In 1965 rival factions within the Dominican Republic vied for control of the nation. The so-called Loyalist faction sought to uphold rule by conservative traditionalists; the Constitutionalists, including some left-wing elements, sought to return the Dominican Republic to democratic processes. As conflict between the parties erupted into open warfare the US launched a military intervention.

The Dominican Republic had a long and troubled history and a difficult relationship with democracy. Following an occupation by the US military in the early twentieth century, Rafael Trujillo controlled the country as president, or through his sons and proxies, until his assassination in 1961. On 27 February 1963, Juan Emilio Bosch Gaviño, the first democratically elected president of the Dominican Republic, was sworn into office, only to be toppled by a military coup in September of the same year and replaced by Donald Reid Cabral. Reid failed to attract popular support and several factions became involved in a power struggle. The so-called Lealistas (Loyalists), headed by Generals Pedro Benoit and Antonio Imbert, aimed to uphold a military dictatorship. The Constitutionalistas (Constitutionalists),headed by General Francisco Caamaño, and allied with the Dominican Revolutionary Party, supported Bosch.

In April 1965, three junior officers demanded a meeting with President Reid. When he refused, and sent Chief of Staff Riviera Cuesta instead, the latter was arrested. A group of constitutionalists from within the military then seized Radio Santo Domingo and issued calls for sedition, prompting several units to defect and abandon their position, while other officers began distributing arms to their civilian sympathisers. Appointing General Wessin y Wessin as the new Chief of Staff, Reid attempted to rally the remaining armed forces around himself and suppress the rebellion. Conflict spread, drawing in elements of the Dominican Republic’s army, navy and air force, and the country teetered on the edge of a full-blown civil war.

At that point in time, the United States of America became involved. Initially planned as an evacuation of about 3,500 US citizens, early on 27 April over 1,100 expatriates were airlifted out of the country by the US military. However, as Lealista troops marched on the capital, rebels secured their positions and executed a number of police officers, and a US Marine was killed by a rebel sniper, the US Ambassador declared the insurgents to be communists and demanded that US President Lyndon B Johnson act immediately. Johnson ordered a transformation of evacuation into an all-out military intervention: Operation Power Pack.