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“Discover the 32 NATO member countries and their joining timeline, plus explore the alliance’s key treaty articles—especially the vital Article 5 on collective defense—demystified in our in-depth NATO breakdown.”

Who’s in NATO & What Are Its Key Articles?

NATO Membership at a Glance
The North Atlantic Treaty Organization (NATO) is a prominent political and military alliance founded in 1949. Originally consisting of 12 founding countries, the alliance has expanded over the decades and now includes 32 member nations spanning Europe and North America .

Member Countries (Alphabetical order):
Albania, Belgium, Bulgaria, Canada, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Lithuania, Luxembourg, Montenegro, Netherlands, North Macedonia, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Turkey, United Kingdom, United States.

Notably, Finland joined in April 2023 as the 31st member, followed by Sweden in March 2024, marking a historic shift from decades of neutrality for these nations.

Key Articles of the North Atlantic Treaty

• Article 5 – Collective Defense:
  The core of NATO’s strength lies in Article 5, which states:
  “An armed attack against one or more of them in Europe or North America shall be considered an attack against them all.”
  This builds mutual defense into the fabric of the alliance, obliging members to defend one another. It has been invoked only once—after the September 11, 2001 terrorist attacks.
• Article 10 – Membership Criteria:
  Article 10 outlines how new members can be admitted: any European state willing and able to uphold the principles of the Treaty and contribute to North Atlantic security may be invited, subject to unanimous approval by existing members.

Summary Table