An alliance needs reciprocity to survive. When one partner carries an exceptional share of the responsibility for collective security, the others should be prepared to offer meaningful support when that partner needs them.
That is the principle NATO allies and European partners should apply to President Trump’s war effort against Iran. Europe has depended on American military power for generations. Its response to Washington should reflect that history.
The scale of America’s contribution is substantial. According to the UK Government’s international defence expenditure bulletin, the United States accounted for 64 per cent of NATO members’ combined defence spending in 2024. That represents national military expenditure, rather than America paying that proportion of NATO’s shared institutional budget, but it demonstrates the enormous imbalance in resources underpinning the alliance. Source: UK Government.
American forces, intelligence, logistics and nuclear deterrence have helped make European security possible. That commitment serves American interests too. Nevertheless, Europeans should recognise what it means to have a powerful ally willing to commit people, equipment and money to their defence.
For too long, European political debate has treated the continuation of that commitment as something close to an entitlement. Washington is expected to remain engaged whenever Europe faces danger, while American requests for assistance can be dismissed as somebody else’s problem.
That attitude will eventually corrode the relationship on which European security depends.
Reciprocity must mean something
President Trump is entitled to expect allies to take American security concerns seriously. European governments do not have to share every aspect of his politics to recognise the responsibilities of partnership.
The current conflict with Iran presents a test of that principle. Reporting this week indicates that the war remains unresolved, with an American naval blockade continuing and the possibility of further strikes. Europe therefore faces an immediate choice about the assistance it is prepared to offer. Source: Axios.
My view is that European allies owe Trump meaningful support as the president leading America through this conflict. That obligation arises from the alliance and the American commitment behind it. It should translate into serious discussions about practical contributions, followed by action.
Support could include intelligence sharing, defensive deployments, logistical assistance and measures to protect shipping and civilian infrastructure. Where military participation is proposed, governments should assess its purpose, legal basis and likely consequences. They should approach those decisions with a presumption that helping an ally matters.
A European government that declines a particular operation should still be able to explain what useful assistance it will provide.
Europe deserves credit—and must do more
European contributions should be acknowledged honestly. NATO reports that European allies and Canada increased their combined defence investment from 1.4 per cent of GDP in 2014 to 2.3 per cent in 2025. That is substantial progress. Source: NATO.
But increased spending also strengthens the expectation that Europe can assume greater responsibility. More capable allies should be better placed to support American operations, protect shared interests and relieve pressure elsewhere.
One valuable contribution would be taking on more of Europe’s own defence while American resources are committed to the Middle East. Greater readiness, stronger air defence and sustained support for Ukraine would demonstrate that European solidarity has practical weight.
The objective should be a partnership in which Washington can depend on European capability as confidently as European capitals have depended on American power.
Support requires a clear purpose
There is a serious objection to the argument from obligation: past assistance cannot make every future military decision correct. That objection deserves an answer.
An alliance cannot function as an unlimited authorisation for war. European governments retain responsibility for their own forces and citizens. They should seek clear American objectives, credible civilian protections and a realistic account of how military pressure will produce a durable settlement.
NATO itself explains that contributions to operations are generally voluntary, with different expectations applying to collective defence under Article 5. The case for supporting Trump over Iran is therefore a political and strategic argument, rather than an automatic treaty requirement. Source: NATO.
Those qualifications make responsible support possible. Allies can help shape strategy, press for achievable objectives and contribute to a successful outcome. Engagement gives Europe a stronger opportunity to influence American decisions than standing aside and issuing criticism.
The Iranian people must also remain central to that judgement. Any support should be directed towards defined security objectives, with civilian protection and an eventual diplomatic settlement built into the approach.
A partnership worth sustaining
Europe has a profound interest in an America that remains committed to its allies. Sustaining that commitment requires Europeans to show that the relationship works in both directions.
President Trump should be able to see practical evidence that America’s decades of support count for something when his administration asks for help. European leaders should put forward credible contributions, explain them to their publics and accept an appropriate share of the responsibility.
The transatlantic alliance has endured because its members have understood that their security is connected. Europe should act on that understanding now and stand alongside America with meaningful, considered support for Trump’s effort against Iran.
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