EU moves to activate mutual defence clause amid NATO uncertainty

The European Union is preparing to clarify how its mutual defence mechanism can be used, as officials work to raise the profile of a little-known clause often overshadowed by NATO’s widely recognised Article 5.

In an effort to strengthen its strategic autonomy amid growing uncertainty over transatlantic security guarantees, the EU’s diplomatic arm, the European External Action Service (EEAS), is drafting a practical guide to help member states understand when and how to invoke Article 42.7 of the Lisbon Treaty, Euractiv reports.

Several diplomats and officials told Euractiv that the planned manual would outline “what kind of resources are available from the EU if the A42.7 mechanism is triggered when country is threatened.” The document is expected to provide clarity on capabilities and procedures that remain poorly defined.

According to sources familiar with the discussions, EU delegations are set to conduct a bureaucratic simulation exercise as early as May to help shape the final guidance. The exercise will test how member states might respond to different crisis scenarios.

Two officials, speaking on condition of anonymity, said the manual would likely cover three distinct situations: one involving NATO’s mutual defence clause, one centred on the EU’s Article 42.7, and a third scenario in which both mechanisms could apply simultaneously.

A third source confirmed that preparations are also underway for a discussion among EU ambassadors, as part of broader efforts to refine the bloc’s collective response tools.

Interest in the EU’s mutual assistance clause has resurfaced following recent security concerns, including incidents in which Iranian drones targeted Cyprus. The episode prompted renewed debate among diplomats about how the clause can be operationalised in practice.

Three EU diplomats said the EEAS is now seeking to move into an “implementation phase,” although no clear timeline has been established. As part of the process, member states may be asked to participate in simulations where they assess whether Article 42.7 applies in various hypothetical scenarios.

The clause obliges EU countries to assist a member state under threat, but its scope remains ambiguous. Article 42.7 “requires EU countries to come to the member states in need,” yet what form that assistance should take has not been fully defined.

Nikos Christodoulides said two weeks ago that he wants to place the operationalisation of Article 42.7 on the agenda of the next EU leaders’ meeting later this month. Cyprus—one of four EU member states outside NATO—did not formally invoke the clause following the drone incident. Instead, several European countries provided bilateral military support to bolster the island’s defences.

Christodoulides noted that the situation had effectively tested the mechanism, giving the clause “flesh and bones.”

The renewed focus on EU defence tools comes as Donald Trump has repeatedly questioned the relevance of NATO’s Article 5, including earlier this week after Spain closed its airspace to aircraft involved in US and Israeli strikes against Iran.

To date, Article 42.7 has been invoked only once. France triggered the clause in 2015 following the Paris terrorist attacks, seeking to redeploy military resources from overseas operations. EU partners responded primarily with logistical assistance, including intelligence sharing, police cooperation, and counter-terrorism expertise from countries such as Belgium and Germany.

Alongside this initiative, the EEAS is drafting a new EU Security Strategy, which will include a threat assessment, a joint communication outlining the bloc’s security policy, and a roadmap for implementation. It remains unclear whether the strategy will explicitly incorporate provisions related to the mutual assistance clause.

By Vafa Guliyeva