When NATO leaders gather in Ankara, they will do so at one of the most consequential moments in the Alliance's post-Cold War history. This summit is about far more than another debate over defence spending. It is about whether NATO can preserve the political cohesion that has underpinned the transatlantic alliance for more than seventy-five years while adapting to a rapidly evolving strategic environment.

Russia remains NATO's foremost military challenge, but it is no longer the Alliance's only strategic concern. The recent conflict between the United States and Iran demonstrated how instability in the Middle East can quickly disrupt global energy markets, threaten maritime commerce, and expose political divisions among allies. At the same time, uncertainty surrounding America's future military commitment to Europe has intensified long-standing debates over burden-sharing, alliance solidarity, and NATO's long-term purpose.

President Trump's New Grievance With Europe

For years, President Trump's criticism of NATO centred on burden-sharing. European allies, he argued, had become too dependent on American military power while failing to invest adequately in their own defence. That debate has not disappeared. Following the conflict with Iran, however, the White House has added a new grievance—political reciprocity.

From Washington's perspective, the United States expected stronger political backing from its closest allies during one of the defining foreign policy crises of President Trump's second presidency. While many European governments supported diplomacy, intelligence cooperation, and logistical assistance, the administration concluded that political solidarity from several allies fell short of expectations. No disagreement better illustrates that frustration than President Trump's deteriorating relationship with Italian Prime Minister Giorgia Meloni.

Long regarded as one of President Trump's closest European partners, Meloni nevertheless declined to fully align Italy with U.S. military operations against Iran, restricting the use of American facilities on Italian territory to defensive and logistical purposes. The disagreement, which became increasingly public following the G7 Summit, came to symbolize what the administration views as a broader reluctance among European allies to support American strategic priorities beyond Europe. For President Trump, Italy is not the issue. It is an example.

His administration increasingly argues that alliance solidarity must be reciprocal. European governments cannot expect the United States to maintain the Alliance's military backbone while remaining hesitant to defend American strategic interests elsewhere.

Many European governments reject that interpretation, arguing that NATO's primary mission remains the collective defence of the Euro-Atlantic area rather than supporting every American military operation beyond Europe. Yet regardless of which view ultimately prevails, this widening difference over the meaning of alliance solidarity is likely to define the political atmosphere in Ankara far more than another debate over defence spending.

The central question confronting NATO is therefore no longer simply how much allies should spend. It is what they should expect from one another in an era of increasingly interconnected security challenges.

The Five Percent Challenge

If one issue is guaranteed to dominate the formal agenda in Ankara, it is defence spending.

President Trump is expected to press NATO allies to move beyond the Alliance's long-standing benchmark of spending 2 percent of GDP on defence and embrace a far more ambitious target of 5 percent. While much of the debate has focused on whether such a figure is politically or economically achievable, doing so risks overlooking the administration's broader objective. For President Trump, the proposal is not simply about increasing defence budgets. It is a political test.

The White House increasingly argues that if European leaders genuinely believe Russia represents the greatest threat to continental security since the Cold War, then national budgets should reflect that reality. From Washington's perspective, the era in which the United States carried a disproportionate share of NATO's defence burden while many allies delayed difficult spending decisions cannot continue indefinitely.

For many European governments, however, reaching 5 percent would require difficult fiscal choices, sustained political support, and major reforms to defence procurement. Yet the debate extends well beyond budgets.

The war in Ukraine has demonstrated that modern deterrence depends not only on how much governments spend, but on what those investments produce. Ammunition stockpiles, integrated air and missile defence, drone production, cyber capabilities, military mobility, logistics, and resilient supply chains have become essential to sustained warfare.

Perhaps the Alliance's greatest lesson from Ukraine is the urgent need to rebuild its defence industrial base. For decades, many NATO members optimized their defence industries for efficiency rather than capacity. Ukraine exposed the shortcomings of that model, demonstrating how quickly modern conflict can exhaust missile inventories, artillery ammunition, and precision-guided munitions.

Increasing defence spending alone will not solve that problem.

If NATO cannot expand industrial production, accelerate procurement, and replenish military inventories, larger budgets will produce only marginal improvements in military readiness. Financial commitments must translate into deployable military capability.

Ultimately, the debate over 5 percent is not about accounting.

It is about whether Europe is prepared to assume a greater share of the strategic burden as the United States increasingly adopts a more reciprocal model of alliance leadership. Success in Ankara will therefore be measured not simply by another spending pledge, but by whether NATO can convert financial commitments into a credible military capability capable of sustaining collective defence over the long term.

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