International Security Middle East United States

The Iran-Israel War and the Transatlantic Divide: Implications for NATO Cohesion

Noor Almutawwa 12 Jun 2026
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International Security Middle East United States

The Iran-Israel War and the Transatlantic Divide: Implications for NATO Cohesion

Noor Almutawwa 12 Jun 2026

On 28 February 2026, the United States and Israel launched a coordinated military strike on Iran, which the U.S. officially designated “Operation Epic Fury”. The strike targeted military bases and infrastructure, in addition to the senior leadership of the Islamic Republic. The early strikes killed the Supreme Leader Ali Khamenei, along with many high-ranking officials. Iran retaliated by launching drone and missile attacks on Israel and U.S. military bases across the Gulf region while also launching attacks on civilian and energy infrastructure within the Gulf Cooperation Council (GCC) states. Moreover, Iran moved to close the Strait of Hormuz, causing the most serious disruption to the global energy market since the 1970s oil embargo. This conflict followed the twelve-day war of 2025 and the prolonged period of nuclear negotiation between the United States and Iran held in Oman. This has been the most consequential escalation in the Middle East for several decades. From NATO’s perspective, the conflict presented a serious institutional strain, where a member state of the organization had initiated a major conflict without the collective authorization of the alliance, while also proceeding in the face of visible European unease.

The reaction of the European NATO members to the 28 February military strike was instant. France, the United Kingdom (UK), and Germany issued a joint statement condemning Iranian attacks in the region and calling for diplomacy. In addition, they reiterated their position on the nuclear program and demanded that Iran abandon the program and end the support of armed groups across the region. [1] However, beneath this unity lay a division within the organization. France took a critical stance when President Emmanuel Macron warned that military action carried out outside of international law would risk disrupting the global order and called for an emergency discussion at the United Nations. While the UK provided military support in the region, it stated that it did not participate in the strikes and had initially not allowed the United States to access the Diego Garcia base. [2] On the other hand, Germany took a different stance from both France and the UK when Chancellor Friedrich Merz approved the U.S.-Israel goal of ending what he labelled as the Iranian regime’s “terror”. This stance placed Berlin closer to Washington than other parties. NATO members, with their stance, maintained a managed distance instead of unity. Across the alliance, many members called for de-escalation and did not approve of the war initiated by NATO’s leading power.

This insight explores how NATO’s response to the U.S.-Israel-Iran war highlights a profound division in the alliance, especially between the United States and European states. This division is not simply about disagreement over burden-sharing, but it reflects a fundamental gap between the U.S. and Europe’s strategies in their views of security and the purpose of the alliance. This insight has four sections. Firstly, it explores the different interests between the United States and Europe and the rising tension in the alliance caused by the conflict. Secondly, it discusses the Iranian nuclear deal fallout in 2018 with the U.S. withdrawal, followed by U.S. military strikes on Iran in 2025. Thirdly, it analyzes arms supply disagreement between European members and the United States. Lastly, it explores what it all means for NATO.

Divided strategies: U.S. operation and European hesitation

The United States started a major military operation against Iran without prior consultation with its European allies, while also expecting to have their general support as well as access to their military bases. Europe was forced to instantly respond to a conflict it did not prepare for and in which it had no influence. The lack of consultation is not a trivial issue. It is essential to explain the European response and the differences growing within NATO. [3] The United States held two positions within the alliance. It is both a member of NATO that is committed to collective defense and an active participant in the conflict with Iran. This creates a foundational strain that NATO’s existing structure cannot manage. Article 4 of the North Atlantic Treaty states that members must consult the alliance whenever one member believes its security is at risk. NATO was built on the principle of collective decision-making and defense. Moreover, major military operations by one member must include a previous discussion, especially if these military actions will cause regional and economic instability that would affect all members. However, the operation launched in Iran did not adhere to that principle. As the former U.S. ambassador to NATO Ivo Daalder stated, there were opportunities to involve NATO members in the discussion about putting pressure on Iran, yet the United States chose not to. [4]

The difference in interest between the United States and its European allies is fundamental. For the United States, the Iran war accomplished several strategic goals. The Trump administration was articulate about some of these objectives, e.g., preventing Iran from any nuclear capabilities, seeking regime change in Iran, and proving the credibility of the U.S. military deterrence. These objectives reflect that the strategy of the U.S. is a coercive deterrence approach. There is a deep-rooted belief that the use of force can achieve security outcomes that diplomacy alone is unable to. On the other hand, the European governments function in a more conventional manner, where they put emphasis on solutions through diplomacy, legal norms and negotiations. This difference leads to different risk assessments when considering the use of military force against a state. The Iran conflict creates a distinct set of risks and costs to Europe more than to the United States. The blockade of the Strait of Hormuz caused an immediate and deep energy crisis. Brent crude oil price rose above US$100  per barrel. This is the most significant global energy shock since the 1970s oil embargo. [5] Europe depends more on the Gulf for oil supplies than the United States and has suffered a major consequence.

In addition to the energy issues, European countries, including Germany, Spain and the UK, faced public opposition to the strikes in Iran. Simultaneously, European states faced legal issues regarding whether their support for the United States in the conflict would line up with their commitment to international law. Experts argued that the U.S.-Israel strikes against Iran violate Article 2(4) of the UN charter, which prohibits the use of force against the territorial integrity of any state. It also does not give a valid justification for self-defense under Article 51. Europe operates within a legal framework, and these issues were politically consequential. [6]

Among the European members, responses were divided. France, Germany, the Nordic states, and the UK voiced some level of concern and called for de-escalation, and that comes from states that are more concerned about legal norms and economic exposure to the energy and trade in the Middle East. On the other hand, the Baltic states were fully in support of the strikes. That demonstrates their opposition to Iran being a supplier of drones to Russia and their geographical proximity to Russia. Moreover. Spain and Türkiye were the only members to take a stance against the military operation. These different responses reflect strategic perspectives shaped by different political interests. Throughout Trump’s administration, European allies dealt with the United States by accommodating his demands with a degree of distancing and political resolve. However, the Iran conflict has pushed this balanced distance to its limit. The United States is no longer concerned about the general support of a policy position. Thus, its allies are in a position forced to accept this military operation that they view as economically costly and legally uncertain.

JCPOA Collapse and the 2025 strikes: setting the stage for transatlantic tension

The JCPOA breakdown and the rise of transatlantic division

The gap between the United States and Europe within the alliance started way before the U.S.-Israel military operation against Iran. It had been building up over time when two major events happened. The first was the withdrawal of the United States from the Joint Comprehensive Plan of Action (JCPOA) in 2018 and the U.S. strikes on Iran’s nuclear sites in 2025. In both events, the United States acted on its own, while European allies objected but could not influence the outcome. Thus, this causes the gap of disagreements within the alliance to grow and becomes increasingly more difficult to resolve.

On 8 May 2018, the United States, under Trump’s administration, announced its withdrawal from the JCPOA. This was a unilateral decision. The decision was not based on any violation of the agreement by Iran, as confirmed repeatedly by the International Atomic Energy Agency (IAEA). However, the Trump administration viewed this agreement as one-sided and not strong enough, believing that Iran was benefiting economically while still pursuing its nuclear ambitions. [7] For Europe, this was more than just a policy disagreement. It indicated that the United States was willing to abandon multilateral diplomatic efforts without consulting its allies, considering their strategic priorities, or their diplomatic efforts to have better relations with Iran. [8]

In response, France, Germany, and the UK chose to remain in the agreement and later created INSTEX in January 2019 to allow limited trade with Iran and bypass the U.S. sanctions. INSTEX signaled that European countries are willing to act away from what aligns with the U.S. policy. It reflected readiness to challenge the U.S. presence and to create a system that can effectively work around it. This marked a significant shift between the allies. It was the first time since the Cold War that these European countries acted collectively to build a system that countered the U.S. policy in security-related matters. However, the limits for Europe’s financial independence became immediately clear. Later that year, the trade between Europe and Iran dropped by 71.5%. Even after six more European countries joined, the INSTEX had reportedly completed only one transaction. [9] The drop was caused by the United States reimposing higher sanctions, which prevented Europe from acting freely in financial terms.

Therefore, after the JCPOA, the transatlantic relations on Iran have effectively broken down. There was a willingness from Europe to resist U.S. unilateral actions. But they did not have enough structural influence to make that resistance effective. This returned to the same cycle in which Europe objected to and expressed disagreement with the U.S. decisions, but their efforts were limited by the United States’ economic influence, leaving these disagreements unresolved. European countries came to understand that Washington can make serious decisions on Iran without involving them and that the multilateral system they had invested in could be undone by the U.S.

The 2025 U.S. strikes and Europe’s cautious response

Furthermore, in June 2025, the United States carried out major strikes on Iran’s nuclear sites. The operation, called “Operation Midnight Hammer”, targeted three nuclear facilities, including Fordow, Natanz, and Isfahan. These strikes happened during the twelve-day war between Israel and Iran, when Israel could not hit the deeply protected underground sites. The United States moved beyond supporting Israel with intelligence and logistics; it has directly attacked Iranian territory. What signified a new level of the U.S. military involvement was the attack on the heavily protected Fordow facility. [11] This was a major escalation, yet it took place with very minimal discussion within NATO.

The European response was cautious and restrained. European leaders avoided directly supporting the operation while also avoiding condemning it. For example, the President of the European Commission, Ursula Von der Leyen, stated that Iran should not obtain nuclear weapons, which in a way aligned with the objective of the strikes. However, the legality of the operation was not addressed. [12] The UK has repeatedly stressed that it was not involved in the operation. Moreover, France avoided supporting the strikes while also not directly condemning them. Collectively, France, Germany, and the UK called for de-escalation and returning to negotiations, stressing diplomatic solutions over military action.

For more than two decades, Europe had tried to prevent any escalation with Iran, mainly because of concerns related to migration and risks to energy supplies. However, when the strikes occurred, any form of diplomacy from Europe did not have any influence on the event. Europe had no mechanism within the alliance to limit the actions of the United States. Although a ceasefire was reached later, on the 24 of June, negotiations resumed afterward. Yet, the disagreement between the United States and Europe was not resolved. Thus, when the strikes on Iran in February 2026 occurred, Europe adopted the same cautious response, given its previous experience that had shown that this was its only available option.

Arms supply disputes and the limits of NATO’s solidarity

Statements from European countries calling for de-escalation can be managed within the alliance with cautious wording. However, taking a stance on the matter of arms export decisions is entirely different. When several NATO members choose to limit or end the supply of weapons to a country that is an ally of a NATO member, that solidifies the disagreement, turning words into solid policy. Thus, the lack of unity within the alliance becomes visible. The arms restrictions began during the Gaza conflict and have gradually increased since then throughout 2024 and 2025. There are several reasons for these restrictions. Firstly, the legal pressure on European countries comes from activists and legal experts using both domestic and international law. [13] Secondly, parliamentary debates in the UK call for the suspension of arms supplies to Israel amid concerns about international humanitarian law violations. [14] And lastly, there is growing public concern across Europe. As the United States continued to be the main supplier to Israel and provider of military support, countries such as Italy, Spain, the Netherlands, and Belgium either limited or stopped arms sales to Israel. This difference was already built into NATO before February 2026 but became more serious afterward.

In February 2024, a Dutch court ordered the government to stop sending parts of F-35 fighter jets to Israel. The argument came from a humanitarian perspective, stating that Israel is violating international humanitarian law with these weapons. By September 2025, Spain went a step ahead and introduced a full arms embargo on Israel, including both exporting and importing of any military goods through Spain. This policy was approved by the parliament, making it hard to reverse when the war in 2026 began. Moreover, a Belgian court ruled that the Flanders region must stop supplying arms to Israel. [15] These decisions demonstrate that NATO could legally limit arms exports even if doing so goes against the U.S. strategic objectives.

The same international humanitarian law concerns that had led to the restrictions on arms to Israel in 2024 and 2026 are now applied to this major conflict with Iran. As Trump criticized Europe’s unwillingness to support the war and contemplated pulling the U.S. out of the alliance, tensions between Washington and its NATO partners increased. However, despite this tension, Europe’s stance on arms exports did not change, given that these restrictions were based on domestic legal systems, which cannot be reversed by the United States political pressure. In the case of the war with Iran, NATO faces a key issue that supporting the U.S. strategy would require European governments to accept legal, political, and economic risks by being associated with an offensive war.

Looking ahead: NATO after the Iran war

The Iran war may not have broken NATO, but it did change the way it originally functioned. Since February 2026, several issues have exposed deeper divisions within the alliance, including a lack of consensus and the different reactions of European states to the war. These problems reflect a long-term difference in strategic objectives between the United States and European countries that had been building for years prior to the war and have become more visible during the recent war. NATO might survive the crisis, but what kind of alliance will it become afterward? The fundamental trust and ways that supported cooperation have been weakened, and this will continue to shape the relations between the United States and Europe.

One of the most important long-term effects of the war against Iran is that Europe would seriously consider moving toward strategic independence away from the United States. What was once an idea is now turning into a practical necessity. European countries are increasing their defense spending and raising their own military capabilities. Moreover, they are working to reduce the reliance on the United States in areas including trade and energy. This shift toward autonomy signals that the alliance may not be enough to guarantee Europe’s security. Thus, as an institution, NATO will remain there. However, the unity of the alliance in matters of collective military action is weakening, and cooperation is becoming increasingly conditional.

Furthermore, the United States is facing a clear challenge in how it leads the alliance. Relying on military strength alone is no longer enough to ensure that allies will follow its decisions. When European countries have different strategic priorities or face domestic legal and political limits, they are less willing to provide support. Thus, if the United States continues to act unilaterally and expects full support from its allies, it may further encourage Europe to become independent from it and reconsider the future of transatlantic relations.

Conclusion

The U.S.-Israel-Iran war has revealed a serious divide between NATO members that diplomacy managed before but could not fully resolve. This division can be traced back to when the United States withdrew from the JCPOA, and from then, the tension has increasingly grown, especially after the strikes on nuclear sites in 2025 and later the full-scale war against Iran launched by the United States. What the unilateral behavior of the United States has done is remove the uncertainty and ambiguity that were once allowed within the alliance despite internal disagreements.

Nevertheless, NATO will still maintain its institutional structure and collective defense commitments because European countries have a strong reason to preserve it. The nature of the transatlantic relations will continue, yet it will gradually change. Many European policymakers believe that the damage may be lasting, but it would not lead to a collapse of the alliance. Looking ahead, European states might re-evaluate their shared purpose and reliance on NATO and shift toward investing in independent defense capabilities. This shows that the reliance on the United States is no longer strategically secure for Europe. The future of NATO will depend on whether it adjusts to this reality by improving consultation practices and defining clearer guidelines for military action, or whether it continues without meaningful reform, allowing existing strains to persist into the next decade. 

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