 "Missouri" arrived at Rio de Janeiro on 30 August 1947 for the Inter-American Conference for the Maintenance of Hemisphere Peace and Security.President Truman boarded on 2 September to celebrate the signing of the Rio Treaty, which broadened the Monroe Doctrine by stipulating that an attack on any one of the signatory American countries would be considered an attack on all.The Truman family boarded "Missouri" on 7 September 1947 to return to the United States and disembarked at Norfolk on 19 September.