OSW Commentary

Military exercises on NATO’s north-eastern flank. Moving towards intensification and synchronisation

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2023 was a landmark year in terms of the scale and intensity of international military exercises among the countries on NATO’s north-eastern flank, as well as the coordination between these exercises. This was a culmination of the process that started after 2014, when NATO member states committed to changing the nature of their drills to reflect collective defence scenarios. The largest exercises held by individual countries on the north-eastern flank became increasingly interconnected, with increased participation by Western allies. The establishment of NATO battlegroups in Poland, Lithuania, Latvia and Estonia in 2016 led to the launch of several smaller exercises. Along with the rotation of US armoured brigade combat teams on the eastern flank, these forces became regular participants in such exercises. The US also began to organise its own large-scale military drills in the region. This development and harmonisation of military exercises slowed down after 2020: in 2020–2021 due to the COVID-19 pandemic, and then in 2022 as a result of the Russian invasion of Ukraine, which prompted the deployment of additional troops to secure the eastern flank. However, 2023 saw the intensification and far-reaching synchronisation of Swedish, Polish and US exercises. The approval of NATO’s regional defence plans in 2023 should further introduce a qualitative change in the programme and nature of NATO drills, which should reflect allied planning for the north-eastern flank.

NATO and US exercises on the eastern flank before 2023

Prior to 2014, NATO’s exercises were primarily focused on enhancing crisis management capabilities; only after Russia’s annexation of Crimea did their focuse gradually shift to collective defence. Separator capabilities and components (land, sea, air, special forces) of the NATO Response Force (NRF) began to be trained through a number of smaller military exercises. Noble Jump was one of the most important of these from the perspective of the eastern flank. These drills were held every two years (starting in 2015) and tested the ability of the land component of the Very High Readiness Joint Task Force (VJTF, numbering around 4000–5000 troops) to redeploy to the eastern flank. However, the first major exercises of the entire NRF with a collective defence scenario did not take place until the autumn of 2018 in Norway. The  Trident Juncture 2018 involved some 50,000 troops.[1] The deployment of NATO battlegroups Poland and the Baltic states in January 2017 led to the launch of a whole range of smaller-scale exercises which tested the ability of NATO battlegroups to conduct various types of operations.

2010 marked the beginning of regular exercises of US Army units and sub-units on NATO’s eastern flank with the launch of the annual Saber Strike drills in the Baltic states. Since then, these exercises have undergone a complete transformation: from focusing on preparing soldiers from these countries for the ISAF (International Security Assistance Force) Operation in Afghanistan to collective defence of the eastern flank. Between 2014 and 2018, they became the largest US  military exercises in the Nordic-Baltic region, involving some 2000 troops from 14 countries in 2010, 4700 soldiers from 10 countries in 2014, and up to 18,000 soldiers from 19 countries in 2018. The Saber Strike exercise did not take place in 2019 as their formula changed from annual to biennial; in 2020 and 2021, they were cancelled due to the pandemic. In 2022, they started just four days after Russia launched its full-scale invasion of Ukraine and included 13,000 troops from 13 countries.[2]

In 2020, Europe hosted the first Defender-Europe exercises. These had been planned as the largest US drills on the Old Continent in 25 years. Their purpose was to practise the deployment of an entire armoured division, around 20,000 troops, from the US to Europe. However, due to the outbreak of the pandemic they were limited to 6000 troops: an armoured brigade combat team and a division command post. Other, smaller exercises were also cancelled for the same reason.[3] In 2021, Defender-Europe was held in the south of the continent, but due to the ongoing pandemic only 2900 US troops took part, simulating a large-scale defence operation in the Black Sea region and in the Balkans. Defender-Europe 21 was coordinated with NATO’s major Steadfast Defender 21 exercise, whose main objective was to secure the deployment of US forces to Romania using the VJTF; some 9000 troops from 20 countries took part in this event. Steadfast Defender 21 also provided the first opportunity to test two new commands: the Joint Force Command for the Atlantic in Norfolk (USA) and the Joint Support and Enabling Command in Ulm (Germany), both of which were established following a decision taken at the 2018 NATO summit in Brussels.[4]  The following year, these exercises returned to Central and Eastern Europe: 3400 US troops practised an operation to assist Poland, Lithuania, Latvia and Slovakia, the event’s host nations, in the event they come under attack.[5]

Strengthening national exercises on the north-eastern flank

A breakthrough for military exercises on the north-eastern flank came in 2017, when four NATO battlegroups were deployed in the region. This translated into the increased participation of the allied forces in the existing exercises, and spurred the creation of a whole raft of new ones.

The Baltic states have relatively small armed forces, which severely limits the scale of regular exercises that are conducted there. In order to exceed the size of a brigade (3000–4000 soldiers), it is necessary for them to call up reservists and ensure a significant presence of allied troops. The potential of the Baltic states’ navies and air forces is limited, so the largest military exercises in Estonia (SIIL), Latvia (Namejs) and Lithuania (Iron Wolf) focus mainly on the land domain. The latter, which is the smallest of the three, focuses on the operations of a single brigade supported by allied sub-units, including a NATO battlegroup. The size of Latvian and Estonian national exercises, reinforced by allied troops, fluctuates between 8000 and 10,000 personnel.

Although Finland has much larger armed forces than the Baltic states, it does not organise single large-scale exercises that would combine multiple brigades. Each year a different unit conducts such drills, which is the largest exercise in a given year. Each year it takes place in different parts of the country under a different name. Since 2016, the biennial Arrow exercises have been Finland’s most important military drills featuring foreign partners. These involve integrating companies and platoons from the UK, the other countries of the Joint Expeditionary Force (JEF) and the US with a Finnish brigade, which results in the participation of between 2000 and 3500 troops. In 2022, a British tank company participated in the Arrow exercise for the first time.

Sweden did not conduct any exercises with a national defence scenario from 1993 to 2016. It resumed these only in 2017, when more than 19,000 troops from 10 countries, including the US, took part in the Aurora 17 exercise.[6] During this drill, Sweden tested its ability to host troops from NATO countries for the first time, securing their movement from the west to the east & south of the country, and integrating their military support. Due to the outbreak of the COVID-19 pandemic, the next Aurora exercise did not take place in 2020 as originally scheduled according to its three-year cycle, but only in 2023.  

Norway has held its Cold Response exercises in the north of its territory every two years since 2006. Norway’s most important NATO allies and regional partners have taken part in these exercises, which are the country’s largest. Initially, their scenarios envisaged crisis management in Arctic conditions, but since 2016 they have focused on high-intensity operations, that is those against a near peer adversary. Around 16,000 troops have taken part in each Cold Response exercises since 2012, with a break in 2020 due to the pandemic. In 2022, a record 35,000 troops from 27 countries were due to participate, but this number was reduced by the 5000 soldiers who were assigned other tasks following Russia’s full-scale invasion of Ukraine.[7]

Poland has held its largest exercises, Anakonda, every two years since 2006. Over this period, these have evolved from national exercise of the Polish Armed Forces into an event that involves other NATO members and has a regional dimension. In 2014, only 750 out of the 12,500 soldiers who took part came from NATO countries. A record was set in 2016, when the event brought together up to 31,000 soldiers, including 18,000 from 22 allied and partner countries. In 2018, Anakonda extended beyond Poland’s borders for the first time as the Baltic states co-hosted the event, which attracted a total of 17,500 soldiers. Due to the pandemic, the 2020 exercise was conducted in a more limited format.

Exercise Trifecta: combined Swedish, Polish and US exercises

2023 saw a far-reaching synchronisation of the military exercises of individual countries on the north-eastern flank, which came to be known as Exercise Trifecta. In the previous years, several smaller exercises held by different countries were sometimes coordinated with the larger ones in terms of their scenarios and timing, but this was the first time that the three largest national exercises were actually combined. Another new development was that this chain included the overlapping exercise in Sweden, which had begun the process of joining NATO but was still not a member. In this way, Sweden’s Aurora 23, Poland’s Anakonda 23, the US’s Defender 23 and a whole raft of smaller exercises of the countries on the north-eastern flank were combined into one very large-scale training event.

Aurora 23 was Sweden’s largest military exercise since the end of the Cold War. It took place in late April/early May 2023 with the participation of 26,000 soldiers from Sweden and 14 other countries, including the US, Poland, Norway and Finland. Its scenario assumed that Sweden had become the target of a hybrid war that escalated into an open invasion of its territory, with a particular focus on Gotland. As part of this exercise, the country’s armed forces conducted crisis management operations that evolved into a full-scale defence campaign. The training’s key component was the arrival of NATO forces, which were gradually deployed across Swedish territory as the simulated crisis unfolded.[8] Aurora 23 played out in all the domains (land, sea, air and cyber) in the southeastern part of Sweden. Poland’s task was to support the defence of Gotland: a company of the 6th Airborne Brigade (c. 120 soldiers) was assigned to parachute on the island in cooperation with the British troops, and a fire unit of the Naval Missile Unit was also deployed to the island. At the same time, Poland’s participation in Aurora marked the launch of the Polish drills.[9]

Anakonda 23 was Poland’s largest military exercise since the pandemic and Russia’s full-scale invasion of Ukraine. In May 2023, more than 12,000 soldiers of the Polish Armed Forces and several hundred troops from NATO and partner countries, including the United States, Romania, Slovenia, Sweden, France, Lithuania, Latvia, Estonia and Turkey, took part in this exercise on the territory of Poland, the Baltic states and Sweden. Its scenario assumed that an attack on Sweden would lead to an escalation of the conflict in the Baltic Sea region and to a direct attack on the territory of Poland, which would then trigger Article 5 of the Washington Treaty. All branches of armed forces were involved in this exercise; its main burden fell on the 16th and 18th Mechanised Divisions, which are both deployed in the north-eastern part of the country.[10] At the same time, US military exercises were already underway in Europe.

The DEFENDER 23 (Dynamic Employment of Forces to Europe for NATO Deterrence and Enhanced Readiness 2023) exercise consisted of three smaller drills: Swift Response 23, Immediate Response 23 and Saber Guardian 23. It ran from April to June 2023 on the training grounds of 10 European countries, and involved 7000 US troops as well as 17,000 soldiers from other countries.[11] This time it was conducted mainly in the south of Europe, as its focus alternates between Central and Southern Europe. Under a scenario that assumed an escalating armed conflict in the Nordic-Baltic region and rising tensions in the Western Balkans, the United States deployed its units along the entire NATO flank.

Swift Response 23, the first of the three exercises comprising DEFENDER 23, was held in May 2023 with the participation of 7000 airborne troops from 14 countries: the Czech Republic, Estonia, France, Germany, Greece, Hungary, Italy, Latvia, the Netherlands, Poland, Portugal, Spain, the United Kingdom and the United States. The Spanish airborne brigade played the most important role in this exercise, carrying out parachute landings in Estonia, Greece and Spain with the support of sub-units from other countries.[12] The Polish 6th Airborne Battalion (c. 600 soldiers) constituted the main core of the forces that practised in Estonia; it was supported by companies from the UK and the Czech Republic, which were dropped in the western part of the country as part of the simulated support of its defence.[13]An important part of the exercise was to synchronise the sub-units of ground troops with US transport aviation as part of the Astral Knight drill and with US naval forces during the Formidable Shield event; the aim of both of these was to increase interoperability and combat capabilities in a multi-domain environment.

The second component of DEFENDER 23 was Immediate Response 23. Under its scenario, the US made an emergency deployment of an additional battalion-size infantry task force to the Balkans in late May and early June; it joined other US forces in the region (Albania, Bulgaria, Croatia, Kosovo, Montenegro, North Macedonia and Slovenia) to practise crisis response. A total of about 2800 soldiers from the United States and 7000 troops from 10 other countries (Albania, Bulgaria, Croatia, Greece, Kosovo, Montenegro, North Macedonia, Slovenia and Turkey) participated in this event.[14]

The last large-scale exercise within DEFENDER 23, Sabre Guardian 23, took place in May and June 2023, with the involvement of more than 2400 US soldiers and 7300 troops from other countries: Bulgaria, France, Italy, the Netherlands, North Macedonia, Poland, Portugal and Romania. For the duration of this exercise, the Romanian-based headquarters of the Multinational Division South-East (MND SE) was subordinated to the US V Corps, while the US 41st Field Artillery Brigade, which had deployed to the Black Sea region and joined the US forces there, was subordinated to the HQ of the MND SE. The exercise practised a tactical road march, river crossings, responses to a simulated threat involving weapons of mass destruction (chemical, biological, radiological, nuclear) and artillery fire.[15]

In the air and at sea: Air Defender and BALTOPS

The land domain is the most important one for the countries on NATO’s eastern flank, but military exercises are not limited to the land forces only; they are supplemented by the US-led BALTOPS naval exercises in the Baltic Sea, which have been regularly held for many years, and the NATO Air Defender exercise, which Germany organised for the first time in 2023. The large-scale international live exercises (LIVEX), while the most spectacular, are not the only form of military drills: they are always accompanied by command post exercises (CPX) and study exercises.[16] In addition, alongside major events such as Aurora, Anakonda and Defender, there are a number of associated smaller ones. The most important of these are temporary reinforcements of NATO battalion-sized battlegroups to brigades, which most recently took place in May and June 2023 in Poland (the US-led Griffin Shock exercise),[17] Lithuania (the German-led Griffin Storm)[18] and Estonia (Spring Storm, involving the UK).[19]

Air Defender 23, which was held in June 2023 in Germany, was the largest air force exercise in NATO’s post-Cold War history, involving some 10,000 troops from 25 countries and 250 military aircraft of various types. During this event, a number of international task forces made up of various aircraft were formed to simulate the gaining of air superiority over the North and Baltic Seas and supporting the operations of allied troops in the Baltic states and Romania under a collective defence scenario. The drill also practised the suppression of the enemy’s air defences (SEAD) and parachute landings, while joint terminal attack controllers (JTACs) carried out their tasks. More broadly, Air Defender was the aerial supplement to Defender, Anakonda and Aurora in 2023. It is set to become a cyclical training event which will be permanently hosted by Germany.[20]

The BALTOPS exercises, which the United States has been organising since 1971, were and still are the largest naval military drills in the Baltic Sea. In June 2023, 50 ships, more than 45 aircraft and around 6000 troops from 20 countries took part in this exercise. NATO allies and their partners practised protecting convoys, fighting submarines and surface ships, and carrying out landing operations near Ustka, Klaipeda (Lithuania) and Ventspils (Latvia). Moreover, they tested new methods of cooperation with civilian ships and shipowners.[21]


Despite the scale and intensity of the military exercises that took place on NATO’s eastern flank in 2023, they are still dwarfed by the size of similar Cold War-era events such as REFORGER (REturn of FORces to GERmany). Given the drastic downsizing of the NATO countries’ armed forces, it is currently impossible to re-enact scenarios simultaneously involving several armies or even corps. However, a much higher level of interoperability has been achieved by integrating multinational sub-units even at the company level, and not only in the format of battlegroups.

The Air Defender 23 and BALTOPS 23 exercises and those involving the reinforcements of NATO battalion-sized battlegroups up to brigade level were not formally part of the Exercise Trifecta, but they were integrated into the series of main training events in the broader sense by virtue of their convergence in terms of time, geography and scenarios. Taken together, international military exercises on the north-eastern flank had never reached such proportions before, and above all, had never been so strongly interconnected: the full spectrum of defensive actions in response to a potential Russian attack was tested almost simultaneously.

While growing numbers of troops and allies are participating in major US and NATO exercises, the strictly national drills are beginning to play a supporting role by preparing and certifying units for their integration into the multinational structures. Most of NATO’s smaller members and those situated far away from the north-eastern flank are joining these structures by pinning their sub-units and capabilities to larger allied formations. Civil-military coordination remains a key element of these exercises as it develops cooperation between local authorities and the military, and integrates aspects of civil defence and military mobility into the exercises. Reserve soldiers are rarely called up for multinational exercises, but their participation will increase following the accession to NATO of Finland, whose armed forces are based on universal compulsory service, and the expansion of partial conscription in those member states that use it, such as Denmark, Sweden, Norway, Lithuania, Latvia and Estonia.

The experiences of 2023 will serve as the starting point for future NATO military exercises that will practise the implementation of the regional defence plans adopted at the Vilnius Summit.[22] In the coming years, the levels of complexity, coordination and internationalisation of exercises on NATO’s north-eastern flank will increase further. They will likely begin with national scenarios and then move seamlessly to allied operations. The Allied forces assigned to implement defence plans will cooperate under newly created and existing NATO command structures in the region and at the strategic level. Without doubt, however, the further adaptation of Allied exercises will entail higher costs and require increased defence spending.


[1]   ‘Trident Juncture 2018’, NATO, 29 October 2018, nato.int.

[2]Press Release – Exercise Saber Strike 22 begins’, U.S. Army Europe and Africa, 24 February 2022, europeafrica.army.mil.

[3]   ‘Aktualizacja informacji nt. Defender-Europe 20’, Ambasada i Konsulat USA w Polsce, 16 March 2020, pl.usembassy.gov.

[4]   They were used to redeploy troops by sea from the US to Europe (JFC Norfolk) and to redeploy troops in Europe (JSEC in Ulm).

[5]   W. Lorenz, ‘Defender Europe 21: Importance of the Military Exercises for Defence and Deterrence in Europe’, The Polish Institute of International Affairs, 5 July 2021, pism.pl.; ‘DEFENDER-Europe 22 Fact Sheet’, U.S. Army Europe and Africa, 3 May 2022, europeafrica.army.mil.

[6]   J. Gotkowska, ‘Aurora: Sweden’s response to Zapad?’, OSW, 20 September 2017, osw.waw.pl.

[7]   Ø.F. Olsen, ‘Cold Response: 5.000 færre deltakende soldater enn planlagt’, Forsvarets Forum, 7 March 2022, forsvaretsforum.no.

[8]   ‘Defence exercise Aurora 23’, The Swedish Armed Forces, 16 May 2023, forsvarsmakten.se.

[9]Największe od 25 lat ćwiczenie wojskowe w Szwecji pk. Aurora 23 z udziałem polskich spadochroniarzy’, 6 Brygada Powietrznodesantowa, 9 May 2023, wojsko-polskie.pl.

[11]About DEFENDER 23’, U.S. Army Europe and Africa, europeafrica.army.mil.

[12]News Release Swift Response 23, first of three, major DEFENDER 23-linked exercises, to begin’, U.S. Army Europe and Africa, 2 May 2023, europeafrica.army.mil.

[13]Swift Response 23’, 6. Brygada Powietrznodesantowa, 17 May 2023, wojsko-polskie.pl.

[14]News Release – Immediate Response 23, second of three major DEFENDER 23-linked exercises, to begin’, U.S. Army Europe and Africa, 17 May 2023, europeafrica.army.mil.

[15] T. Welch, ‘Final DEFENDER 23 exercise, Saber Guardian 23, begins’, U.S. Army, 24 May 2023, army.mil.

[16] Real military forces take part in live exercises. Command post exercises are conducted by commands with the participation of commanders and their staffs, involving internal and inter-command communications; forces and means are only simulated. Study exercises may involve maps, wargames, a series of lectures, a discussion group or operational analysis.

[17]News Release: U.S. and NATO troops execute combined exercise to expand Battle Group in Poland’, U.S. Army Europe and Africa, 11 May 2023, europeafrica.army.mil.

[18] J. Gotkowska, J. Graca, ‘A German brigade permanently stationed in Lithuania?’, OSW, 30 June 2023, osw.waw.pl.

[20]Air Defender 23’, Bundeswehr, 22 June 2023, bundeswehr.de.

[21]BALTOPS 23 concludes in Kiel, Germany’, U.S. Naval Forces Europe and Africa / U.S. Sixth Fleet, 16 June 2023, c6f.navy.mil.

[22] J. Gotkowska, J. Graca et al., ‘NATO Summit in Vilnius: breakthroughs and unfulfilled hopes’, OSW Commentary, no. 526, 13 July 2023, osw.waw.pl.