UK-led high north exercise demonstrates joint commitment to European and NATO security

• A UK-led effort in the High North and Baltic, involving all 10 JEF nations as well as Germany and Canada, has concluded, marking the most significant Joint Expeditionary Force (JEF) exercise in its history.
• Thousands of troops and dozens of vessels, vehicles and aircraft took part in Exercise Tarassis over two months.
• JEF activity across NATO's northern flank showcases collective regional strength and reinforces commitment to keeping Britain secure at home and strong abroad.

Tarassis, the JEF's largest and most significant military activity in its 11-year history, has successfully concluded after two months of intensive operations across the Nordic-Baltic region. By demonstrating the UK's leadership in JEF and the ability to rapidly deploy alongside allies, this activity reinforces the national security foundations as outlined in the Government's Plan for Change.   

Tarassis, which took place throughout September and October 2025, saw more than 1,000 personnel from all three services of the UK Armed Forces, with dozens of vessels, aircraft and land elements, demonstrate their collective unity, purpose, reach and capabilities.   

The deployment featured a comprehensive series of multinational military activities and engagements designed to test scenarios across the High North and Baltic Sea regions.  

Brand new technologies like Asgard, a pioneering digital targeting web, and various drones and Uncrewed Ground Vehicles (UGV) were also deployed during the activity. As set out in the Strategic Defence Review in June, more than £1 billion is being invested in pioneering ‘Digital Targeting Web' to spearhead battlefield engagements, applying lessons learnt from Ukraine to the UK Armed Forces. 

Minister for the Armed Forces Alistair Carns said:  

“Tarassis has demonstrated the UK's unwavering commitment to European and NATO security and the strength of our Alliance.   

“This landmark activity reinforces our Plan for Change and proves that together we are stronger, more capable and better prepared to meet the security challenges of today and tomorrow.”  

A key component of Tarassis was the JEF Advance Force Assistance and Theatre Enablement activity conducted in Latvia, which showcased the force's ability to rapidly reinforce frontline participant nations with highly trained and equipped military capabilities.  

Specialist infantry worked alongside combat engineers and logisticians to enhance defensive positions and secure key terrain, whilst air mobility and maritime combat power provided crucial support.  

The activity demonstrated the JEF's short decision-making timelines and capacity to rapidly deploy forces to enhance a nation's defences and deter aggression. The JEF comprises ten like-minded nations: Denmark, Estonia, Finland, Iceland, Latvia, Lithuania, the Netherlands, Norway, Sweden and the United Kingdom as the Framework Nation. 
 

By design, the JEF is a high-readiness, adaptable force that enhances the grouping's ability to respond rapidly to threats to peace and stability in northern Europe. Through planning, executing and communicating military activities across all domains during Tarassis, the JEF has made a significant contribution to European and Transatlantic security.