No more empty promises: Ukraine must have legally binding security guarantees
By failing to offer Ukraine genuine security guarantees in the past, Europe and the US gave Russia an open invitation to invade. Ahead of a ceasefire, Ukraine must receive effective security guarantees through a clear bilateral or multilateral mutual defence treaty. This would better deter Russian aggression than the current patchwork of political assurances and show that Europe and the US are committed to firmly anchoring Ukraine in the Western security order for the long term.
Guaranteeing long-lasting peace
Binding mutual defence security guarantees are critical to efforts to secure a sustainable, long-term peace and for Ukraine to feel secure ahead of any kind of peace negotiations. They are also crucial for Ukraine to attract the necessary finance for reconstruction and long-term prosperity.
To ensure that Russia will not attempt to rearm and seize more Ukrainian territory in the future, the guarantees must be a robust, legally binding treaty—unlike the 1994 Budapest Memorandum. Back then, the US, UK, and Russia pledged to respect Ukraine’s independence, sovereignty, and territorial integrity in exchange for Ukraine’s accession to the Treaty on the Non-Proliferation of Nuclear Weapons, and Kyiv reducing its conventional weapons arsenal. Viewed as a cornerstone of Ukraine’s security, it proved to be the opposite, failing to provide any legal obligation from the signatories to defend or provide support to Ukraine in case of aggression or a violation of the memorandum.
The 2014/2015 Minsk Agreements also failed to deter Russian aggression. They were poorly implemented, lacked enforcement mechanisms, and interpreted differently by the parties. Russia's role as both mediator and belligerent made the process inherently imbalanced and dishonest, undermining trust and neutrality.
Effective guarantees
While several bilateral security agreements have been signed with Ukraine, they remain largely symbolic, offering little more than political assurances. Ukraine’s security should be anchored within a comprehensive and binding security treaty, modelled on the US framework with Japan, South Korea, and the Philippines. Under those treaties, Washington is legally bound to come to the defence of its allies in the event of an armed attack, and it backs up that commitment with forward-deployed US forces, joint military planning, and regular exercises that keep the deterrent credible.
While Washington has excluded signing such an arrangement with Ukraine—given the existential nature of Russia’s war for European security—Europe should and must. European hesitation has long stemmed from fears of acting independently of Washington. However, US President Donald Trump’s unexpected announcement during his August 18 meeting with European leaders and Ukrainian President Volodymyr Zelenskyy that the US, while opposing Ukraine’s NATO membership, could nonetheless participate in “Article 5–like” security guarantees for Ukraine, marked a potentially significant breakthrough. Trump had previously excluded any US involvement, insisting that Ukraine and its European allies must deal with their security issues alone.
Article 5 of the NATO’s founding treaty does not oblige the allies to defend each other in the event of an attack on one of them. It rather states that each NATO member will assist the Party or Parties so attacked by taking “forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force”. Thus, the plan would provide collective-defence assurances without granting NATO membership. However, the Kremlin may view this as the Alliance giving Russia a de facto veto over Ukraine’s membership, which risks undermining the credibility of the Alliance. Thus, NATO membership should remain on the table.
Europe leads
European countries would be the first line of defence in providing such guarantees. Thanks to Trump demanding that they do the heavy lifting for their own (and Ukraine’s) security after years of relying on Washington, they are now better positioned than previously. Russia’s war has fundamentally changed the way Europe views its own security. Beyond strengthening their own security and defence, European countries and other allies, including Australia and Canada, formed the coalition of the willing (CoW), pledging support for Ukraine. This includes potentially deploying troops on the ground to deter Russia from violating a future ceasefire agreement.
The CoW has taken steps on military, economic and humanitarian aid for Ukraine, along with coordinated sanctions on Russia. However, discussions around deploying a deterrence force into Ukraine to enforce a future ceasefire stalled amid Russian threats of escalation, and Trump’s earlier announcement that the US would not take part. While Ukrainian forces would remain the main line of defence at the front, with European forces acting as a so-called tripwire, Europeans want at least US air power to back them up. Now that Washington has thrown its hat back in the ring, Europe must get serious.
Firming up details
Concrete options must be rapidly agreed, including clearly defining the territorial scope of the guarantees and explicitly covering Ukraine’s internationally recognised borders. The guarantees should include a policy of non-recognition concerning occupied Ukrainian territories, and encompass not only military support but also diplomatic and economic measures. By doing so, these treaties would ensure a comprehensive framework for Ukraine’s security, addressing the full spectrum of threats and challenges, and reinforcing Ukraine’s sovereignty through a coordinated, multi-dimensional approach. They would also complement and reinforce Ukraine’s effective and robust homegrown deterrence, which is arguably Ukraine’s best security guarantee.
The security agreements Ukraine has signed in recent years are misleading in name, offering little real protection in its fight against Russian aggression. Yet there is no need to reinvent the wheel, as these agreements already contain many of the elements that could form the foundation of a genuine mutual defence treaty: strategic partnership, developing the security and defence sector, building homegrown deterrents, etc. The only part that is currently missing is a mutual defence element backed by strong political commitments, and a clear implementation plan. The CoW serves as the most effective venue to refine this framework and reframe these agreements into a binding multilateral mutual defence treaty for Ukraine.
US Secretary of State, Marco Rubio, is heading a working group of national security advisers and NATO representatives to draft a security guarantees plan. It must define how the CoW will be able to respond to attacks in the sky, at sea and on land, including using drones and artificial intelligence and encompass a military presence and armaments, air defence, and ceasefire enforcement. Several discussions, including a virtual meeting with 32 allied military leaders, led by US General Alexus Grynkewich, NATO’s Supreme Allied Commander, have been held. The result will depend on the text negotiated and the political will to implement it.
A robust US backstop to carry out intelligence, logistics support, and potentially significant air support is possible and crucial. This could include providing more air defence systems to Ukraine and enforcing a no-fly zone with US airpower together with the Europeans. The US may also lead command and control, which can be done from a distance.
Keeping Trump onboard
Trump’s unpredictability works against Europe. He may change his mind, or Russian President Vladmir Putin may change it for him. Trump’s change in narrative has not gone unnoticed by the Kremlin, which immediately reiterated old demands about no role for NATO forces in Ukraine.
Putin believes that he can bend Trump to his will. The result of the Alaska Summit showed that certain Russian narratives can get through; for example, the joint decision to bypass a ceasefire and move directly toward a peace deal via a bilateral meeting between Putin and Zelenskyy. Putin is slow rolling the process. He is not interested in meeting with Zelenskyy or in ending the war until he receives the concessions that he has long demanded.
Ongoing internal strategic and political divides in Washington are also challenging. US Undersecretary for Defense Elbridge Colby, and Secretary of Defense Pete Hegseth prioritise strategic restraint and have repeatedly blocked Ukraine from using US long-range Army Tactical Missile Systems (ATACMS) to strike targets inside Russia. Trump has been unable to prevent this blockage. While Ukraine’s recently developed Flamingo long range missile can fill this gap, such steps by Washington further encourage Putin.
Still, following Trump’s meetings with Zelenskyy and European leaders, Trump seems to have returned to the idea of a ceasefire-first approach. However, Europe will need to continue to reiterate why this is crucial, even if this means calling the US President every day. They should also launch a focussed advocacy campaign, highlighting Ukraine’s battlefield successes as well as flagging the importance of Ukraine’s EU accession for Transatlantic security
Trump gravitates toward winners and wants to be seen alongside them. Recognising Ukraine’s battlefield achievements and broader resilience is essential, along with continuing to flag Russia’s attacks on critical infrastructure, civilians, and the kidnapping of Ukrainian children—which led to first lady Melania Trump writing to Putin. Trump was furious about Russia’s attack on a US company based in Ukraine, leading to renewed threats to impose sanctions on Russia if there is no progress toward a peaceful settlement. Still, based on Trump’s failure to follow through on previous threats, Putin will not be worried. Only decisive and forceful action will stop him. Trump has the tools to do this and should—only then will Putin take him seriously.
Europe thus finds itself with two unlikely allies: Rubio, who remembers the disastrous Minsk process and understands Russia’s long game, and the US Congress. The Sanctions Bill, which has already garnered overwhelming bipartisan support and near-unanimous Senate co-sponsorship, is a powerful lever. European lawmakers must advocate to their US counterparts to go ahead with the legislation by moving it to the floor, even if it could frustrate Trump, who has been delaying the sanctions rollout despite threatening them. However, it might also compel him to rethink his approach to Putin. Ironically, if implemented, the sanctions could end up strengthening Trump’s hand internationally—even positioning him for his much-desired Nobel Peace Prize.
Going it alone
When America hesitates, Europe holds its breath—and Ukraine bleeds. This time if the worst-case scenario unfolds, and Trump does pull back, Europe cannot hesitate. Europe and other allies must be ready to go it alone; in fact, they should already be preparing for this very likely outcome now. Burying heads in the sand is not a solution.
Amanda Paul, Deputy Head of the Europe in the World Programme and Senior Policy Analyst
Lev Zinchenko is a former Programme Assistant in the Europe in the World Programme at the EPC, and Advocacy Programme Coordinator at Razon for Ukraine.
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