The paramount purposes of the pact are peace and security... It is clear that the North Atlantic Pact is not an improvisation. It is the statement of the facts and lessons from two world wars in less than half a century. That experience has taught us that the control of Europe by a single aggressive, unfriendly Power would constitute an intolerable threat to the national security of the United States... We must make it clear that armed attack will be met by collective defence, prompt and effective. That is the meaning of the North Atlantic Pact.
Dean Acheson, radio broadcast (18 March 1949), quoted in The Times (19 March 1949), p. 4