What did Article 5 of the North Atlantic Treaty state?

Article 5 of the North Atlantic Treaty, signed in 1949, states that an armed attack against one or more NATO member countries is considered an attack against all member nations. This principle of collective defense obligates members to respond to such an attack, including the use of armed force if necessary. It emphasizes solidarity among NATO allies, reinforcing the commitment to mutual defense in the face of aggression. This article has been a cornerstone of NATO's security framework since its inception.