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What and who is the Joint Expeditionary Force?

The Joint Expeditionary Force (JEF) was established in 2014 at the NATO Summit in Wales by the UK and six other countries. Announcing its formation, the UK government described it as “a pool of high readiness, adaptable forces that is designed to enhance the UK’s ability to respond rapidly, anywhere in the world, with like-minded allies, or on behalf of international organisations such as the UN or NATO”. The JEF has ten members: the UK, Denmark, Estonia, Finland, Iceland, Latvia, Lithuania, the Netherlands, Norway and Sweden. The armed forces of JEF countries hold joint exercises and ministers meet regularly at JEF Leaders’ summits.

Not part of NATO

The JEF is not part of NATO but it does intend to complement it. At a summit in October 2023 JEF leaders outlined this relationship as follows:

For all JEF Participant Nations, NATO is the foundation of collective security in the Euro-Atlantic area. The JEF, from its inception, has been designed to complement both NATO and Participant Nations’ own response capabilities. The JEF needs to be ready to respond in scenarios ranging from below the threshold of NATO’s Article 5 through to full-spectrum interventions during times of crisis or conflict, operating seamlessly with NATO.

A former Standing Joint Force Commander, Major General Jim Morris, described how “what the JEF usually does is provide a gearing in-between nations and NATO, where we can discuss issues regionally, we can react to situations on a non-consensus basis, so quickly”.

A 2021 blog post by UK Strategic Command highlighted the flexibility and potential speed of decision making and deployment as some of the advantages of the JEF. Strategic Command also pointed to the potential for JEF allies to “take collective action below the traditional threshold of war”, which it said NATO might not be able to do.

Membership

The JEF is UK-led and was initially made up of six other countries, Denmark, Estonia, Latvia, Lithuania, the Netherlands, and Norway, with the primary goal of protecting northern Europe. Finland and Sweden joined the JEF in 2017 and most recently Iceland joined in 2021, bringing the current total of JEF nations to ten. The addition of then non-NATO members Finland and Sweden gave the JEF a broader reach across northern Europe. Finland and Sweden have subsequently joined NATO in 2023 and 2024 respectively. 

Canada has applied to join the JEF, Prime Minister Mark Carney announced on 16 September 2026.

UK operational lead

The UK is the “framework” or lead nation of the alliance. UK operational command of the JEF is led by Standing Joint Force Headquarters (SJFHQ) in London. Information on JEF activities are provided by SJFHQ on the Joint Expeditionary Force website.

What does the JEF do?

The JEF is not a separate army or fighting force. Rather, it is a collection of units who train and exercise together. It also provides a forum for discussion of defence and security issues between allies. There is an “opt-in” approach which means that as long as two or more JEF members agree to work together, then an exercise can go ahead, with subsequent agreement of the practicalities.

The JEF’s geographic focus is the Arctic and High North, North Atlantic and the Baltic Sea region.

The JEF vision, agreed by leaders of JEF nations in October 2023, stated that Russia’s invasion of Ukraine has increased the importance of JEF as “enablers of regional security” for its members. The 2025 Strategic Defence Review described Russia as an “an immediate and pressing threat”. At a meeting in October 2026, JEF defence ministers said “JEF nations do not seek confrontation and pose no threat to Russia, but Russia should be in no doubt that we will defend ourselves”.

Military exercises

In 2019 nine JEF nations took part in Baltic Protector, the JEF’s first training deployment. The exercise involved 20 ships and around 3,000 personnel, culminating in practice amphibious landings in Europe’s Baltic states.

In October 2023 then Prime Minister, Rishi Sunak, promised to “step up” the UK’s presence in northern Europe, committing to sending more than 20,000 service personnel to the region in 2024 on exercises, training and operational deployments.

JEF exercises have also been coordinated with NATO exercises. For example, in February 2024 a JEF air defence exercise, Global Guardian, was coordinated with NATO’s steadfast defender exercise.

The UK’s SJFHQ has hinted that exercises are held with Russia in mind. In a press release on Operation Global Guardian in 2024, they highlighted how such exercises “are important for sending a clear message that deter malign activity and reassure friends”.

During 2023 the JEF has developed a series of “Response Options”, which it said are “designed to deter, and defend our region from threats and establish how quickly we can respond to crises”.

The JEF website provides more information on JEF activities and exercises.

Flagship exercise: Lion Protector

In August 2026, JEF nations launched what it described as a “new series of annual, multi-national military readiness exercises” to “rehearse and refine” the response options. The UK described JEF response options as “pre-agreed, scalable military response packages… bringing to bear multi-domain force to support rapid and coordinated responses to emerging crises and security challenges”. Exercise Lion Protector 26 ran until October 2026 and Ukraine participated for the first time.

Defending critical national infrastructure

In October 2023 JEF leaders agreed at a summit in Sweden to deepen cooperation on protecting critical national infrastructure. Critical national infrastructure includes undersea communication cables and energy pipelines; in 2022 the Nord Stream pipelines in the Baltic Sea were sabotaged, highlighting the potential vulnerability of undersea cables and pipelines to malicious attack.

In November 2023, the JEF Defence Ministers agreed to activate for the first time a JEF response option, enabling maritime and air capabilities to be deployed to protect critical undersea infrastructure across the JEF’s core region.

A second response option took place throughout June 2024, monitoring shipping, undersea energy and communication routes and suspicious activity. It was led from SJFHQ in London, using a total of 28 ships and six aircraft from JEF nations.

In January 2025, JEF nations activated a UK-led reaction system to “track potential threats to undersea infrastructure and monitor the Russian shadow fleet”. ‘Nordic Warden’ uses AI (artificial intelligence) to assess data from a range of sources to “calculate the risk posed by each vessel entering areas of interest”. The Ministry of Defence said there were 22 areas of interest being monitored, including parts of the English Channel. The announcement followed damage to EstLink 2, a major undersea cable in the Baltic Sea connecting Finland and Estonia  in December 2024.

Summits and defence ministerial meetings

There are regular leadership and defence ministerial meetings of JEF nations. Below are links to UK Government press releases of meetings in 2026:

The next leaders’ summit will be held in Iceland in spring 2027.

JEF-Ukraine Enhanced Membership

In October 2023 JEF leaders agreed to invite Ukraine to observe JEF exercises during 2024 and 2025. Their presence was intended to “increase interoperability, and enhance the capability of the Armed Forces of Ukraine”.

Boris Johnson, when Prime Minister, observed that JEF allies’ had similar outlooks and stated that the JEF “consists of the countries that were fastest off the block, with us, in sending direct military assistance to Ukraine”.

In November 2025, JEF Defence Ministers announced the formation of an enhanced partnership with Ukraine. The UK Government said that, among other things, JEF forces would provide training for the Ukrainian armed forces, and “closer collaboration on protection of critical underwater infrastructure, drones, battlefield medicine, and methods for countering disinformation”.

JEF Defence Ministers agreed to “Reinforcing steadfast support to Ukraine through ambitious delivery of the JEF-Ukraine Enhanced Partnership” in October 2026. Defence Ministers “agreed to deepen Ukraine’s involvement in JEF activities”.

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