Overview
Despite frantic US mediation, Russia and Ukraine war aims remain deeply at odds and expectations of bilaterals or trilaterals are premature. However, a significant step comes from the US, which has publicly suggested it would support a European-led security guarantee to Ukraine. Detailing the extent of US support will be essential to deciphering a new European security architecture. At its most ambitious, a coalition of the willing could seek to station several brigades in Ukraine to act as a tripwire to deter Russian threats. If more limited, this coalition could pursue a train and equip function with boots on the ground. Regardless of the specific model, the prospect of a weak security guarantee invites Moscow’s hybrid warfare and undermine Ukraine’s reconstruction, military reconstitution, and investments in the minerals sector.
Ukraine and Russia: Where the Players Stand
As it stands, the prospects for peace between Russia and Ukraine are narrow. A whirlwind of high-stakes US-based mediation in mid-August, in a sort of reverse shuttle diplomacy, reiterated diametrically opposed war aims: Ukraine seeks to recapture all territory occupied by Russia, while Russia wants to capture all of Donbass—a strategically vital region due to its industrial capacity, fortified cities, and high elevation—in addition to preventing Ukraine’s Westward drift toward NATO. With neither side able to break the entrenched frontline, there is no foreseeable military conclusion that can moderate these objectives. There was movement in offering security guarantees to a sovereign Ukraine as part of a peace settlement, but even this remains ambiguous and rife with contradicting interpretations. Nonetheless, if peace is to be struck in the current round of diplomatic momentum, substantiating this point will be the core of a post-ceasefire settlement and the European security architecture.
The only true security guarantee is the ability to defend oneself indefinitely, which is Ukraine’s goal behind any final model. Ukraine is concerned with Western wobbliness; as part of the 1994 Budapest Memorandum, the country gave up nuclear weapons inherited by the USSR in exchange for security assurances, a similar pledge that ended up being no more valuable than the paper it was inked on. Giving up four-fifths of its Black Sea Fleet to Russia in exchange for similar pledges did nothing to prevent the illegal annexation of Crimea in 2014. To avoid repeating past mistakes, Ukraine desires something substantive, ideally NATO membership or an “Article 5-like” collective security commitment, even if the covered area (NATO’s Article 6) only extends to controlled territory. While NATO membership may have to be reserved as a long-term goal, an intermediate phase—with a heavy presence of Western troops and an emphasis on training to achieve NATO interoperability—is more akin to Ukraine’s immediate vision.
Russia maintains maximalist goals to address the “root causes” of the war: geopolitical neutrality, no NATO membership, and protecting the status of Russian ethnics—likely a euphemism to create a vassal government, given the failure of the 2014 and 2015 Minsk Agreements to enact a ceasefire based on decentralization and minority rights. Russia’s obsession with Ukraine, as opposed to the Balts or Finland, seems driven in part by irredentist nationalist politics—one that considers eastern Slavs as a “natural” political community and a separate Ukrainian identity as an artificial creation—but also in part an opportunistic belief that Ukraine will capitulate. In sum, Russia views Ukraine as its entitled sphere of influence and a legacy for political elites to recoup lost glory after the fall of the USSR. Aligning with this perspective, Russia’s envisioned security guarantees must include the “equal” participation of both Russia and China as great powers, in addition to the US, UK, and France—basically, a UN Security Council-like guarantee with Russian veto power. Of course, Ukraine sees this demand as the prologue to another full-scale invasion.
This impasse will spell trouble for a peace settlement and render the diplomatic drama largely trivial. The real action is not currently between Ukraine and Russia, but rather between Ukraine and the Western powers. Ukraine understands that its diplomatic capital is best spent on aligning visions of a postwar security architecture with European allies, ideally with US backing, to control the terms of a future negotiation and potentially provoke pressure on Russia—seen as the obstructing power—into negotiations or military defeat. A security guarantee can provide clarity on Ukraine’s defensive needs and lock-in military assistance, regardless of Russian objections.
The Europeans Reflect Upon a New Security Architecture
The US signaled openness to supporting a security guarantee after the August 18 White House summit, but European powers understand that they will shoulder the “lion’s share” of the burden. Without formal NATO membership, a security guarantee remains nebulous but will include some essential ingredients—rebuilding Ukraine’s military, strengthening both the EU and Ukraine defense industrial base, and potentially stationing troops, likely in a training capacity but most ambitiously as a “tripwire” force to raise the risks of a Russian incursion.
Consolidating an entente of European powers, while hardly an impossibility, will be harder said than done. This is not least because Europeans face the dilemma of trading Warsaw or Paris capitals for Kyiv (which every surging populist extremist party in Europe will explicitly reject, to Moscow’s glee), but because competing foreign policy visions are shaped by the continent’s constraints. First, the US is undertaking a force posture review that could initiate the drawdown of its stationed troops; to fully replace the American presence (the most extreme scenario), Europe collectively would need to develop an expeditionary-ready force of up to 300,000, a tall order considering powerhouses like Germany are struggling to field even one 5,000-strong brigade in Lithuania under the NATO battlegroup concept. Second, Europe must develop its own defense industrial base to produce at scale in parity with Russia. Here, a partnership makes sense with Ukraine, whose twenty-fold increase in military procurement spending from 2021-2023 has sparked an economy of scale unrivaled in Europe. About 80% of Ukraine’s defense needs now come from domestic companies, which are prime partners for joint ventures with European armament firms. Nonetheless, EU nations will need to expand their own buying power, such as by expanding the €150 billion SAFE loans program or deficit spending, to produce at a comparable volume—which is hardly inevitable.
Only after reflecting on manpower and defense industrial constraints can the Europeans consider joining a “coalition of the willing” to station troops in Ukraine. The UK and France, two European powers with ample expeditionary experience, originally led the charge for a “reassurance force” of up to 30,000 troops to supplement Ukrainian manpower. Talks on such a force served political ends of coalescing European support around a security guarantee to Ukraine, but its feasibility depends on support from the US, whose “strategic enablers”—capabilities like air-to-air refueling, airlifting, and satellite-based intelligence and surveillance, and command and control—directly sustains NATO’s multinational coordinated posture on the eastern flank. Reports indicate that the US is tentatively open to extending these strategic enablers, similar to a division of labor during the 2011 Libya intervention, in which European troops utilized US ammunition, intelligence, and refueling. As the details are worked out, The Europeans will manage their ambitions depending on the scale of US involvement.
There are some limited options without any US involvement. The EU Common Foreign and Security Policy has integrated command structures, usually for small forces, that could act as a ceasefire monitoring mission or lead a train and equip mission at the Yavoriv Combat Training Center, the main site for the US training mission provided through the Ukraine Security Assistance Initiative (USAI) from 2014-2022. Alternatively, individual NATO allies, having institutionalized security cooperation with Ukraine through 32 bilateral agreements, could consider extending their own training missions with boots on the ground, perhaps coordinated by the informal Ukraine Defense Contact Group. NATO’s air policing mission in the Baltics could extend over Ukrainian territory, and Black Sea patrolling can provide a naval element to this as well. However, none of these options will carry the same weight as a US backstop or direct involvement, potentially risking a confrontation with Moscow if it decides to test the resolve of the European coalition.
Regardless of the specific format of a security guarantee, the Europeans will seek to advance Ukraine’s EU candidacy as part of a guarantee. EU membership provides an overlooked collective security arrangement through Article 42.7 of the Treaty on European Union, and candidacy status can provide an anchor into Western institutions, institutionalizing aid for industrial reconstruction, anti-corruption reforms, and creating military interoperability in tangent to the NATO framework. The US seems convinced on this point: US President Trump has called upon Hungarian Prime Minister Viktor Orban, an ideological ally irate over Ukraine’s attacks on Russian pipelines, to drop his objections to Ukraine’s accession.
The Risks: What Will the US Decide?
In the end, the US is the decisive actor. If it opts to adopt an active backstop, the Europeans will likely have the confidence to station a larger assurance force closer to the frontlines. If the US decides to leave the burden on Europe alone, an assurance force will likely be small and focused on military training, similar to USAI, which won’t hold any deterrent value by itself. In the latter scenario, the best Europeans can hope for is arming Ukraine and themselves to the teeth, reconstituting militaries capable of defending off a future Russian attack.
US openness to a security guarantee has grown largely in tandem to Ukraine’s economic diplomacy. In May, the two concluded a minerals agreement in which the US will reap the offtake returns from a reconstruction fund partnership, financed through future mineral revenues on Ukrainian territory and capital contributions, including in-kind transfers of defense articles. A predicted $350 billion in known mineral assets, including lucrative lithium reserves, are in occupied Ukrainian territories, giving the US an incentive to accept Ukraine’s war aims to restore complete control of its eastern regions. Since the most recent White House summit, Ukraine and the US are reportedly exploring a $90 billion arms sale that will include air defense systems (like US-made Patriot batteries) and $50 billion for the joint production of top-caliber Ukrainian drones with American defense firms. Such initiatives will further tie US commercial interests to the security of Ukraine, creating an indirect guarantee.
These events suggest that the US is inching toward a settled strategy on European security, but nothing is certain. In terms of political risks, the US may commit further diplomatic reversals, which would undermine Western military planning and ability to maintain a coherent position, giving license to Moscow to test allied resolve. In terms of macroeconomic risks, the strength of a security guarantee will correlate with Ukraine’s ability to raise capital for reconstruction, reconstitute its military, or implement anti-corruption reforms. A US backstop will also be key for allowing Europe to rearm and shift its industrial production lines toward defense articles. A weak security guarantee may add additional fiscal pressure to European budgets seeking to fill capability gaps, while diverting attention from Ukraine’s reconstruction and the US minerals deal. Frantic defense spending may come at the expense of state support to spread the risks of reconstruction investment, undermining Ukraine’s industrial base. Alternatively, a strong guarantee will enable long-term defense planning and procurement signals, creating opportunity for joint ventures between Ukrainian and Western defense firms.
