The North Atlantic Treaty Organization, or NATO, is a military alliance established in 1949 to ensure collective defense among its member countries. It was formed in response to the threat posed by the Soviet Union during the Cold War, promoting stability and security in the North Atlantic region. NATO's primary purpose is to provide mutual defense against aggression, meaning that an attack on one member is considered an attack on all. Today, it includes 30 member countries and continues to adapt to new security challenges, such as terrorism and cyber threats, while fostering cooperation among its allies.