Amid the growing concerns about Russia’s aggression, Finland has officially become a member of the North Atlantic Treaty Organization, more commonly known as NATO on Tuesday.

Finland applied to join NATO in May 2022, after Russia invaded Ukraine. Russian President Vladimir Putin has long complained about NATO’s expansion toward his nation and the latest move is another blow toward the same.

Kremlin spokesman Dmitry Peskov called Helsinki’s move to join the bloc an “encroachment” on Russia’s security and said the structure of NATO was hostile towards Russia.

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The organization celebrated the latest addition to its flock with a ceremony outside of its Brussels headquarters where Finland’s blue and white flag flew high among those of its partners. Which brings to question — how many partners does it actually have?

How many countries are in NATO?

With the addition of Finland, the total number of countries joining NATO becomes 31.

According to its website, “in 1949, there were 12 founding members of the Alliance: Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom and the United States. Since then, 19 more countries have joined the Alliance: Greece and Türkiye (1952); Germany (1955); Spain (1982); Czechia, Hungary and Poland (1999); Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia (2004); Albania and Croatia (2009); Montenegro (2017); North Macedonia (2020); and Finland (2023).”

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Incidentally, Finland happens to join NATO on a very important date — it is the organization’s birthday. Tuesday marks the 74th anniversary of the signing of its founding Washington Treaty on April 4, 1949. The date also coincides with a meeting of the alliance’s foreign ministers.

Article 10 of the North Atlantic Treaty states that membership is open to any “European State in a position to further the principles of this Treaty and to contribute to the security of the North Atlantic area”. For a country to join NATO, all of its allies have to be on board.