NATO Strain Deepens as US Campaign Against Iran Tests Alliance Unity

The United States military campaign against Iran, which began in late February, has led to significant strain within the NATO alliance.

Overview

US President Donald Trump has criticized several allies for not providing direct military support for the operation, while European members maintain that NATO's defensive mandate does not obligate them to participate in the conflict. The crisis has prompted discussions about potential US withdrawal from NATO, changes to US force posture in Europe, and efforts by European nations to strengthen their own security frameworks. A ceasefire was reached in early April, but disagreements over securing the Strait of Hormuz continue.

Key Events Timeline

• Late February 2025: The US-Israeli military campaign against Iran commences. The US did not consult NATO allies before initiating the operation.
• March 2025: President Trump begins criticizing NATO allies for not supporting the military campaign. Iran closes the Strait of Hormuz to commercial shipping, impacting global energy prices.
• Early April 2025: A two-week ceasefire agreement between the US and Iran is reached, including provisions for reopening the Strait of Hormuz.
• April 8, 2025: NATO Secretary-General Mark Rutte meets with President Trump at the White House to discuss alliance tensions.
• June 2025: US Defense Secretary Pete Hegseth announces a six-month review of US forces in Europe at a NATO defense ministers meeting in Brussels.

US Criticisms and Positions

President Trump has repeatedly criticized NATO allies during the conflict. He has described NATO as a "paper tiger" and stated he is considering US withdrawal from the alliance. Trump told Reuters he is "absolutely without question" considering an exit and told The Telegraph the matter is "beyond reconsideration."

Specific criticisms from President Trump include:

United Kingdom: Trump stated Prime Minister Keir Starmer "took far too long" to permit US forces to use UK airbases. He commented that Starmer "has not been helpful" and stated, "This is not Winston Churchill that we're dealing with." Trump later compared Starmer to Neville Chamberlain.

Spain: Trump described Spain as a "loser" and "very hostile to NATO."

France: Trump stated that France refused to allow planes carrying military supplies for Israel to fly over its territory, calling France "VERY UNHELPFUL."

US Secretary of State Marco Rubio stated on March 31 that the US would "reexamine" its relationship with NATO, citing allies' non-assistance in the Middle East. He questioned whether the alliance serves its purpose if the US cannot utilize European military bases during conflicts.

Defense Secretary Pete Hegseth criticized European allies for denying US forces access to bases for operations against Iran, describing this as "shameful." He announced a six-month Pentagon review of American forces in Europe and called for a "NATO 3.0" with Europe taking primary responsibility for conventional defense of the continent.

An internal Pentagon email, reported by multiple sources, outlined potential measures against NATO allies perceived as uncooperative, including options for suspending Spain from the alliance and reviewing US support for the UK's claim to the Falkland Islands. A US official confirmed the email's existence and described it as a signal to NATO partners. The email did not suggest US withdrawal from NATO or closure of US bases in Europe.

UK Government Position

Prime Minister Keir Starmer has maintained that the UK will not participate in offensive operations against Iran. He stated he was not prepared to join a conflict "without a plan to get us out" and opposes "regime change from the skies."

Key UK actions and positions include:

• Initial refusal: Starmer declined to permit the US to use British bases for offensive strikes.
• Subsequent authorization: He later authorized use of UK bases for what he described as defensive actions, including targeting Iran's ballistic missiles.
• Defensive operations: UK aircrews and ground forces engaged in defensive actions. The Ministry of Defence reported that RAF gunners intercepted "multiple" Iranian drones on a specific night.
• Diego Garcia: Disagreement emerged over US military jets securing landing rights at the Diego Garcia air base. Trump questioned the UK's decision regarding sovereignty of the Chagos Archipelago, which includes Diego Garcia.
• Strait of Hormuz: Starmer announced that the UK would convene a meeting of 35 countries to explore measures for restoring access in the Strait of Hormuz. The US was reportedly not invited.
• NATO commitment: Starmer affirmed the UK's "full commitment to NATO," characterizing it as "the single most effective military alliance the world has ever seen."

Domestically, a YouGov survey indicated 60% of Britons opposed the military action, with 49% opposing and 28% supporting the US strikes on Iran according to another poll.

NATO Responses and Strains

NATO Secretary-General Statements

Mark Rutte met with President Trump at the White House on April 8. Following the meeting, Rutte acknowledged that Trump "is clearly disappointed with many NATO allies" and stated, "I can see his point." Rutte described the conversation as "very frank, very open."

Rutte defended the alliance, stating that European members are increasing defense spending and providing significant support. He noted that 4,000 to 5,000 US aircraft operated from European bases during the six-week war. He acknowledged that some allies were initially slow to provide logistical support, partly because Trump chose not to inform allies in advance to maintain operational surprise.

Rutte stated that NATO, as a defensive alliance, would not participate in the Iran conflict. He said NATO's mandate is self-defense and the alliance would not engage in conflicts outside its designated territory.

Strait of Hormuz Security

Rutte informed several European capitals that President Trump expects concrete commitments within days for assistance in securing the Strait of Hormuz. A coalition of approximately 40 countries, primarily NATO members along with Japan, South Korea, and Australia, has been working on a strategy to secure the waterway after hostilities cease.

Australia's Chief of Defence, Admiral David Johnston, confirmed the Royal Australian Navy could deploy a warship to the Strait of Hormuz if requested. German Chancellor Friedrich Merz expressed Germany's readiness to assist once a long-term ceasefire is established.

Turkish Position

Turkey's Trade Minister, Ömer Bolat, stated in an interview with Euronews that NATO allies are not "obliged" to assist the United States and Israel in the conflict with Iran. Bolat said, "NATO's presence is primarily as a deterrent force to maintain peace and security on the European continent, but also globally." He affirmed that NATO countries could remind the US that the alliance is defensive in nature and was not involved in planning the conflict.

Domestic and Allied Reactions

United Kingdom

Reactions within UK politics have been mixed:

• Nigel Farage (Reform UK) initially expressed strong support for US and Israeli operations but later focused on domestic issues like petrol prices.
• Kemi Badenoch (Conservative) initially supported US actions, later clarifying her stance was limited to assisting in missile defense.
• Andrew Mitchell (Conservative) described Starmer's initial refusal as a "very big mistake."
• Some senior Tories maintained that Starmer's refusal was a mistake, while others faced challenges maintaining a consistent stance as public sentiment shifted.

Foreign Office Minister Stephen Doughty stated, "Our relationship with the United States is strong... It has endured, it continues to endure, and it will endure into the future."

Other European Nations

• Spain: Refused to let the US use its airspace or bases for attacks on Iran. Prime Minister Pedro Sánchez stated Spain is a "reliable member" of NATO. He wrote on X that his government "will not applaud those who set the world on fire just because they show up with a bucket."
• France: Blocked Israeli military planes from its airspace. Authorities made decisions on a case-by-case basis for use of joint bases.
• Italy: The government denied US military aircraft permission to use the Sigonella air base for a Middle East-related mission. Prime Minister Giorgia Meloni stated NATO "must remain united."
• Germany: Chancellor Friedrich Merz stated Germany's desire for the US to remain in NATO and encouraged urgent talks with Iran.

NATO Withdrawal Considerations

Legal Framework

A 2024 law requires a US president to secure a two-thirds Senate majority or an act of Congress to withdraw from NATO. This provision was included in the National Defense Authorization Act for fiscal year 2024, co-sponsored by Democratic Senator Tim Kaine and then-Senator Marco Rubio. President Trump has asserted he believes he possesses executive authority to make such a decision independently.

Congressional Responses

Several Republican senators have publicly supported NATO:

• Senators Thom Tillis (R) and Jeanne Shaheen (D), co-chairs of the Senate NATO observer group, issued a joint statement highlighting NATO's support after the September 11 attacks and stating that withdrawal would undermine US national security interests.
• Senators Mitch McConnell (R) and Chris Coons (D) issued a joint statement emphasizing the sacrifices of NATO troops alongside American forces in Afghanistan and Iraq.
• Senate Minority Leader Chuck Schumer stated the Senate would not vote to leave NATO.

Russian Assessment

Dmitry Medvedev, Russia's Deputy Chairman of the Security Council, stated that President Trump is unlikely to withdraw the US from NATO, citing congressional opposition. Medvedev characterized Trump's rhetoric as "pure showmanship" but noted that limited actions by Washington, such as reducing troop presence or restricting supplies, could still affect alliance cohesion.

European Defense Developments

European governments have taken steps to strengthen their security frameworks amid uncertainty about US commitment:

Germany: Published its first military strategy since World War II, aiming to become the strongest conventional army in Europe by 2039. Germany also unveiled a defense plan identifying Russia as the main threat.

France: Opened talks with seven non-nuclear nations on extending its nuclear deterrent.

Defense spending: European NATO members increased defense spending by more than 62% between 2020 and 2025. A new spending target of 5% of GDP by 2035 was agreed at the 2024 NATO summit.

US troop presence: The Pentagon announced plans to withdraw 5,000 US service members from Germany. As of end of 2025, US active-duty troops in Europe numbered 36,436 in Germany, 12,662 in Italy, and 3,814 in Spain.

A report by the International Institute for Security Studies identified European dependencies on US capabilities in areas including deep strike capabilities, intelligence and surveillance, space-based capabilities, logistics, and integrated air and missile defense. The report estimated it could take over a decade and approximately $1 trillion to replace key US conventional military capabilities in Europe.

Expert Analysis

Jim Townsend (Center for a New American Security): "There will be no return to business as usual in NATO, during neither this US administration nor the next one. We are closer to a break than we have ever been."

Stefano Stefanini (former Italian ambassador to NATO): "He doesn't need to leave NATO to undermine it; by just saying he might, he has already eroded its credibility as an effective alliance."

Minna Alander (Swedish Institute of International Affairs): NATO could survive a US withdrawal "as European members have an incentive to maintain it, even if in a radically different form."

Ivo Daalder (former US ambassador to NATO): "Something fundamental has broken" regarding the US commitment to European security.

Jörn Fleck (Atlantic Council): Advised European leaders to "avoid getting drawn in by provocations or insinuations over NATO and Article 5."