NATO Enlargement to Sweden and Finland
link to page 3 
INSIGHTi
NATO Enlargement to Sweden and Finland
Updated March 22, 2024
Sweden joined NATO on March 7, 2024, enlarging the alliance to 32 members (see Figure 1). Amid
heightened security concerns about Russia after its February 2022 invasion of Ukraine, both Finland and
Sweden applied to join NATO in May 2022 with the intention to accede to the alliance together. Finland
joined on April 4, 2023, but Sweden’s accession was delayed by issues raised by Turkey (Türkiye) and
Hungary. The Biden Administration and majorities in the House and Senate expressed support for NATO
enlargement to both Finland and Sweden, viewing the addition of these two mature democracies with
capable militaries as enhancing Euro-Atlantic security and advancing U.S. interests.
Finland and Sweden Apply for NATO Membership
Finland’s and Sweden’s applications to NATO marked a historic shift for these traditionally militarily
nonaligned countries that for decades sought to balance political, economic, and cultural ties to the West
and relations with Russia. After the Cold War, Finland and Sweden joined the European Union (EU) and
established close partnerships with NATO. Both Finland and Sweden have participated in numerous
NATO operations over the years, and the two countries have advanced militaries that are interoperable
with NATO. Public support for NATO membership—and the added security of NATO’s “Article 5”
mutual defense clause—skyrocketed in both countries following Russia’s invasion of Ukraine; polls
indicate support at 82% in Finland (as of November 2023) and 60% in Sweden (as of March 2024).
U.S. officials from the Departments of State and Defense concurred with Finnish and Swedish assertions
that the two countries would strengthen NATO’s defense posture, especially in the Baltic Sea region.
Finland spends nearly 2.5% of its GDP on defense (above NATO’s 2% spending guideline). Sweden
intends to meet NATO’s 2% defense spending goal in 2024.
Some analysts expressed concern about NATO’s ability to defend Finland’s 830-mile border with Russia
(which doubles NATO’s overall borders with Russia). Finnish officials contend that Finland has long
defended its own borders and will continue to do so as a NATO member. Finland and Sweden also have
strong traditions of societal resilience and experience dealing with Russian disinformation efforts,
cyberattacks, and hybrid threats. Russia has largely sought to downplay concerns about Finnish and
Swedish accession to NATO, but Russian President Vladimir Putin has warned NATO against deploying
troops or expanding military infrastructure in either country. In the period before Finland’s and Sweden’s
accession, the United States and NATO enhanced defense cooperation and conducted more joint training
exercises with Finland and Sweden, in part to provide security reassurances to both countries.
Congressional Research Service
https://crsreports.congress.gov
IN11949
CRS INSIGHT
Prepared for Members and
Committees of Congress
Congressional Research Service
2
The Path to NATO Accession
For a new member to be admitted to NATO, all allies must approve. Allied governments unanimously
agreed to invite Finland and Sweden to join NATO at the alliance’s June 2022 Madrid Summit, following
a trilateral agreement concluded to address terrorism and other security concerns raised by Turkey and
gain Turkey’s support for the formal start of NATO’s accession process. In July 2022, allied governments
signed protocols to NATO’s founding North Atlantic Treaty that had to be ratified by each ally (according
to national procedures) to allow Finland and Sweden to join the alliance.
Twenty-eight of NATO’s then-30 allies concluded the ratification process for both Finland and Sweden by
late September 2022. Turkey, however, remained concerned about what it viewed as Swedish—and to a
lesser extent Finnish—support for pro-Kurdish and other groups that Turkey regards as terrorist entities.
In March 2023, Turkish President Recep Tayyip Erdogan announced his satisfaction with Finnish efforts
to address Turkey’s concerns; Turkey’s parliament subsequently ratified Finland’s accession but not
Sweden’s. Turkey continued to press Sweden to grant Turkish extradition requests and take a harder line
against pro-Kurdish groups. Hungary’s issues with Finland and Sweden were more opaque but largely
centered on grievances over past EU and Swedish criticisms of Hungarian government policies perceived
as eroding the rule of law. Hungary’s parliament approved Finland’s accession in March 2023 but delayed
voting on Sweden’s.
Swedish and NATO officials maintained that Sweden’s accession was not a question of “whether” but
“when.” Sweden continued working to address Turkey’s concerns, including by passing new anti-
terrorism legislation. In July 2023, Turkish President Erdogan agreed to move forward with ratifying
Sweden’s accession. President Erdogan also publicly linked parliamentary approval of Sweden’s
accession to a possible U.S. sale of F-16 fighter jets to Turkey (although U.S. officials asserted that the
two issues were separate). Turkey ultimately ratified Sweden’s accession in late January 2024, and
Hungary did so in late February 2024. Following Turkey’s ratification, the Biden Administration formally
notified Congress of the intended F-16 sale to Turkey. A new defense industrial agreement between
Sweden and Hungary (including a deal to sell four Swedish-built Gripen fighter jets to Hungary) may
have helped facilitate Hungary’s approval of Sweden’s accession.
Congressional Role and Interests in the Accession Process
In the United States, once NATO members sign accession protocols, the Administration sends them to the
Senate for its advice and consent as part of the ratification process (see CRS Report 98-384, Senate
Consideration of Treaties). President Biden submitted accession protocols for Finland and Sweden to the
Senate on July 11, 2022. The Senate Foreign Relations Committee subsequently reported favorably on the
resolution of ratification, and the full Senate approved it on August 3, 2022, by a vote of 95-1. President
Biden signed the accession protocols for both Finland and Sweden on August 9, 2022, completing the
U.S. ratification process. The House also passed a resolution of support for Finland and Sweden’s NATO
accession (H.Res. 1130) in July 2022 by a vote of 394-18.
Some Members of Congress expressed concerns about Turkey’s and Hungary’s delays in approving
Finland and Sweden as NATO members. In February 2023, for example, a group of 29 Senators asserted
that Turkey’s delay “threatens the Alliance’s unity” and noted they would not consider supporting the U.S.
sale of F-16s to Turkey until Turkey ratified Finnish and Swedish accession. In February 2024, some
Members also urged Hungary to swiftly ratify Sweden’s accession.
Congressional Research Service
3
Figure 1. NATO Members and Aspirants
Source: CRS Graphics. Map updated March 2024.
Congressional Research Service
4
Author Information
Kristin Archick
Andrew S. Bowen
Specialist in European Affairs
Analyst in Russian and European Affairs
Paul Belkin
Analyst in European Affairs
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff
to congressional committees and Members of Congress. It operates solely at the behest of and under the direction of
Congress. Information in a CRS Report should not be relied upon for purposes other than public understanding of
information that has been provided by CRS to Members of Congress in connection with CRS’s institutional role.
CRS Reports, as a work of the United States Government, are not subject to copyright protection in the United
States. Any CRS Report may be reproduced and distributed in its entirety without permission from CRS. However,
as a CRS Report may include copyrighted images or material from a third party, you may need to obtain the
permission of the copyright holder if you wish to copy or otherwise use copyrighted material.
IN11949 · VERSION 7 · UPDATED
INSIGHTi
NATO Enlargement to Sweden and Finland
Updated March 22, 2024
Sweden joined NATO on March 7, 2024, enlarging the alliance to 32 members (see Figure 1). Amid
heightened security concerns about Russia after its February 2022 invasion of Ukraine, both Finland and
Sweden applied to join NATO in May 2022 with the intention to accede to the alliance together. Finland
joined on April 4, 2023, but Sweden’s accession was delayed by issues raised by Turkey (Türkiye) and
Hungary. The Biden Administration and majorities in the House and Senate expressed support for NATO
enlargement to both Finland and Sweden, viewing the addition of these two mature democracies with
capable militaries as enhancing Euro-Atlantic security and advancing U.S. interests.
Finland and Sweden Apply for NATO Membership
Finland’s and Sweden’s applications to NATO marked a historic shift for these traditionally militarily
nonaligned countries that for decades sought to balance political, economic, and cultural ties to the West
and relations with Russia. After the Cold War, Finland and Sweden joined the European Union (EU) and
established close partnerships with NATO. Both Finland and Sweden have participated in numerous
NATO operations over the years, and the two countries have advanced militaries that are interoperable
with NATO. Public support for NATO membership—and the added security of NATO’s “Article 5”
mutual defense clause—skyrocketed in both countries following Russia’s invasion of Ukraine; polls
indicate support at 82% in Finland (as of November 2023) and 60% in Sweden (as of March 2024).
U.S. officials from the Departments of State and Defense concurred with Finnish and Swedish assertions
that the two countries would strengthen NATO’s defense posture, especially in the Baltic Sea region.
Finland spends nearly 2.5% of its GDP on defense (above NATO’s 2% spending guideline). Sweden
intends to meet NATO’s 2% defense spending goal in 2024.
Some analysts expressed concern about NATO’s ability to defend Finland’s 830-mile border with Russia
(which doubles NATO’s overall borders with Russia). Finnish officials contend that Finland has long
defended its own borders and will continue to do so as a NATO member. Finland and Sweden also have
strong traditions of societal resilience and experience dealing with Russian disinformation efforts,
cyberattacks, and hybrid threats. Russia has largely sought to downplay concerns about Finnish and
Swedish accession to NATO, but Russian President Vladimir Putin has warned NATO against deploying
troops or expanding military infrastructure in either country. In the period before Finland’s and Sweden’s
accession, the United States and NATO enhanced defense cooperation and conducted more joint training
exercises with Finland and Sweden, in part to provide security reassurances to both countries.
Congressional Research Service
https://crsreports.congress.gov
IN11949
CRS INSIGHT
Prepared for Members and
Committees of Congress
Congressional Research Service
2
The Path to NATO Accession
For a new member to be admitted to NATO, all allies must approve. Allied governments unanimously
agreed to invite Finland and Sweden to join NATO at the alliance’s June 2022 Madrid Summit, following
a trilateral agreement concluded to address terrorism and other security concerns raised by Turkey and
gain Turkey’s support for the formal start of NATO’s accession process. In July 2022, allied governments
signed protocols to NATO’s founding North Atlantic Treaty that had to be ratified by each ally (according
to national procedures) to allow Finland and Sweden to join the alliance.
Twenty-eight of NATO’s then-30 allies concluded the ratification process for both Finland and Sweden by
late September 2022. Turkey, however, remained concerned about what it viewed as Swedish—and to a
lesser extent Finnish—support for pro-Kurdish and other groups that Turkey regards as terrorist entities.
In March 2023, Turkish President Recep Tayyip Erdogan announced his satisfaction with Finnish efforts
to address Turkey’s concerns; Turkey’s parliament subsequently ratified Finland’s accession but not
Sweden’s. Turkey continued to press Sweden to grant Turkish extradition requests and take a harder line
against pro-Kurdish groups. Hungary’s issues with Finland and Sweden were more opaque but largely
centered on grievances over past EU and Swedish criticisms of Hungarian government policies perceived
as eroding the rule of law. Hungary’s parliament approved Finland’s accession in March 2023 but delayed
voting on Sweden’s.
Swedish and NATO officials maintained that Sweden’s accession was not a question of “whether” but
“when.” Sweden continued working to address Turkey’s concerns, including by passing new anti-
terrorism legislation. In July 2023, Turkish President Erdogan agreed to move forward with ratifying
Sweden’s accession. President Erdogan also publicly linked parliamentary approval of Sweden’s
accession to a possible U.S. sale of F-16 fighter jets to Turkey (although U.S. officials asserted that the
two issues were separate). Turkey ultimately ratified Sweden’s accession in late January 2024, and
Hungary did so in late February 2024. Following Turkey’s ratification, the Biden Administration formally
notified Congress of the intended F-16 sale to Turkey. A new defense industrial agreement between
Sweden and Hungary (including a deal to sell four Swedish-built Gripen fighter jets to Hungary) may
have helped facilitate Hungary’s approval of Sweden’s accession.
Congressional Role and Interests in the Accession Process
In the United States, once NATO members sign accession protocols, the Administration sends them to the
Senate for its advice and consent as part of the ratification process (see CRS Report 98-384, Senate
Consideration of Treaties). President Biden submitted accession protocols for Finland and Sweden to the
Senate on July 11, 2022. The Senate Foreign Relations Committee subsequently reported favorably on the
resolution of ratification, and the full Senate approved it on August 3, 2022, by a vote of 95-1. President
Biden signed the accession protocols for both Finland and Sweden on August 9, 2022, completing the
U.S. ratification process. The House also passed a resolution of support for Finland and Sweden’s NATO
accession (H.Res. 1130) in July 2022 by a vote of 394-18.
Some Members of Congress expressed concerns about Turkey’s and Hungary’s delays in approving
Finland and Sweden as NATO members. In February 2023, for example, a group of 29 Senators asserted
that Turkey’s delay “threatens the Alliance’s unity” and noted they would not consider supporting the U.S.
sale of F-16s to Turkey until Turkey ratified Finnish and Swedish accession. In February 2024, some
Members also urged Hungary to swiftly ratify Sweden’s accession.
Congressional Research Service
3
Figure 1. NATO Members and Aspirants
Source: CRS Graphics. Map updated March 2024.
Congressional Research Service
4
Author Information
Kristin Archick
Andrew S. Bowen
Specialist in European Affairs
Analyst in Russian and European Affairs
Paul Belkin
Analyst in European Affairs
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff
to congressional committees and Members of Congress. It operates solely at the behest of and under the direction of
Congress. Information in a CRS Report should not be relied upon for purposes other than public understanding of
information that has been provided by CRS to Members of Congress in connection with CRS’s institutional role.
CRS Reports, as a work of the United States Government, are not subject to copyright protection in the United
States. Any CRS Report may be reproduced and distributed in its entirety without permission from CRS. However,
as a CRS Report may include copyrighted images or material from a third party, you may need to obtain the
permission of the copyright holder if you wish to copy or otherwise use copyrighted material.
IN11949 · VERSION 7 · UPDATED