The upcoming NATO summit in Ankara is not the first meeting at which the alliance’s members have had to navigate internal tensions. Recent summits involving the Trump administration have often been tense, most famously in 2018, when President Donald Trump first began to threaten to leave NATO if other allies did not increase their level of defence spending.
However, tensions ahead of Ankara are at a much higher level than in previous years. This is because the Trump administration has become serious about reducing its level of involvement in European security, which has major ramifications for NATO. It is also partly a result of NATO moving to annual summits in response to the intensification of the threat level in Europe after the full-scale Russian invasion of Ukraine in 2022, which has created a stage for tensions to play out publicly.
NATO members will arrive in Turkey with several different points of disagreement between them. President Trump remains upset that other allies did not support the US war in Iran to the extent that he had desired. For his administration, this is an example of what they see as European security freeloading, as they believe that their action in the Middle East will benefit global security overall.
President Trump has also let his disappointment over Iran turn into significant disagreements with several European leaders, including the UK’s Prime Minister Keir Starmer, Italy’s Prime Minister Giorgia Meloni and Germany’s Chancellor Friedrich Merz.
All three of these leaders were relatively close with President Trump and were praised by him, but he has now publicly criticized them. With only days to go until the NATO summit, Merz has defended Germany’s defence spending record, Meloni has significantly distanced herself from Trump, and Starmer has focused on connecting with other European leaders to provide a counterbalance to the US.
Transatlantic defence tensions
This reflects the wider mood in Europe: 2025 was already a difficult year for the transatlantic relationship, but 2026 has been even more difficult to date.
The confusing US threats against Greenland in January and February shocked those who had not thought that the US would truly turn its back on NATO. Europe has become much more wary about Washington’s intentions. The US is now seen as an inconsistent ally with a short memory that does not remember Europeans’ support when the US called for Article 5 assistance after the 9/11 attacks.
US officials have also reportedly privately warned several European allies that their orders from American defence contractors will likely be delayed as Washington prioritizes replenishing its own stockpile after the Iran war, deepening the sense of the US turning away from Europe. These allies include the UK, Poland, Lithuania, Estonia and Germany, who are now put in a difficult position, especially given pre-existing concerns that Russia could pose a threat to NATO years before European states have sufficiently improved their military capabilities.
For Europeans, this shift justifies their focus on rebuilding European defence industrial capabilities. This will allow them to reduce their dependence on the US when it comes to new procurement contracts in the future.
However, this increasing independence will undoubtedly exacerbate tensions between the US and European allies in the future: While the US has encouraged its European allies to spend more on defence, there also seems to be an expectation that this will be in the form of them continuing to purchase American equipment. If the number of European orders reduces over time, the US might then not be so keen on a more independently secure Europe.
Washington’s announcements that it would be reducing troop and equipment deployments in Europe has also caused concern among allies that the US’s extended deterrence guarantee to the continent is no longer as firm.
The US is reportedly planning to affirm its ongoing commitment to Article 5 and extended deterrence at the summit in Ankara. However, it is legitimate to question the extent to which potential adversaries will continue to perceive NATO’s deterrence posture as credible if they can see the US disengaging from the continent. After all, a crucial tenet of Cold War thinking was that the US would not risk becoming involved in a nuclear war in Europe if it did not have any skin in the game; the same logic could also apply today.
Divide over managing Trump
Beyond the tensions between the US and European allies, inter-European tensions will also require careful management. As the US has become a more erratic ally, European views on how to manage the relationship with the US have diverged.
Ahead of the NATO summit in The Hague in 2025, there was some reluctance about NATO Secretary General Mark Rutte’s approach to managing Trump, which has been characterized by flattery. But the overwhelming view remained that if his methods led to results then the ends justified the means.
