BJEF – A Joint Expeditionary Force for the Balkans

At the 2014 Wales Summit, the UK country spearheaded the formation of a multi-national military partnership – the Joint Expeditionary Force (JEF). The announcement elicited only a moderate degree of attention and reaction at the time. But more than a decade later, it has proven to be a remarkable and surprising success in keeping the peace in Northern Europe.

An often overlooked but strategically vital part of Europe – the Western Balkans – now stands at a critical turning-point. Decades of peacebuilding risk being undermined by secessionism and increasingly militant local nationalisms, both emboldened by Russian interference.

Croatia, Slovenia, Montenegro, North Macedonia, and Albania are in NATO – but as long as Bosnia and Kosovo remain outside of the Alliance, they will remain deeply vulnerable to external interference. In the absence of their membership in the trans-Atlantic community, these two countries have remained the prime target of Serbian and Russian meddling in recent years. This could cascade into greater instability, and even warfare, in the Balkans.

This situation can be changed by thinking outside the box.

The Origins of the JEF

The origins of the Joint Expeditionary Force (JEF) date back to 2010, when the UK Ministry of Defence established the Northern Group concept. The Northern Group includes the five Nordic countries, the three Baltic states, as well as Poland, Germany, and the Netherlands. Three main factors motivated the creation of this grouping.

First, the UK is a Northern European country with corresponding security interests. At the time, much of the strategic focus was on counterinsurgency operations in Iraq and Afghanistan. As a result, British policymakers appeared to lose sight of the enduring threat posed by Russia, and London’s broader role in European security. The 2010 Strategic Defence and Security Review placed an emphasis on boosting ‘Alliances and Partnerships,’ stating that the UK should seek ‘new models of practical bilateral defence and security co-operation with a range of allies and partners.’ As a key power in the region, the UK had both the interest and the responsibility to assume a more proactive leadership role in Northern Europe.

Second, Northern Europe needed greater co-ordination and co-operation on security matters. There was significant overlap and fragmentation among the various existing regional security arrangements. For example, in 2010, Finland and Sweden were members of the European Union but not of NATO. Norway was a NATO member but not part of the EU. Denmark was in both the EU and NATO, but had a special opt-out from the EU’s Common Security and Defence Policy (CSDP). The Northern Group demonstrated that traditional diplomacy and multilateral engagement could still enhance regional security – defence co-operation need not be confined to or directed by large institutional frameworks like NATO or the EU.

Finally, the creation of a multinational security platform in Northern Europe served a domestic political purpose. It allowed Conservative ministers in the coalition government with the Liberal Democrats to show that scepticism toward Brussels was not synonymous with being ‘anti-European.’ At a time when Euroscepticism was beginning to rise in the UK, initiatives like the Northern Group helped communicate that London was not abandoning Europe – even as debates about the UK’s relationship with the EU intensified.

These developments eventually led to the establishment of the JEF in 2014. For the Nordic and Baltic states, the JEF has become a flexible, predictable and capable source of deterrence in Northern Europe. This 10,000-strong force – 'committed to upholding peace, stability, and international law’ – has consistently punched above its weight. Rather than undermining existing defence efforts, the JEF has complemented them, helping to turn the ambitious goals of the Nordic Defence Co-operation (NORDEFCO) into a reality.

The JEF has demonstrated its ability to address today’s most pressing geopolitical challenges. It has been a steadfast supporter of Ukraine, and there have been growing calls from key officials and ministers to invite Ukraine to participate in the future. The JEF could also play a constructive role in any future ceasefire or post-war security arrangement between Ukraine and Russia. Ukrainian President Volodymyr Zelenskyy has praised the JEF’s support, attending a JEF summit and urging its members to ‘help yourselves by helping us.’

The durability and popularity of JEF is a testimony to its success. It has even been touted as a model for addressing wider Indo-Pacific theatre and emerging global security issues more broadly.

BJEF is Needed

There is another region that also requires a more focused UK role: the Balkans.

Many of the same factors that prompted the creation of the Northern Group and the Joint Expeditionary Force (JEF) also apply to the UK’s approach to the Balkans and support the case for establishing a Balkans Joint Expeditionary Force (BJEF) led by the UK and including the seven Balkans countries of Albania, Bosnia-Herzegovina, Kosovo, Montenegro, North Macedonia and Slovenia (Henceforth, the BJEF-7).

Firstly, Britain has a long historical involvement in the region dating back to the 19th century. More recent history – whether the events of 1914 or the wars of the 1990s – demonstrates that instability in the Balkans often reverberates across Europe, including the UK. While the UK is not itself a Balkan country, it can act like a Balkan power, as the region remains closely tied to Britain’s security and broader strategic interests.

Secondly, as in Northern Europe, the Balkans comprise a complex patchwork of overlapping security and organisational affiliations. Croatia and Slovenia are members of both NATO and the EU. Montenegro, North Macedonia, and Albania are in NATO but not the EU. Bosnia and Herzegovina is in neither but is a candidate for NATO membership and hosts the EU’s largest military operation through EUFOR. Kosovo – while not recognised by all NATO and EU member states – strives for deeper integration with the Euro-Atlantic community and currently hosts NATO’s largest ongoing military operation through KFOR. Despite this fragmented institutional landscape, the countries of the region face shared security challenges. The UK is well positioned to serve as a framework nation and convening power for a JEF-style force in the Balkans.

Finally, there is a domestic political incentive for London to act. The UK has been a leading European power for centuries, and this will continue regardless of its EU membership status. Moreover, the Labour Party was recently elected on a platform that included a commitment to establish a new security relationship with the European Union. Focusing UK-EU defence cooperation on the Balkans would be an ideal way to build confidence between London and Brussels – while also demonstrating to Washington that Europe is willing to shoulder a greater share of the security burden.

Geopolitical and Security Challenges in the Balkans

Thirty years after the Dayton Peace Agreement brought an end to the Bosnian War, the Balkans remain an area of unfinished business for Euro-Atlantic integration and continue to represent a source of instability in the continent’s immediate neighbourhood. Aside from Ukraine, it is Europe’s most persistent geopolitical challenge. Following the violent wars of the 1990s that accompanied the dissolution of Yugoslavia, Europe and the United States helped stabilise the region through sustained peacekeeping and diplomatic engagement.

However, times have changed. With the US and Europe unwilling or unable to engage meaningfully in the Balkans, a deep power vacuum has emerged in the region that outside actors like Russia and China are rushing to fill. The challenges in the Balkans are threefold.

First, the past risks repeating itself if the West/Britain fails to learn its lessons. Serbia is where Russia was in 2014, intoxicated by historical grievances, anti-Western sentiment, and engaging in ‘wolf-warrior’ diplomacy. Unfortunately, the EU, US and UK have met this sabre-rattling with equivocation and weakness. Seeing Serbia’s success with this approach, others have increasingly followed their lead, including Croatia and Hungary, who now routinely interfere in the domestic politics of Bosnia and Kosovo. (NB: Croatia has excellent links to Kosovo, mainly due to Kosovo being seen as a counterbalance to Serbia).

Secondly, Serbia has matched such rhetoric with action – the ‘Serbian World’ agenda is in full swing, inspired by Slobodan Milosevic’s ‘Greater Serbia’. President Vucic has been called ‘The Political Son of Milosevic’ and has taken Serbia down an increasingly illiberal and irredentist path. Serbian rearmament, the planned introduction of conscription, and the illegal deployment of troops to the Kosovan border are no accidents – they are part of this broader strategy.

Thirdly, across the Balkans, with the exception of KFOR, there is no credible and effective deterrence to meet this challenge. EUFOR has been hollowed out, and the lack of a robust NATO and EU commitment to the region has created a power vacuum which adversaries have exploited.

Russia has fuelled and embraced the rising discord in the region. Russia has provided extensive political, economic, and diplomatic support to Serbia and secessionists in Bosnia’s Republika Srpska entity. The Russian Ambassador even remarked that ’In the case of practical rapprochement of Bosnia and Herzegovina and NATO, our country will have to react to this hostile act’. Yet the vast majority of Bosnians – including a significant minority of Bosnian Serbs – support NATO membership, and the 2005 ‘Law on Defence’ clearly stated the ambition to join NATO, and committed officials to prepare the country’s legal architecture for the same.

In addition, Russia continues to block international recognition of Kosovo, to embolden secessionists in the Republic Srpska entity, while seeking to expand their ‘near monopoly on the oil and gas market’ in the region. Russian sympathizers in Bosnia’s Croat nationalist HDZ also continue to block the country’s decoupling from Russian gas. Moscow’s ‘War on Truth’ disinformation campaigns, spearheaded by state-backed media forces such as RT and Sputnik, have also fuelled the rising anti-Western sentiment in the region.

This could escalate into armed conflict if the situation deteriorates much further. Successive rounds of armed clashes in Kosovo and acts of state-backed sabotage are major red flags.

Benefits and Challenges of a BJEF

As a result – a Balkan Joint Expeditionary Force (BJE) may just be the ‘Game-Changer’ the region needs in a time when the peace, 30 years later, seems to be unravelling.

A BJEF could bring the unity, stability and security the region deserves and needs.

• Improving regional interoperability. A Balkans Joint Expeditionary Force (BJEF) would enhance interoperability among participating forces and deepen the region’s integration with the institutions of the democratic world. It would help place the Western Balkan countries firmly on the path toward Euro-Atlantic integration, supporting their eventual membership in NATO and the EU. British forces could serve as the framework nation and provide training, mentoring and assistance to local forces, as they already do under existing initiatives.
   
• Expanding Operation CHELONIA. The UK could use the BJEF framework to scale-up and broaden the scope of Operation CHELONIA, its current defence cooperation initiative in the Balkans.
   
• Establishing a standing coordination mechanism. The BJEF would institutionalise UK-Balkan defence coordination, leading to annual BJEF ministerial meetings and CHOD-level (Chiefs of Defence) engagements. Between summits, UK officials would regularly consult and coordinate with their BJEF-7 counterparts to ensure strategic alignment and operational readiness.
   
• Improving regional military capability. By standardising training, facilitating joint exercises, and promoting doctrinal alignment, the BJEF would strengthen the military effectiveness of participating countries.
   
• Operational flexibility. Unlike NATO or EU CSDP missions, the BJEF would not require unanimity to initiate operations. As with the JEF, the United Kingdom would act as the framework nation and, following consultation, could launch operations with any combination of participating members. Each BJEF-7 state would retain full sovereign authority over whether or not to contribute forces.
   
• Expanding options for policymakers. Like the JEF, the BJEF could serve both as a deterrent and a rapid-response mechanism. It would train for, and when necessary, conduct localised operations across the region, such as:
   
  • In Bosnia and Herzegovina, it could reinforce EUFOR-Althea in deterring secessionist threats from the entity of Republika Srpska or establish a permanent presence in the strategically critical Brčko corridor.
     
  • In Kosovo, the BJEF could augment KFOR to deter aggression and support the security of Serb-majority municipalities in the north. It could work alongside local security services in joint patrols and border control missions to combat organised crime and smuggling.
     
  • In the event of natural disasters, the BJEF could also provide emergency relief, including search and rescue operations.
     
• Giving Britain a stake in Balkan security. The UK would serve as the ‘organiser-in-chief’ of the BJEF, with regional partners contributing the bulk of the personnel. The UK would provide planning, command and control, special forces capabilities, logistics, and the institutional knowledge gained from its leadership of the JEF. Albania and Bosnia and Herzegovina, due to their relatively larger armed forces, would likely be the main troop contributors, with Kosovo rapidly developing its own capabilities.
   
• Enhance burden sharing within the transatlantic alliance. President Trump and his senior officials have consistently highlighted the imbalance in transatlantic defence contributions. Greater British involvement in the Balkans – particularly through the creation of a BJEF – would serve as a clear example of a European-led solution to a European security challenge. Such a move would undoubtedly be well received by the White House as a demonstration of increased European responsibility in regional defence.
   
• Give the UK more leverage. A UK led BJEF would enhance London’s leverage in regional talks and negotiations, sending a clear signal of resolve and strength to autocrats like Vucic and Putin. For example, a decisive show of strength, such as the mobilisation of the BJEF may be sufficient to deter them from aggressive policies.

Make no mistake, even with the many opportunities that the creation of a BJEF could have on the region, this initiative is not without its challenges. Several obstacles would need to be addressed:

• Limited resources among regional states. Collectively, the BJEF-7 countries spent approximately $4.1 billion on defence in 2024, according to NATO’s official data releases for NATO members and World Bank estimates for Bosnia and Kosovo. For comparison, Sweden – a single JEF member – spent roughly three times that amount in the same year. Only four of the BJEF-7 (Kosovo, Albania, North Macedonia, and Montenegro) met or slightly exceeded NATO’s 2% of GDP defence spending benchmark.
   
• Enduring regional mistrust. The historical and contemporary tensions between the Western Balkan nations make it a challenge to bring these nations together in a common cause. However, a bias-free neutral framework combined with mission clarity will ensure that BJEF operates as a force to heal, not exacerbate, existing tensions. A key example is the relationship between Bosnia and Herzegovina and Croatia. Croatia’s involvement, particularly its political support for Bosnian Croat leaders seeking greater autonomy or the creation of a separate entity within Bosnia and Herzegovina has, at times, complicated Bosnia’s internal stability and efforts at unity. Addressing such sensitivities with balance and care is essential for building regional cooperation.
   
• Non-recognition of Kosovo. Bosnia and Herzegovina does not formally recognise Kosovo’s independence. While this complicates Kosovo’s full participation in the BJEF, it does not render it impossible – particularly if pragmatic and inclusive policies are pursued.
   
• Resource constraints in the UK. Successive British governments have underinvested in defence. Nonetheless, the geopolitical benefits of serving as the BJEF framework nation would far outweigh the modest financial burden. For context, since 2023 the UK has allocated only £1.19 million to the JEF – an affordable investment relative to the strategic value returned.
   
• Russian misinformation. As with any significant NATO or European military deployment or training exercise, Russian disinformation efforts will seek to undermine the legitimacy of the mission and sow distrust among local populations. The UK must proactively counter this by developing a clear public engagement strategy that explains the purpose of the BJEF, its activities, and the benefits it brings to regional stability.
   
• Understand that the BJEF is not a silver bullet. The Balkans region faces many challenges unrelated to security. Rampant corruption and stagnant economic activity are exacerbated by a lack of energy security and sectarian divisions. The BJEF should be considered a tool in the UK’s Balkan toolbox, but it must be one part of a larger strategy that London should take towards the region.

The challenging situation in the Western Balkans is a security issue – demanding a security response – grounded in firm clarity and decisive action. With this in mind, there are three pressing challenges facing the region.

The British Role 

Britain ought to take this seriously and urgently. Indeed, globally there are now the highest number of active conflicts than at any point since the Second World War. MI5 recently warned of ‘mayhem in our streets’ due to covert, and overt, Russian action.

Britain has taken a more active approach to the Western Balkans, as embodied by the recent Operation Chelonia training exercises and the signing of new deals to tackle smuggling gangs are most welcome. It has also provided critically needed training to the Bosnian Armed Forces in recent years, increasing their NATO interoperability capacities.

Britain has the means and resources to organise and promote BJEF, supporting the force from its bases in Cyprus and Gibraltar. As the UK seeks to fulfil our post-Brexit ‘Global Britain’ ambitions, there are few better ways to signal its commitment to deterrence. There are also facilities in Bosnia and Kosovo that could be easily re-operationalized for these purposes, in addition to NATO facilities in Albania, Montenegro, and North Macedonia.

Conclusion

On the sidelines of the UK-hosted Berlin Process Summit in October, the UK should convene an initial meeting of the BJEF-7 countries. This should be followed by technical consultations at the official level, leading to the signing of a Letter of Intent, a Foundational Memorandum of Understanding, and ultimately a Comprehensive Memorandum of Understanding. The Comprehensive MoU would provide the strategic context and formalise the operational framework within which the BJEF would function.

The Trump administration has made it clear that the Europeans must step up ‘Burden-Sharing’, and not rely on American resources and troops, as their geopolitical focus shifts further to the Indo-Pacific. The creation of the BJEF could be the first step in this direction.

Now is the time to show firm leadership and clear resolve. An EU-UK defence pact is welcome, and the Western Balkans ought to play an important role when European security is considered.

The rapid reaction capabilities and the flexibility of the BJEF would be an essential tool to act not only to deal with crises quickly and effectively – but also to deter them. If such a force had existed and been employed in Bosnia and Kosovo in the 1990s, countless lives could have been saved, and the region’s political stability would certainly be in far better shape.

The UK can either ignore the problem and deem it to be beyond its immediate concern and interest because the Balkans are more than 1,000 miles away, or policymakers can deal with an even greater problem later on. If conflict did break out, another refugee and energy crisis would once again sweep Europe.

Recall, Putin moved on Ukraine first in 2014, and then again in 2022. Years of Western appeasement, the rollback of military commitments, and the inadequate sanctions regimes emboldened Moscow. The UK risks repeating the same mistakes in the Western Balkans.

Also, the UK has a responsibility to the region, to the soldiers who served and to those who do not wish to see decades of peacebuilding and reconciliation abandoned. From the Baltics to the Nordics to Ukraine to Hong Kong, the British Government has shown admirable leadership and moral clarity in recent years.

The UK ought to take the initiative once again to prevent our continent from sleepwalking into conflict once again. The challenge in the Balkans, due to the lack of deterrence, the rise of Serbia, and the spectre of Russia, risks escalating into a full-blown crisis.

This would be a much more efficient, organised, and powerful force than the existing haphazard and fragmented arrangements. And it would help to bring unity and hope to the region.

A force centred around the use of rapid reaction, pooled resources and cutting-edge technology – but guided by the timeless principles of unity, peacekeeping and collective security, will blend the old with the new to create a power fit for the challenges of the time.

The price of pre-emptive action is always much cheaper than the price of apathy and abandonment. But if the UK opts for the latter, it won’t be just the Balkans which will suffer as a result.

© Arminka Helic and Luke Coffey, 2025, published by RUSI with permission of the authors.

The views expressed in this Commentary are the authors', and do not represent those of RUSI or any other institution.

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