The Reliability Gap: America Is Still Powerful. Its Allies Are No Longer Sure That Matters

After decades of Washington urging its allies to shoulder greater responsibility over their national defence, the question now remains: what degree of autonomy is the United States comfortable in allowing? US policy outpacing military capabilities has led to a range of responses from various allied nations and international bodies across the globe. In turn, Washington must consider new institutional and diplomatic measures to provide consistent commitments, ensuring that allies need not reconsider security policies every four years.

Part 1: The Gap 

In August, President Trump abruptly ordered a substantial reduction in US–South Korean military exercises, citing both his relationship with Kim Jong Un and Seoul’s refusal to support US action against Iran. The decision immediately raised concerns in Seoul because a bilateral security arrangement was being linked to South Korea’s behaviour in an unrelated theatre (Toropin and Richer, 2026). For Seoul, the central question is whether it can confidently predict the terms on which Washington will use its military power.

This uncertainty can be understood through three related concepts. Capability concerns whether the United States has the means to defend its allies. Credibility concerns whether adversaries believe Washington would honour its commitments in a crisis. Reliability concerns whether allies themselves can build long-term security policy around the expectation that those commitments will remain stable. 

America’s alliance problem lies in the widening gap between what Washington can do and what its allies can confidently assume it will do. 

South Korea is one example of a wider regional concern. Reuters reported this week that officials and analysts across Japan, Taiwan, and India are reassessing how much they can depend on Washington following Trump’s moves towards North Korea and his increasingly transactional approach to regional partnerships (Geddie et al., 2026). Their concern centres on the predictability of American support and the conditions that may become attached to it. 

South Korea continues to value its relationship with the United States. Its foreign minister and Secretary of State Marco Rubio reaffirmed close cooperation only days after the dispute (Brunnstrom, 2026). Yet continued cooperation can coexist with greater caution. Allies may remain firmly within the American security system while preparing for circumstances in which Washington’s position changes unexpectedly. 

That uncertainty also affects deterrence. American commitments are observed by both allies and adversaries. Seoul wants to know whether Washington can be relied upon; Pyongyang wants to know whether Washington would actually intervene. If US commitments begin to appear more conditional or politically unstable, adversaries may see greater room to test them. 

This problem extends beyond the current administration. Allies have now experienced repeated shifts in American foreign policy across successive governments, particularly in areas such as NATO, Iran, trade, and multilateral cooperation. Even strong reassurance from a future president may therefore carry less weight than it once did, because allies know that another election can produce another sharp change in direction.

Dependence on the United States is therefore becoming something allies increasingly have to manage as part of their own security planning.

Part 2: The Response 

Allies are responding to greater uncertainty over Washington by building insurance into their security policies. The underlying calculation is straightforward: if American commitments become harder to predict, governments need enough capability and alternative partnerships to reduce the consequences of a sudden change in US policy. 

Europe provides the clearest example. European allies and Canada increased defence expenditure by nearly 20% in 2025, while the European Council has called for a rapid expansion of defence readiness and a reduction in strategic dependencies (NATO, 2026; European Council, 2026). This does not amount to replacing the United States. It gives European governments greater capacity to act when American support is delayed, constrained, or politically uncertain. 

Germany illustrates this shift. Berlin remains firmly committed to NATO, yet recent changes in the US force posture have reinforced the case for greater European responsibility. In May 2026, Washington announced the withdrawal of 5,000 troops from Germany with little prior consultation, while US officials linked the decision partly to Chancellor Friedrich Merz’s criticism of American policy towards Iran (Gray and Bayer, 2026). Russia remains the immediate driver of German rearmament, but uncertainty over Washington increasingly shapes the environment in which those decisions are made. 

France represents the more autonomous end of this response. President Emmanuel Macron’s 2026 nuclear doctrine expanded the European dimension of French deterrence, including greater participation by European partners in nuclear exercises and discussion of a more geographically distributed deterrent posture (Rose, 2026). The significance lies less in France replacing the American nuclear umbrella than in the fact that European governments are taking alternative forms of deterrence more seriously as confidence in US protection becomes less certain. 

Poland shows that insurance can work in the opposite direction. Rather than creating distance from Washington, Warsaw has sought to make the American commitment more permanent. In June 2026, the Polish government formally began preparations for a permanent US military base, describing a lasting American presence as a way to strengthen deterrence on NATO’s eastern flank (Government of Poland, 2026). Reducing uncertainty can therefore mean binding the United States more tightly to an ally as much as building independence from it.

A similar pattern is emerging in the Indo-Pacific, where countries are strengthening direct defence relationships alongside their US alliances. Japan and Australia have expanded military coordination and established a new framework for strategic defence cooperation, while Japan has increasingly presented itself as a connecting point for regional security partnerships (Japanese Ministry of Defence, 2025; Gopalakrishnan and Torode, 2026). Washington remains central to this network, but it is no longer the only relationship through which regional security cooperation operates. 

The common pattern is diversification. Allies are increasing their own capabilities, strengthening relationships with one another, and in some cases seeking to embed the US presence more deeply. These strategies differ, but they respond to the same problem: security planning increasingly has to account for the possibility that American policy may change faster than military capabilities can. 

That time-horizon mismatch makes adjustment difficult to avoid. Defence procurement and force planning unfold over decades, while American political leadership can change every four years. Governments cannot base long-term military choices on confidence in a single administration. Once continuity becomes less certain, strategic insurance becomes rational even for allies that remain strongly committed to the United States. 

For Washington, this creates an uncomfortable consequence. Stronger allies reduce the burden carried by the United States, but they also gain greater freedom to pursue their own priorities. America has spent decades asking its partners to assume more responsibility for their defence. It now has to decide how comfortable it is with the autonomy that greater responsibility inevitably creates.

Part 3: What Should Washington Do

If political volatility is widening the reliability gap, reassurance from individual presidents will not be enough to close it. Washington should instead make its commitments more durable and build an alliance system that can absorb changes in American politics without forcing allies to reconsider their security assumptions every four years. 

The first step is institutional. Congress has already demonstrated one way of doing this: under the FY2024 National Defence Authorisation Act, a president cannot unilaterally withdraw the United States from NATO without Senate consent or an Act of Congress (US Congress, 2024). Similar logic can be applied more broadly through multiyear defence funding, longer-term basing arrangements and regular allied consultation before major changes in force posture. These measures would preserve presidential flexibility while making abrupt reversals more difficult. 

Washington should also avoid turning security guarantees into instruments of unrelated political bargaining. Pressure on allies to spend more has produced substantial results. NATO allies agreed in 2025 to move towards spending 5% of GDP on defence and security-related priorities by 2035, while European allies and Canada increased defence expenditure by nearly 20% in 2025 (NATO, 2026). Burden-sharing therefore does not require making collective defence appear conditional on trade disputes or short-term political disagreements. 

Greater allied autonomy should be treated as an asset within the alliance system. NATO itself increasingly speaks of a more balanced transatlantic relationship in which European allies assume greater responsibility for their own defence while the United States remains engaged (NATO, 2026). A similar model is already visible in the Indo-Pacific, where the United States, Japan and Australia have expanded trilateral planning, exercises and operational coordination (US Department of Defence, 2025). Strengthening direct links among allies creates more capacity to respond without requiring Washington to coordinate every step. 

The political consequence is that stronger allies will also expect greater influence over strategy. They may occasionally pursue priorities that differ from those of the United States. Washington has spent decades asking its partners to carry more of the defence burden; accepting some loss of control is part of what successful burden-sharing looks like. 

Trying to resist that shift would deepen the reliability problem. Allies that are already reducing their exposure to American political uncertainty have little reason to become more dependent simply because Washington prefers a more hierarchical system. The better option is to shape greater autonomy so that it develops within existing alliances rather than outside them. 

The United States cannot remove political uncertainty from its foreign policy, but it can make the alliance system less vulnerable to it. That requires more durable commitments, stronger partners and a wider distribution of responsibility. American leadership may ultimately endure not by remaining indispensable in every crisis, but by creating alliances strong enough that its indispensability is no longer its greatest vulnerability. 

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