NATO: An Overview of the Alliance's Mission and Structure (nato.int)

• Founded in 1949 with 12 members, now 32.
• Collective defense (Article 5) is the cornerstone.
• 2022 Strategic Concept defines three core tasks.

"NATO is a political and military alliance of 32 countries in Europe and North America, founded in 1949 to safeguard members' freedom and security. Its core principle is collective defense: an attack on one is an attack on all. The Alliance's 2022 Strategic Concept outlines three core tasks: deterrence and defense, crisis prevention and management, and cooperative security. Decisions are made by consensus. Membership is open to European states meeting conditions, requiring unanimous consent of existing Allies."