resolve, and resources that different states are willing to assume.
Ultimately, the credibility of any security guarantee for Ukraine will depend less on the terminology used and more on the political will behind it, the clarity of its implementation mechanisms, and the strategic signals it sends to both allies and adversaries. Whether through direct deployment, sustained arms support, or embedded international personnel, the international community must now translate the concept of “security guarantees” into practical and enduring measures that both deter further aggression and support Ukraine’s long-term sovereignty and stability.