The Joint Expeditionary Force (JEF) is in the midst of Exercise Tarassis, described as the most ambitious live activity undertaken by the coalition since its creation at the NATO Summit in 2014.
Running from early September until the end of October, Tarassis involves thousands of troops, sailors and aircrew, as well as dozens of ships and aircraft, operating from the Arctic Circle to the Baltic Sea.
The MOD stated that the exercise is designed to demonstrate the JEF’s ability to “act collectively and project power in response to a threat to regional security”.
The UK, acting as framework nation, is coordinating Tarassis through the Standing Joint Force Headquarters near London. All ten JEF nations, Denmark, Estonia, Finland, Iceland, Latvia, Lithuania, the Netherlands, Norway, and Sweden, are participating, alongside Canadian forces.
Tarassis is structured around practical defence challenges such as protecting an airfield, patrolling vital sea lanes, and reinforcing a partner nation under pressure. The exercise is also intended to illustrate how the JEF complements NATO deterrence and reassurance activities in both peacetime and crisis.
Official communications have described Tarassis as a “step change in Northern European defence cooperation”. The MOD also highlighted that it is “truly multi-national and multi-domain”, incorporating land, sea, air, space, and cyber elements.
The exercise interacts with NATO drills in the region, with the organisation noting that this demonstrates the JEF’s ability both to act independently and to integrate with the Alliance when required.
One of the early highlights included RFA Lyme Bay conducting a cross-decking exercise with 40 Commando Royal Marines in their Commando Raiding Craft. This event was cited as a clear example of how UK forces are contributing to the coalition’s maritime and amphibious capabilities.
Spanning the North Atlantic, Scandinavia, and the Baltic Sea region, Tarassis represents the latest in a series of large-scale activities undertaken by the JEF since Russia’s full-scale invasion of Ukraine in 2022. The coalition was established in 2014 as a flexible, high-readiness grouping of like-minded northern European nations and has steadily expanded its scope.
The UK described the ongoing series of activities as a demonstration of “the unity, power and reach of partner nations defending peace and security in northern Europe”.
