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NATO Needs an Island Chain Strategy for the Baltic Sea

Henri Winberg

As the upcoming NATO Summit in Vilnius (11-12 July) welcomes Finland as a new member and while Sweden awaits approval to join NATO, the article looks at how NATO should re-evaluate its approach to the Baltic Sea region, especially surrounding strategic assets.

Defense Exercise Aurora 23 on Gotland
Swedish Armed Forces exercising on Gotland during Aurora 23, May 2023.

The next NATO Summit in Vilnius, Lithuania, the first in years to be held in Eastern Europe, will present NATO with an ample opportunity to reevaluate its approach to Baltic Sea security. It will also be the first summit with Finland as a member of NATO while Sweden awaits approval from two countries – Türkiye and Hungary – to conclude the ratification process. With Sweden and Finland in the alliance, NATO should re-evaluate its approach to the Baltic Sea region, especially surrounding strategic assets. The Baltic Sea region is home to many strategic islands near Russia, however, currently these strategic islands are insufficiently defended and underutilized. Given the region’s tense security situation and Russia’s invasion of Ukraine, it’s time for NATO to realize the vitality of the Baltic Sea’s strategic islands to the alliance. The most viable option for these strategic islands, which are located near vital trade routes, undersea cables and Russian military bases, is to create a Baltic Sea version of the island chain strategy in the Pacific Ocean. At the present moment, the key islands in the Baltic are scarcely populated, lacking infrastructure and having a low military presence; getting adequate defensive capabilities to the islands will require strong political will and substantial investments. However, in the long run, an island chain strategy would increase regional security and curb Russia’s possibilities to destabilize the region. 

The Most Strategic Locations in the Baltic Sea

Denmark, Sweden and Finland have considerable island possessions in the Baltic Sea: Denmark has Bornholm, Sweden holds Gotland and Finland possesses Åland. However, the extent of each country's military presence and the political situation between the islands differs substantially and is influenced by each country’s strategic doctrine, defense spending, and the history of the islands themselves.

Little attention has been paid to the Danish island of Bornholm, located between Sweden and Poland. However, last year’s Nord Stream explosions and the recent revelations of Russian vessels charting for strategic cables and pipelines near the island has given Bornholm renewed significance. The military presence on the island is modest. Since 2000, the Danish Home Guard – a voluntary part of the Danish military – has been responsible for the island’s defense. Russia’s recent activity near the island, as well as Bornholm’s proximity to Russia's Baltic Sea fleet headquarters in Kaliningrad, clearly showcase the importance of Bornholm, with Danish politicians calling for a standing force on the island. 

The Swedish island of Gotland, the largest island in the Baltic Sea, similarly has modest military capabilities. For most of the Cold War, Sweden hosted a large military presence on the island. However, these forces were scaled back after the Cold War, and by 2005 the island’s defensive capabilities were almost nonexistent. After Russia’s annexation of Crimea in 2014, Sweden re-raised the Gotland Regiment in 2018. In recent years, Sweden has relocated a mechanized battalion and anti-aircraft capabilities, as well as put aside specific financing of $163 million for the defense of the island. The current military presence is however far from what it was at the height of the Cold War.

Whereas Bornholm and Gotland are integrated parts of their respective countries, Åland has a different status. Åland, part of Finland since 1809, has been an autonomous region of Finland since 1922. Åland has been demilitarized by international treaties since 1856, although Finland is still responsible for its defense. This creates a gap in a strategically important region. Due to this excellent location, some experts have described Åland as the Achilles heel of the Finnish defense. While the status of Åland is complex and would require considerable political will to change, it doesn’t mean Finland nor NATO couldn’t use the geostrategic island in other ways, such as securing infrastructure and trade. 

Russia’s Historical Interest – and Implications for Today

While many Great Powers have shown a considerable interest in the islands historically, none have however shown as much interest as Russia and the former Soviet Union. Russia’s historic interest can be clearly seen from its actions during the Second World War, when it occupied Bornholm for 10 months from 1945-1946. Russia is still interested, as seen in its opposition to an updated defense agreement between Denmark and the US, which could see foreign troops being placed on Bornholm.

Gotland hasn’t seen military action during the last two centuries. However, during the Finnish War of 1808-1809, fought between Russia and Sweden, Russia briefly occupied the whole island due to its strategic location. Gotland, which has been called an unsinkable aircraft carrier due to its excellent location in the middle of the Baltic Sea, remains of interest for  Russia today. Sweden has been wary about Russia’s increasing number of vessels in the Baltic Sea, including landing ships; the increase may be a power play by Moscow to demonstrate its ability to take over Gotland. 

Åland was part of the Russian Empire from 1809-1917. While Åland was demilitarized in the 1850’s to hamper Russia from using a geostrategically important region, the current state of affairs benefits Russia. There is increasing support in Finland to end Åland’s demilitarization, a move the island’s own Head of Government however opposes. With Finland’s recent membership of NATO, discussions surrounding the future of Åland will certainly pick up. While ending the demilitarization of Åland could give Finland another strategically important asset for its defense, it could also risk alienating the island’s local population, who strongly see their autonomy as linked to the demilitarization. If Finland and NATO want to make Åland an asset for the alliance, they need to engage Åland’s local government in major decisions, or otherwise risk alienating the island’s population.

A German Navy sailor taking part of NATO's BALTOPS 23 exercise in the Baltic Sea, June 2023.

Creating an Island Chain Strategy in the Baltic Sea

Given the importance of the Baltic Sea islands, both for their respective countries in the region and for NATO, it’s time for NATO to create a new strategy that takes advantage of these vital assets. Given the enlargement of NATO, which brings all three major islands under the same defensive alliance, it could be time for NATO to propose a Baltic Sea version of the longstanding American defense strategy in the Pacific Ocean, the island chain strategy. The island chain strategy is a plan where the United States and its allies in the region have built multiple lines of defense capabilities in the Pacific Ocean, stretching across the region, in order to secure their maritime security.  

A similar island chain strategy should be in place in the Baltic Sea, with the region’s larger islands Bornholm, Gotland and Åland at the core. Not only would a stronger military presence on these islands bolster NATO’s defensive capabilities in the region, especially its maritime and aerial presence, but it would also help the alliance to secure its vital infrastructure in the region. Many countries in the region are dependent on maritime trade, and the Baltic Sea is filled with important undersea cables and pipelines. This new strategy could play a vital role to the region's economic stability and energy supply – including for the three Baltic countries, Poland, and Germany. Although NATO arranges large-scale military exercises in the Baltic Sea, such as Aurora and BALTOPS, it isn’t a replacement for permanent military presence on the islands. 

Russia is also aware of this new security reality and has started to increase capabilities on its own island possessions in the Baltic Sea, such as on the strategic island of Gogland. As Russia’s exports are in large part dependent on Baltic Sea trade, even after the sanctions, Moscow wants to make sure it can eventually control the Baltic Sea during a conflict. This can be clearly seen from Moscow’s focus on maritime capabilities in Europe, even during Russia’s ongoing invasion of Ukraine. 

NATO’s New Frontier

Bornholm, Gotland and Åland represent simultaneously NATO’s greatest strength and vulnerability in the Baltic Sea region. If the islands were properly utilized, they could provide NATO with the much needed strategic depth and geopolitical advantage in the Baltic, and bolster NATO’s defensive capabilities in the region. But if the islands are left without proper attention, they can also be NATO’s biggest vulnerability against Russia’s potential ambitions in the region. Given the region’s tense security situation and Russia’s invasion of Ukraine, it’s time for NATO to realize the vitality of the region’s strategic islands to the alliance. NATO needs to seriously discuss the future of the islands during the NATO summit in Vilnius and consider concrete proposals surrounding the future of the islands. A Baltic Sea version of the island chain strategy would be the most viable option. In the long run, an island chain strategy would increase regional security and deter Russia from potentially destabilizing the region.  

About the Author

Henri Winberg

Henri Winberg

Staff Assistant Intern, Global Europe Program
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Global Europe Program

The Global Europe Program is focused on Europe’s capabilities, and how it engages on critical global issues.  We investigate European approaches to critical global issues. We examine Europe’s relations with Russia and Eurasia, China and the Indo-Pacific, the Middle East and Africa. Our initiatives include “Ukraine in Europe” – an examination of what it will take to make Ukraine’s European future a reality.  But we also examine the role of NATO, the European Union and the OSCE, Europe’s energy security, transatlantic trade disputes, and challenges to democracy. The Global Europe Program’s staff, scholars-in-residence, and Global Fellows participate in seminars, policy study groups, and international conferences to provide analytical recommendations to policy makers and the media.  Read more