NATO's Military Buildup Originated from the Korean War Proxy Conflict
The Warsaw Pact was formed in 1955 as a response to West Germany joining NATO.
France's 1966 Withdrawal from NATO: De Gaulle's Pursuit of Military Independence and Rejoining in 2009
NATO's first Article 5 invocation after 9/11 marked a significant role shift, while expanding membership to include Spain, Czech Republic, Hungary, and Poland.
Former Warsaw Pact states join NATO post-Cold War, expanding its membership significantly.