On this day in 1949, the U.S., U.K., Canada and nine European countries establish NATO. Article 5 of the alliance’s charter affirms that an attack on one member nation will be considered an attack on all members. Not until 9/11 will this provision be invoked.

On this day in 1949, the U.S., U.K., Canada and nine European countries establish NATO. Article 5 of the alliance’s charter affirms that an attack on one member nation will be considered an attack on all members. Not until 9/11 will this provision be invoked. pic.twitter.com/P3dfDVbXz7

— Military History Now (@MilHistNow) April 4, 2025