Under the Lyndon B. Johnson Administration, which gained power after the assassination of John F. Kennedy, the US took a more hardline stance on Latin America—sometimes called the "Mann Doctrine". In 1964, the Brazilian military overthrew the government of president João Goulart with US backing. In late April 1965, the US sent some 22,000 troops to the Dominican Republic for a one-year occupation in an invasion codenamed Operation Power Pack, citing the threat of the emergence of a Cuban-style revolution in Latin America. Héctor García-Godoy acted as provisional president, until conservative former president Joaquín Balaguer won the 1966 presidential election against non-campaigning former President Juan Bosch. Activists for Bosch's Dominican Revolutionary Party were violently harassed by the Dominican police and armed forces.