The military alliance formed in 1949 in response to Soviet aggression is called the North Atlantic Treaty Organization (NATO). Established to provide collective defense against potential attacks from the Soviet Union, NATO brought together Western nations committed to mutual defense principles. The alliance illustrated the division of Europe during the Cold War, as member countries pledged to defend one another in the face of external threats. NATO has since evolved and expanded to include additional member states, continuing to play a vital role in global security and defense cooperation.