For much of its history, NATO burden-sharing has been understood primarily as a political issue centred on fairness—how much each member contributes relative to the United States. Yet this framing no longer captures the strategic reality facing the alliance. Over the past decade, burden-sharing has evolved from a debate about financial equity into a structural question about NATO’s ability to deter and, if necessary, fight a peer adversary.
At the heart of this shift lies a fundamental asymmetry. NATO is formally a collective organisation, but in practice it remains functionally dependent on the United States for a disproportionate share of high-end military capabilities. Nowhere is this more evident than in the nuclear domain. NATO’s nuclear deterrent is overwhelmingly based on the US strategic arsenal, including intercontinental ballistic missiles, submarine-launched ballistic missiles, and long-range strategic bombers. While the United Kingdom and France maintain independent nuclear forces, these remain limited in scale and are not fully integrated into NATO’s nuclear planning structures. As a result, the credibility of deterrence against a nuclear peer such as Russia ultimately rests on the assumption of US retaliation.
This dependence extends beyond nuclear forces into NATO’s operational architecture. Even where European allies contribute significant troop numbers, NATO command structures have historically relied on US leadership, planning systems, and interoperability frameworks. The alliance’s effectiveness is therefore not simply a function of aggregate manpower, but of the systems that enable those forces to operate cohesively. These systems—often referred to as strategic enablers—are overwhelmingly provided by the United States.
Among the most critical of these is intelligence, surveillance, and reconnaissance. The United States supplies space-based surveillance through satellites, high-altitude drone capabilities, and signals intelligence that together provide real-time battlefield awareness. European capabilities in this domain remain limited, characterised by fragmented intelligence systems and insufficient satellite coverage. Without US’s intelligence and surveillance (ISR), NATO would face a severe degradation in situational awareness and early warning capabilities, undermining both deterrence and operational effectiveness.
A similar imbalance exists in strategic mobility. NATO relies heavily on US airlift and sealift capabilities, including large-scale transport fleets that enable the rapid movement of forces across the European theatre. This is particularly important for reinforcing NATO’s eastern flank. European capacity in this area remains comparatively limited, constraining the alliance’s ability to deploy forces quickly in the absence of US support. Air-to-air refuelling presents a comparable challenge. The United States provides the majority of tanker capacity within NATO, enabling sustained air operations over long distances, whereas European fleets remain insufficient to support comparable levels of operational reach.
The United States also plays a central role in space and cyber capabilities, as well as in integrated air and missile defence. Advanced US missile defence systems and networked architectures are critical for protecting NATO territory against modern missile threats, particularly from Russia. European air and missile defence systems, by contrast, remain insufficiently integrated and lack comprehensive coverage. This creates vulnerabilities that cannot easily be addressed through increased spending alone.
Equally important are NATO’s command-and-control systems. The United States provides multi-domain command structures, data fusion networks, and battle management systems that enable the coordination of multinational forces. These systems are essential for integrating European tanks, aircraft, and personnel into a coherent operational framework. Without them, NATO’s forces would struggle to function effectively as a unified military entity.
The imbalance is further reinforced in the domain of high-intensity warfighting. While European countries possess significant conventional forces, they lack key capabilities required for modern warfare at scale. In particular, Europe has insufficient long-range precision strike capacity. By contrast, the United States provides long-range cruise missiles, stealth bombers, and advanced strike systems capable of targeting adversary infrastructure deep within contested environments. These capabilities are central to achieving escalation dominance and shaping the battlefield in high-intensity conflict.
Historically, this asymmetry was not perceived as a strategic problem. NATO was designed as a US-led alliance, reflecting broader patterns of American primacy in the international system. During the Cold War, US military dominance was both expected and accepted, as it compensated for European limitations while confronting a stable adversary in the Soviet Union. Following the end of the Cold War, this arrangement persisted. Europe faced no immediate peer competitor, allowing NATO to shift its focus toward crisis management operations in regions such as the Balkans and Afghanistan. During this period, US nuclear and conventional superiority ensured that European capability gaps did not translate into strategic vulnerability.
However, underlying trends gradually eroded this equilibrium. The United States dramatically increased defence spending following the attacks of 11 September 2001, investing heavily in advanced military capabilities. Europe, by contrast, reduced defence expenditure, particularly after the 2008 financial crisis. This divergence resulted in the hollowing out of European armed forces, including reductions in heavy equipment, readiness levels, and industrial capacity. By around 2010, the United States accounted for approximately 65 to 70 percent of total NATO defence spending, while European forces increasingly prioritised lighter, expeditionary capabilities. At the time, this shift appeared rational, as Russia was not yet widely perceived as a full-scale peer threat.
This perception changed decisively in 2014 with Russia’s annexation of Crimea and its intervention in eastern Ukraine. These events marked a return to high-intensity, technologically complex warfare in Europe and exposed the extent of NATO’s capability gaps. Effective deterrence now required heavy armour, integrated air and missile defence, robust logistics, and the ability to conduct sustained high-intensity operations. European allies were found to lack not only sufficient strategic enablers—such as ISR, airlift, and refuelling—but also the readiness, ammunition stockpiles, and industrial capacity necessary for prolonged conflict.
Between 2014 and the early 2020s, the burden-sharing debate therefore underwent a fundamental transformation. What had previously been a question of equitable contribution became a question of NATO’s independent ability to deter and fight a peer adversary. This shift was further reinforced by the evolving global posture of the United States, which increasingly prioritised strategic competition with China in the Indo-Pacific. As a result, the assumption that the United States would remain the sole and unconditional security provider in Europe became less certain.
It was within this context that the first administration of President Donald Trump brought renewed attention to burden-sharing, framing the issue in explicitly financial terms. The emphasis on the 2 percent of GDP defence spending benchmark reflected a transactional approach to alliances, in which contributions were evaluated primarily in terms of monetary inputs rather than strategic outputs. Trump argued that the United States was “paying more than its fair share,” while European allies were failing to meet their obligations, at times suggesting that they “owed” the United States for its security guarantees.
The appeal of the 2 percent benchmark lay in its simplicity. It provided a clear, visible, and easily comparable metric that could be used to exert political pressure. However, it also obscured important realities. The same percentage of GDP can translate into vastly different levels of military capability depending on the size of an economy. For a large economy such as the United States, 2 percent represents a substantial share of global military power, accounting for roughly 60 percent of NATO defence spending. For smaller European economies, the same percentage yields far more limited capabilities.
More fundamentally, the 2 percent target measures inputs rather than outputs. It does not capture whether spending translates into usable military power. As former NATO Secretary General, Jens Stoltenberg emphasised, burden-sharing cannot be reduced to financial contributions alone. Capability-based approaches require long-term planning, multinational coordination, and technical integration. Focusing on aggregate spending risks encouraging inefficient allocation of resources, including increased expenditure on personnel or infrastructure that adds little to combat effectiveness.
This limitation has become increasingly evident. Even as defence spending has risen across NATO, key capability gaps persist. Countries meeting the 2 percent benchmark may still lack integrated command structures, effective interoperability, air and missile defence systems, ISR capabilities, strategic lift, and long-range strike assets. Readiness remains uneven, with questions about how quickly forces can be deployed and sustained in a crisis. Industrial capacity also remains a constraint, particularly in terms of ammunition production and the ability to sustain prolonged operations.
These challenges are compounded by structural inefficiencies within European defence. The existence of multiple parallel systems, lack of standardisation, and fragmented procurement processes continue to limit the effectiveness of increased spending. At the national level, defence reviews such as the United Kingdom’s Strategic Defence Review have emphasised the need for warfighting readiness, integrated and deployable forces, procurement reform, and the scaling of industrial capacity. These priorities reflect a broader recognition that rebuilding European military capability is a strategic, rather than purely financial, challenge.
As a result, NATO has begun to move beyond the 2 percent benchmark. Even after all member states reached this threshold by the mid-2020s, the alliance shifted toward higher spending targets and a greater emphasis on capability development. This includes investments in infrastructure, resilience, and the defence industrial base, as well as a focus on specific capability targets such as force readiness and logistical capacity. The emphasis is increasingly on “spending smarter,” ensuring that resources are directed toward areas that enhance operational effectiveness.
This shift reflects a deeper strategic reality. For Europe to achieve genuine autonomy within NATO—or to operate independently of the United States—it would require not only increased spending but also substantial structural reform. This would involve integrating defence industries, coordinating procurement, and investing heavily in the strategic enablers that are currently provided by the United States. The scale of this challenge is significant, requiring both political cohesion and sustained investment over time.
In this context, the evolution of the burden-sharing debate can be understood as part of a broader transformation in NATO’s strategic environment. What was once a manageable imbalance has become a central challenge to the alliance’s credibility. The issue is no longer simply whether allies are contributing fairly, but whether NATO as a whole possesses the capabilities required to deter aggression and sustain high-intensity conflict.
Ultimately, the effectiveness of NATO deterrence will not be determined by spending targets alone. It will depend on the alliance’s ability to translate financial resources into integrated, deployable, and sustainable military capabilities. Until these structural gaps are addressed, the tension between spending and capability will remain at the core of NATO’s strategic dilemma.
