European Nations Explore Collective Defense Arrangements Outside NATO Framework

From the Kensington Treaty to Macron's nuclear doctrine, the continent is scrambling to build a security architecture that doesn't depend on Washington. The price tag, the politics, and the precedents suggest the task is far harder than the rhetoric implies.

The Money Problem

The first obstacle is arithmetic. Bruegel and Kiel Institute researchers estimate that Europe would need to spend roughly €250 billion per year—approximately €1 trillion over four years—to credibly deter Russia without relying on American military power [1]. The International Institute for Strategic Studies (IISS) reached a similar conclusion, estimating it would cost $1 trillion to replace just the conventional U.S. military capabilities currently assigned to Europe [2].

European defense budgets have grown sharply in recent years. EU member states' combined defense expenditure rose from €198 billion in 2019 to an estimated €381 billion in 2025, according to the European Defence Agency [3]. But spending more money is not the same as spending it well.

Source: European Defence Agency

Data as of Dec 1, 2025CSV

The European Commission's Readiness 2030 package, launched in spring 2025, aims to mobilize €800 billion by the end of the decade—€650 billion from member states and €150 billion from the Commission in the form of loans through the Security Action for Europe (SAFE) instrument [4]. Whether these sums materialize, and whether they flow into the right capabilities, remains an open question.

The Capability Gaps That Money Alone Cannot Close

Even if European governments find the funds, specific capability shortfalls create dependencies on the United States that cannot be replaced quickly.

Air and missile defense is the most acute gap. The relocation of U.S. Patriot and Aegis Ballistic Missile Defense systems would sharply reduce Europe's ability to counter ballistic missile threats from Russia [5]. Ukraine's war demonstrated the centrality of integrated air defense, suppression of enemy air defenses, and advanced electronic warfare—areas where Europe currently lacks depth [6].

Strategic airlift and logistics present another bottleneck. European forces depend on American transport aircraft for rapid deployment and sustainment. NATO's capacity for moving forces quickly continues to rely on U.S. platforms [5]. Experts estimate it would take three to five years to close the aerial refueling and strategic airlift gap, and up to a decade for airborne surveillance [5].

Satellite intelligence may be the hardest gap to fill. The United States operates 246 military satellites, dwarfing the 49 managed by European NATO members combined [5]. Real-time surveillance, signals intelligence, and the capacity to act on strategic data constitute the backbone of modern military power, and Europe has not built autonomous networks capable of replicating American capabilities in this domain [5].

The EU's Defense Readiness Roadmap 2030, adopted by the 27 member states, outlines four flagship initiatives—Eastern Flank Watch, Drone Defense, Air Shield, and Space Shield—intended to address these gaps [7]. But ambition and operational capability are separated by years of procurement, training, and integration work.

The Legal Architecture: Article 42.7 and Its Limits

Any European defense arrangement outside NATO would need a legal foundation. The most frequently cited candidate is Article 42.7 of the Treaty on European Union, which states that if a member state suffers armed aggression on its territory, other members "shall have towards it an obligation of aid and assistance by all the means in their power" [8].

This language sounds robust, but its only invocation exposed its limitations. After the November 2015 Paris terrorist attacks, France activated Article 42.7 for the first time—the first use since the clause was introduced in the Lisbon Treaty in 2009 [9]. French Defence Minister Jean-Yves Le Drian described the move as "more than anything else, a political act," and Paris did not expect concrete military results [10]. The response from other EU members was voluntary and largely symbolic.

The contrast with NATO's Article 5 is instructive. Article 5 has binding institutional machinery behind it—integrated military command structures, standardized force planning, and decades of rehearsed collective defense procedures. Article 42.7 has no equivalent implementation framework. The Vrije Universiteit Brussel's Centre for Security, Diplomacy and Strategy has argued that Article 42.7 needs urgent operationalization if it is to function as a credible substitute for NATO's collective defense guarantee [11].

Additional legal instruments have emerged. The Kensington Treaty, signed by UK Prime Minister Keir Starmer and German Chancellor Friedrich Merz on 17 July 2025—the first bilateral treaty between the two countries since World War II—includes mutual assistance clauses and joint defense industrial cooperation, including development of a deep precision strike weapon with a range exceeding 2,000 kilometers [12]. But bilateral treaties, however significant, do not constitute a multilateral collective defense framework.

The 2% Milestone—and Why It's Not Enough

In 2025, all NATO allies met or exceeded the 2% of GDP defense spending target for the first time since the guideline was established [13]. This represented a dramatic shift from 2014, when only three members met the threshold.

Source: NATO

Data as of Aug 29, 2025CSV

But the milestone is less impressive on closer inspection. Half the alliance—16 countries—barely exceeded 2%, spending between 2.0% and 2.1% of GDP [14]. NATO itself has moved the goalposts, with allies agreeing at their most recent summit to a new target of 3.5% of GDP. Only Poland, Lithuania, and Latvia are on track to meet that standard [14].

The total European defense spending figure of 2.3% of combined GDP in 2025, up from 1.4% in 2014 [13], represents real progress. But closing the gap to genuine strategic autonomy requires not just more spending but different spending—joint procurement, interoperable systems, and coordinated force planning rather than 27 separate national shopping lists.

Nuclear Deterrence: The French and British Question

Europe possesses two independent nuclear arsenals—France's and the United Kingdom's. In theory, these could substitute for U.S. extended deterrence. In practice, the obstacles are formidable.

French President Emmanuel Macron announced a doctrine of "forward deterrence" that includes forward-basing nuclear weapons outside French territory and enhancing bilateral deterrence cooperation with select European partners, including Poland, the Netherlands, Belgium, Greece, Sweden, and Denmark [15]. France plans to increase the number of nuclear warheads in its arsenal for the first time since 1992, on the rationale that the current force is too small to project credible deterrence beyond French borders [15].

However, several countries conspicuously absent from Macron's partner list underscore the limits. The Baltic states, Norway, and Finland—the NATO members most directly exposed to Russian military pressure—were not included [15]. The most plausible conflict scenario involves a rapid Russian offensive against the Baltics to establish a fait accompli, and crossing the nuclear threshold in response would carry the risk of uncontrolled escalation [15].

Legal constraints also apply. Extending French or British nuclear guarantees to non-nuclear states would raise serious questions under the Nuclear Non-Proliferation Treaty (NPT), and Arms Control Association analysts have warned that such a move could mean "the treaty's death knell" [16].

The Carnegie Endowment for International Peace has noted that France and the UK might find extended deterrence easier to justify than Washington does, since a Russian invasion of Europe would pose a more direct existential threat to Paris and London than to the United States [17]. But credibility—the willingness to risk nuclear devastation for an ally—remains the central problem of any extended deterrence posture, and no European government has yet made the formal commitments that would test it.

The Sovereignty Trap: Who's Blocking Integration?

EU defense integration faces resistance from multiple directions, for reasons that go beyond simple unwillingness.

Germany faces constitutional barriers. The Federal Constitutional Court has ruled that participating in a European defense union with qualified majority voting would require a constitutional amendment—a high political bar in any country, and especially in Germany [18].

Greece and Cyprus have blocked Turkey's participation in EU military mobility projects, viewing Turkish integration into EU defense architecture as a threat rather than a contribution to security [19].

Hungary has used its veto power to obstruct defense initiatives it opposes, leading some EU officials to explore institutional workarounds that exclude non-participating members [19].

At a deeper level, national defense ministries across Europe resist ceding procurement authority. Member states routinely favor domestic suppliers to protect national industrial capabilities and employment, even when joint procurement would produce better equipment at lower cost [20]. Collaborative defense procurement remains below 20% of total spending, and the Defense Readiness Roadmap's target of reaching 40% by 2027 is widely viewed as ambitious [20].

The structural fragmentation of Europe's defense market creates what the IMF has estimated as a self-imposed cost premium of 45% in manufacturing [20]. The EU maintains 27 small, protectionist national defense markets, and efforts to consolidate them run into resistance from every capital that hosts a defense firm.

Procurement Nationalism vs. Strategic Autonomy

A persistent tension runs through Europe's defense debates: whether the push for "strategic autonomy" is building real military capability or primarily serving as cover for industrial protectionism.

Germany's 2025–2026 procurement plan allocated only 8% of its $83 billion annual defense budget to U.S. systems, directing the rest to national or European programs [21]. Intellectual property disputes, especially in high-tech and dual-use sectors, undermine trust and limit the scalability of collaborative projects [20].

The EU has framed its SAFE loan program to incentivize joint procurement by offering preferential terms to member states that buy equipment together [4]. But the incentive structure competes with the political imperative to protect national jobs and industrial capacity—a tension visible in every previous attempt at European defense consolidation.

Critics, including researchers at the European Centre for International Political Economy (ECIPE), argue that procurement nationalism fragments interoperability and raises costs without producing the integrated force structure that collective defense requires [20]. Proponents counter that building a European defense industrial base is itself a strategic necessity, reducing dependence on American suppliers who may not always be reliable partners.

A History of False Starts

Skeptics of the current push can point to a long record of European defense initiatives that generated acronyms but not operational capability.

The Western European Union (WEU), established in 1948, was meant to provide collective defense but spent most of its existence dormant, its functions absorbed by NATO and the EU. It was formally dissolved in 2011, having never mounted a significant military operation [22].

EU Battlegroups, created in 2007, consist of battalion-sized units of approximately 1,500 troops intended for rapid deployment. They have never been deployed in combat—not in the Democratic Republic of Congo in 2006 or 2008, not in Libya in 2011 [22]. The financing model ensured this outcome: the costs of deployment fall on whichever governments happen to be on rotation, giving those governments strong incentive to veto any operation [22].

Permanent Structured Cooperation (PESCO), launched in 2017 with 26 of 27 EU member states, was designed to drive structural defense integration. Its record is mixed. Beyond the military mobility project and a cyber response team deployed to Moldova, PESCO has been, in the words of analysts, "low-key" [23]. Many projects have stalled due to inadequate financial and practical planning. The broader EU defense institutional apparatus—CSDP, EDF, CARD, CDP, MPCC—has, as one assessment put it, "not yet led to any tangible shift in the Union's capability base or readiness for deployment" [23].

What structural reasons exist to believe this time will differ? Proponents point to the geopolitical shock of Russia's full-scale invasion of Ukraine, the uncertainty of U.S. commitment under the Trump administration, and the unprecedented scale of spending increases. These are real changes in the strategic environment. But the institutional and political incentives that undermined every previous effort—sovereignty reflexes, cost-sharing disputes, industrial protectionism—remain intact.

How Adversaries Calculate

If a European collective defense pact were formalized without the United States, how would potential adversaries respond?

Russia is the most immediate concern. Research from the Centre for European Policy Studies suggests that a "window of opportunity" may emerge if U.S. commitment evaporates or comes into doubt [17]. Europe would need to either increase troop numbers by more than 300,000 to compensate for the fragmented character of national militaries, or find ways to drastically enhance military coordination [17]. Failure to do either would risk presenting Moscow with a period of exploitable weakness.

Both Russia and China would prefer to deal with a less-integrated Europe [17]. The Kensington Treaty and similar bilateral defense pacts complicate the strategic calculus for both powers, but they do not replicate the deterrent weight of a unified alliance backed by the world's largest military.

Russia's initial response to the Kensington Treaty was a warning from Moscow, signaling that any deepening of European defense cooperation outside NATO will be treated as an escalatory development [12].

The transition period is the most dangerous phase. During the years when European defense capabilities are being built but have not yet reached credible levels, the gap between stated commitments and actual military power could invite the kind of probing that deterrence is meant to prevent.

What Comes Next

The EU's Defense Readiness Roadmap 2030 and the bilateral treaties now proliferating across Europe represent the most significant push for autonomous defense capability since the European Defence Community failed in 1954. The spending is real: €381 billion in 2025 and rising [3]. The political will, galvanized by Ukraine and sharpened by transatlantic uncertainty, is stronger than at any point in postwar history.

But the structural barriers are equally real. Capability gaps in air defense, strategic airlift, and satellite intelligence cannot be closed by 2030 [5]. Nuclear deterrence cannot be credibly extended without confronting NPT constraints and escalation risks [16]. Procurement nationalism inflates costs and fragments interoperability [20]. Constitutional limits, sovereignty objections, and industrial competition ensure that every step toward integration will be contested.

The question is not whether Europe needs greater defense self-sufficiency—that argument is effectively settled. The question is whether European governments can build integrated military capability at the speed the threat environment demands, while overcoming the political incentives that have defeated every previous attempt. The €1 trillion price tag is daunting, but the institutional transformation required to spend it effectively may be the harder challenge.