 The US ambassador at the time, Lincoln Gordon, and the military attaché, Colonel Vernon A. Walters, kept in constant contact with President Lyndon B. Johnson as the crisis progressed.Johnson urged taking action to support the overthrow of João Goulart by the military, as action against the "left-wing" Goulart government.Operation Brother Sam was the codename given to Kennedy's plan to "prevent Brazil from becoming another China or Cuba".