<P> The nuclear arms race brought the two superpowers to the brink of nuclear war . In 1962, President John F. Kennedy responded to the installation of nuclear missiles in Cuba with a naval blockade--a show of force that brought the world close to nuclear war . The Cuban Missile Crisis showed that neither superpower was ready to use nuclear weapons for fear of the other's retaliation, and thus of mutually assured destruction . The aftermath of the Cuban Missile Crisis led to the first efforts toward nuclear disarmament and improving relations . (Palmowski) </P> <P> By 1964, under President Johnson, the program to discriminate against dictatorial regimes ceased . In March 1964, the US supported a military coup in Brazil, overthrowing left - wing president, João Goulart, and was prepared to help if called upon under Operation Brother Sam . In 1965, the US dispatched 24,000 soldiers to the Dominican Republic to prevent a possible left - wing take over under Operation Power Pack . Earlier the OAS issued a resolution calling the combatants to end all hostilities . On May 5, the OAS Peace Committee arrived in Santo Domingo and a second definite cease fire agreement was signed, ending the main phase of the civil war . Under the Act of Santo Domingo, OAS was tasked with overseeing the implementation of the peace deal as well as distributing food and medication through the capital . The treaties failed to fully prevent violations such as small scale firefights and sniper fire . A day later, OAS members established the Inter-American Peace Force (IAPF) with the goal of serving as a peacekeeping formation in the Dominican Republic . IAPF consisted of 1,748 Brazilian, Paraguayan, Nicaraguan, Costa Rican, Salvadoran and Honduran troops and was headed by Brazilian general Hugo Panasco Alvim, with Bruce Palmer serving as his deputy commander . </P> <P> On May 26, U.S. forces began gradually withdrawing from the island . The first post war elections were held on July 1, 1966, pitting Reformist Party candidate, Joaquín Balaguer, against former president Juan Emilio Bosch Gaviño . Balaguer emerged victorious in the elections, after building his campaign on promises of reconciliation . On September 21, 1966, the last OAS peacekeepers withdrew from the island, ending the foreign intervention in the conflict . </P> <P> Through the Office of Public Safety, an organization dependent of the USAID and close to the CIA, the US assisted Latin American security forces, training them in interrogation methods, riot control, and sending them equipment . Dan Mitrione, in Uruguay, and Luis Posada Carriles, in Venezuela, became infamous for his systematic use of torture . </P>

In which of these latin american nations did the united states intervene in april of 1964