Conventional wisdom has the Korean War putting the O in NATO. Prior to that time, from the signing of the North Atlantic Treaty on April 4, 1949, to the North Korean invasion of South Korea on June 25, 1950, the Treaty allies were just going through the motions of establishing an organisation. Historian Lawrence Kaplan argues that this is a mistaken view, and he fills significant blanks in the record of 1949 and 1950, which NATO officials and analysts alike have largely ignored.