BRUSSELS — Finland joined the NATO military alliance Tuesday, dealing a major blow to Russia with a historic realignment of the continent triggered by Moscow’s invasion of Ukraine.
The Nordic country’s membership doubles Russia’s border with the world’s biggest security alliance and represents a major change in Europe’s security landscape: The nation adopted neutrality after its defeat by the Soviets in World War II. But its leaders signaled they wanted to join the alliance just months after Russian President Vladimir Putin’s invasion of Ukraine sent a shiver of fear through Moscow’s neighbors.
The move is a strategic and political blow to Putin, who has long complained about NATO’s expansion toward Russia and partly used that as a justification for the invasion.

Johanna Geron, Pool Photo via AP
Finnish Foreign Minister Pekka Haavisto, left, hands over his nation's accession document to United States Secretary of State Antony Blinken, right, during a meeting of NATO foreign ministers at NATO headquarters in Brussels, Tuesday, April 4, 2023.
Russia warned that it would be forced to take “retaliatory measures” to address what it called security threats created by Finland’s membership. It had also warned it would bolster forces near Finland if NATO sends any additional troops or equipment to what is its 31st member country.
The alliance says it poses no threat to Moscow.
Neighboring Sweden, which has avoided military alliances for more than 200 years, has also applied. But objections from NATO members Turkey and Hungary have delayed the process.
Alarmed by Moscow’s invasion of Ukraine last year, Finland, which shares a 1,340 kilometer (832 mile) border with Russia, applied to join in May, setting aside years of military non-alignment to seek protection under the organization’s security umbrella. Read more here:
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Finland’s NATO membership: What’s next?
AP Photo/Burhan Ozbilici
Turkey and Hungary dispatch acceptance letters to the United States which is the depositary, or safekeeper, of NATO under the alliance's 1949 founding treaty. The letters will be filed in the archives of the U.S. State Department, which will notify NATO Secretary-General Jens Stoltenberg that the conditions for inviting Finland to become a member were met.
AP Photo/Burhan Ozbilici
Turkey and Hungary dispatch acceptance letters to the United States which is the depositary, or safekeeper, of NATO under the alliance's 1949 founding treaty. The letters will be filed in the archives of the U.S. State Department, which will notify NATO Secretary-General Jens Stoltenberg that the conditions for inviting Finland to become a member were met.
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Finland’s NATO membership: What’s next?
AP Photo/Virginia Mayo
NATO sends a letter signed by Stoltenberg inviting Finland to join the military alliance.
AP Photo/Virginia Mayo
NATO sends a letter signed by Stoltenberg inviting Finland to join the military alliance.
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Finland’s NATO membership: What’s next?
Markku Ulander/Lehtikuva via AP
Finland sends its own acceptance document, signed by Foreign Minister Pekka Haavisto, to the U.S. State Department. Finnish President Sauli Niinistö, pictured, authorized Haavisto to sign the document. Either the Finnish Embassy in Washington or a Finnish government official will deliver the document.
Markku Ulander/Lehtikuva via AP
Finland sends its own acceptance document, signed by Foreign Minister Pekka Haavisto, to the U.S. State Department. Finnish President Sauli Niinistö, pictured, authorized Haavisto to sign the document. Either the Finnish Embassy in Washington or a Finnish government official will deliver the document.
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Finland’s NATO membership: What’s next?
AP Photo/Denes Erdos
Once Finland's membership acceptance document reaches the State Department in Washington, the country officially becomes a NATO member.
AP Photo/Denes Erdos
Once Finland's membership acceptance document reaches the State Department in Washington, the country officially becomes a NATO member.
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Finland’s NATO membership: What’s next?
AP Photo/Burhan Ozbilici
Finland and neighboring Sweden jointly applied for NATO membership in May 2022. The countries, which have close cultural, economic and political ties, planned to enter the alliance simultaneously.
Sweden's bid, however, has stalled due to opposition from Turkey, whose president has said his country wouldn't ratify membership before disputes between Ankara and Stockholm were resolved. The Turkish government has accused Sweden of being too soft on groups that it deems to be terror organizations.
Hungary's parliament also has yet to ratify Sweden's accession to NATO, and it remains unclear when it will do so.
AP Photo/Burhan Ozbilici
Finland and neighboring Sweden jointly applied for NATO membership in May 2022. The countries, which have close cultural, economic and political ties, planned to enter the alliance simultaneously.
Sweden's bid, however, has stalled due to opposition from Turkey, whose president has said his country wouldn't ratify membership before disputes between Ankara and Stockholm were resolved. The Turkish government has accused Sweden of being too soft on groups that it deems to be terror organizations.
Hungary's parliament also has yet to ratify Sweden's accession to NATO, and it remains unclear when it will do so.

Sergei Grits, Associated Press
NATO flag, centre, and Finland flags flutter over the building of Ministry of Foreign Affairs in Helsinki, Finland, Tuesday, April 4, 2023.