NATO's Burden-Sharing Gap: US Disproportionately Anchors Alliance Deterrence

In 2025, for the first time since NATO adopted its 2% of GDP defense spending guideline, all 32 member nations met or exceeded the target [1]. The milestone arrived eleven years after allies made the pledge at the 2014 Wales Summit — a period during which non-US members collectively underspent by an estimated $827 billion in 2024 dollars [2]. That figure, nearly equivalent to a full year of US defense spending, has become a political lightning rod. But behind the headline number lies a more complex accounting of who contributes what, why spending alone misses the picture, and what happens if the alliance's linchpin steps back.

The Spending Ledger: From Three to Thirty-Two

When NATO leaders gathered in Wales in September 2014, only three members — the United States, the United Kingdom, and Greece — met the 2% threshold [1]. Progress was glacial for years. By 2018, eight allies qualified. By 2023, still only eleven [1].

Source: NATO Official Statistics

Data as of Jun 1, 2025CSV

Russia's full-scale invasion of Ukraine in February 2022 broke the logjam. European allies and Canada increased defense spending by 20% in 2025 alone [1]. Poland surged to 4.5% of GDP, Lithuania to 4%, and Latvia to 3.7% [1]. At the June 2025 Hague Summit, allies agreed to a new target: 5% of GDP by 2035, encompassing core defense and broader security-related spending [1].

Yet the cumulative deficit remains stark. Germany alone underspent by $249 billion relative to the 2% target between 2014 and 2024. Italy and Spain each fell short by roughly $150 billion. Canada's shortfall reached $80 billion [2].

Source: Heritage Foundation

Data as of Apr 1, 2025CSV

The average NATO European member spent just 1.59% of GDP on defense over the past decade [2]. The equipment spending gap — money specifically for procurement and modernization — amounted to an additional $71 billion below minimum thresholds [2].

Beyond Percentages: The Capability Asymmetry

The 2% metric captures inputs, not outputs. The United States accounts for approximately 62% of NATO's total defense expenditure, spending an estimated $980 billion in 2025 compared to Europe's $559 billion [3][4]. But the asymmetry in actual military capabilities is even more pronounced than the spending ratio suggests.

Source: SIPRI / NATO

Data as of Dec 1, 2025CSV

Strategic airlift: The US operates the world's only fleet of C-17 Globemaster III heavy-lift aircraft capable of deploying armored vehicles and large formations across intercontinental distances. No European nation possesses an equivalent; the multinational C-17 Strategic Airlift Capability consortium operates just three aircraft shared among twelve nations [5].

Nuclear deterrence: The US extends its nuclear umbrella over NATO through forward-deployed tactical weapons in Europe, strategic bomber forces, and submarine-launched ballistic missiles. France and the United Kingdom maintain independent nuclear arsenals, but these are not formally committed to NATO's integrated nuclear planning in the same way [6]. Replacing the American nuclear guarantee would require either massive expansion of French and British arsenals or a politically explosive move toward German or Polish nuclear weapons programs.

Intelligence and surveillance: US satellite constellations, signals intelligence networks, and drone operations — including those controlled from Ramstein Air Base in Germany — provide situational awareness that European allies cannot independently replicate [7]. The cost of building equivalent space-based intelligence architecture alone has been estimated in the hundreds of billions of euros.

Precision-strike munitions: The war in Ukraine exposed Europe's severe shortage of guided munitions and air defense interceptors. NATO planners have acknowledged the alliance possesses only 5% of the air defense capacity needed to adequately protect its eastern flank [8].

The Forward Presence: 68,000 Troops and Counting

As of May 2026, approximately 68,064 active-duty US military personnel are permanently stationed across Europe [9]. Germany hosts the largest concentration at roughly 36,400 troops, followed by the United Kingdom with 10,000 and Spain with 3,800 [9].

This represents a fraction of Cold War levels, when over 300,000 US service members were based in Europe. The number fell below 65,000 after post-Cold War drawdowns but climbed again following Russia's 2022 invasion, with additional rotational brigades deployed to Poland and the Baltic states [9].

The annual cost to US taxpayers is substantial. The European Deterrence Initiative alone was funded at $2.91 billion in fiscal year 2025, covering rotational brigade deployments, prepositioned equipment sets, and airfield improvements across eastern NATO [9]. Total costs including personnel, operations, and maintenance run significantly higher. The FY2026 NATO Security Investment Program budget request added $481.8 million for infrastructure projects [9].

The 2026 National Defense Authorization Act set a statutory floor of 75,000-76,000 US troops in Europe, though the Pentagon announced in May 2026 a withdrawal of approximately 5,000 troops from Germany following a political dispute between the Trump administration and German Chancellor Friedrich Merz [9][10].

The Conversion Problem: Why Money Doesn't Equal Readiness

Even allies spending heavily face structural barriers to translating budgets into deployable capability.

Germany's procurement bottleneck: Germany's 2025-2026 procurement plan allocates $83 billion annually, but analysis from the Atlantic Council warns funding is "likely to dry up after 2026," leaving a potential gap of €30 billion [11]. The constitutional debt brake — which limits federal borrowing — blocked earlier spending increases and contributed to the collapse of the governing coalition in December 2024 [12]. Although a subsequent reform loosened borrowing rules for defense, the industrial base cannot absorb orders fast enough to meet NATO's timeline requirements.

France's political paralysis: President Macron lost his parliamentary majority in 2024 summer elections, leaving the 2025 defense budget stuck at 2024 levels with a planned €3 billion increase in limbo [12]. France intends to reach 3.5% of GDP but faces a debt-to-GDP ratio of 113.1% [12].

Poland's industrial strain: Despite devoting 4.7% of GDP to defense — NATO's highest share — Poland's domestic defense group PGZ has struggled to fulfill orders on the timelines military planners demand, forcing reliance on foreign procurement, particularly South Korean platforms [11].

Broader industrial fragmentation: Europe operates 178 different weapons systems compared to 30 in the United States [13]. McKinsey estimates that Europe faces an "€800 billion Gordian knot" of fragmented procurement that reduces buying power [13]. NATO planners privately acknowledge that raw spending figures obscure wide gaps in readiness, interoperability, and force generation timelines. The alliance estimates it needs 35 to 50 additional brigades to fully realize its new defense plans [8].

The Counter-Narrative: What "Free-Riding" Misses

Critics of the free-rider framing point to several allied contributions that GDP percentages do not capture.

Ukraine assistance: As of February 2025, European allies and Canada had allocated $87 billion in bilateral assistance to Ukraine — 31% of total aid. Including EU institutional contributions, the European share rises to $141 billion, or 49% of total global support [14]. This represents a direct investment in degrading Russia's military capacity, NATO's primary adversary.

Host-nation infrastructure: The United States operates approximately 31 persistent bases and 18 other military sites across Europe [7]. These installations — which support Middle East operations, submarine tracking, ballistic missile early warning, and drone command — serve American global power projection far beyond European defense. Admiral James Foggo has warned that losing access to these bases would represent a downgrade "from global to regional power status" [7]. Host nations provide land, facilities, and legal frameworks often at minimal or no cost to the US. Poland has committed to funding infrastructure projects at 11 bases and training ranges under its Enhanced Defense Cooperation Agreement with Washington [7].

Sanctions costs: European nations bear disproportionate economic costs from Russia sanctions, having severed energy relationships that once supplied 40% of their natural gas. The trade disruption and energy price shocks of 2022-2023 imposed GDP losses estimated at 1-2% across the EU — costs not reflected in defense spending statistics [14].

Combat personnel in expeditionary operations: In Afghanistan, European allies sustained combat casualties alongside US forces over two decades. The UK, France, Germany, and smaller nations provided tens of thousands of troops to ISAF, with non-US allies comprising the majority of the coalition at various points [14].

The Baltic Test: What Happens If the US Steps Back?

The most consequential question is whether NATO can defend its most exposed members without full American participation.

A landmark 2016 RAND Corporation wargame found that Russian forces could reach the outskirts of Tallinn or Riga within 60 hours, and that NATO "cannot successfully defend the territory of its most exposed members as presently postured" [15]. RAND assessed that seven brigades, including three heavy armored brigades with adequate air and fire support, could prevent a rapid overrun [15].

Since then, NATO has shifted from "forward presence" to "forward defense," deploying multinational battlegroups to each Baltic state and Poland. A 2025 analysis published in the European Security journal modeled scenarios without US participation, concluding that three well-equipped European divisions (45,000 troops), combined with Baltic states' active and reserve forces (95,000 troops) and fortified borders, would give "a good fighting chance" at holding territory until reinforcements arrive [8][16].

However, the European Council on Foreign Relations assessed that Russia could not succeed in an invasion scenario for five to ten years after the Ukraine war ends, even with minimal US assistance — suggesting the immediate threat is lower than often assumed, though the gap could widen if European rearmament stalls [16].

NATO estimates it still lacks the 35-50 additional brigades needed for comprehensive eastern defense [8]. A US reduction of 25-50% in contributions — particularly in intelligence sharing, nuclear guarantees, and air superiority — would leave the most acute gaps in integrated air and missile defense and long-range precision strike [8].

Comparison With Asian Alliances

NATO's burden-sharing tensions are not unique. Japan spent 1.4% of GDP on defense in 2024 — its highest since 1958, following a historic decision to double military spending — but still below the NATO European median of approximately 2% [4][17]. South Korea, by contrast, spends roughly 2.7% of GDP, exceeding most NATO European members [17].

Source: World Bank Open Data

Data as of Dec 31, 2024CSV

Host nations in both regions contribute substantial financial support for US basing. Japan's "host nation support" payments cover a significant portion of US facility costs on its territory. The pattern suggests the commitment gap is not unique to NATO but systemic to US alliance management: Washington provides the security architecture, allies contribute less than Washington believes appropriate, and periodic political crises force renegotiation [17].

The key difference is that NATO has formalized its expectation through the 2% guideline (now 5%), creating a measurable accountability mechanism that Asian alliances lack. This formalization has paradoxically made the gap more politically visible while simultaneously driving faster convergence.

The Politics of Rearmament

The domestic obstacles to higher European spending are formidable but eroding.

Fiscal constraints: Several strategically important NATO members carry debt loads above 100% of GDP — Greece at 150.9%, Italy at 135.3%, France at 113.1%, and the UK at 101.3% [12]. Reaching the new 5% target would require some of these nations to more than double their defense budgets while servicing existing debt, a tension that finance ministries in Rome, Madrid, and Brussels have resisted.

Industrial absorption capacity: Even with unlimited funding, European defense firms cannot produce at the required scale. Order backlogs stretch years into the future. Ammunition production, while expanding, remains well below wartime consumption rates demonstrated in Ukraine [13].

Political culture: Germany's post-war strategic culture long treated military restraint as a virtue. The February 2022 Zeitenwende speech by then-Chancellor Scholz marked a rhetorical break, but institutional change has been slower. Coalition politics in Berlin, Rome, and other capitals continue to pit defense hawks against social spending advocates and fiscal conservatives [12].

Shifting balance: The power dynamics have moved decisively since 2022. Pacifist parties have lost influence across Europe. Poland's cross-partisan consensus on defense spending is the most dramatic example, but even traditionally reluctant nations like Belgium and Spain are now meeting the 2% threshold for the first time [1]. The question is whether this momentum can be sustained through the years-long procurement cycles needed to close actual capability gaps.

What the Numbers Cannot Settle

The burden-sharing debate is ultimately about political expectations as much as military accounting. The United States spends 3.4% of GDP on defense, but much of that spending supports Pacific, Middle Eastern, and homeland missions unrelated to NATO [4]. Allies argue — with some justification — that counting the entire US defense budget against NATO overstates the imbalance.

Conversely, American critics argue — also with justification — that a decade of underinvestment left Europe unable to credibly deter Russia without American leadership, validated by the scramble to arm Ukraine and reinforce eastern borders after February 2022 [2].

The 2025 milestone of universal 2% compliance represents genuine progress. Whether allies can sustain this spending, translate it into usable capability, and meet the far more ambitious 5% target by 2035 will determine whether the alliance's deterrence architecture remains coherent — or whether the commitment gap simply migrates from a spending shortfall to a capabilities one.