NATO was established on April 4, 1949, with 12 founding member states. The original signatories were countries from North America and Western Europe who came together to form a collective defense organization. NATO's formation was a response to the growing influence of the Soviet Union and the threat of communist expansion during the early stages of the Cold War.
Expansion of NATO: Since its founding, NATO's membership has expanded to include numerous other countries, especially after the end of the Cold War, with a focus on integrating former Warsaw Pact members and former Soviet republics.