President Juan Emilio Bosch Gaviño, the first democratically elected president of the Dominican Republic, tried to implement a number of social reforms. These action angered the military and Dominican businessmen, who labled Bosch a communist. On September 25, 1963, a group of senior military commanders, expelled President Bosch from the country and installed Donald Reid Cabral as the new president. 

  On April 24, 1965, the Constitutionalistas (Constitutionalists), headed by General Francisco Caamaño, allied with the Dominican Revolutionary Party (DRP) seized the Radio Santo Domingo building and issued calls for rebellion while Constitutionalista officers distributed weapons to their civilian comrades.  Gen Wessin rallied the government troops, the so-called Lealistas (Loyalists), aimed to uphold the military dictatorship and suppress the Constitutionalista rebellion. Later that day, Lealista troops, supported by armored cars and tanks, and the larger Constitutionalista forces battled over the control of  Santo Domingo. One USMC battalion landed in Haina, where it provided assistance to the airlifts of civilians.   On April 29, the U.S. Ambassador, reported that the situation had reached life-threatening proportions for US citizens and that the rebels were communists; called for immediate action. President Johnson authorized the transformation of evacuation operations into a large-scale military invasion through Operation Power Pack, aimed to prevent what the President saw as a second Cuban Revolution. 

  On April 30, 1965, the 3rd Brigade of the 82nd ABN, the 6th Marine Expeditionary Unit, elements of the 7th SFG(A); started the U.S. military intervention in the conflict.  Earlier in the day, the Organization of American States (OAS) also issued a resolution calling the combatants to end all hostilities. At 4:30 p.m., representatives of the Lealistas, the Constitutionalistas, and the U.S. military signed a ceasefire that was to take effect at 11:45 p.m. 

  On May 5, the OAS Peace Committee arrived in Santo Domingo, and a second definite ceasefire agreement was signed, which ended the main phase of the civil war.  Under the Act of Santo Domingo, the 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 prevent some 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. The IAPF  was headed by Brazilian General Hugo Panasco Alvim, with US Army General Bruce Palmer serving as his deputy commander. Utilizing Radio Santo Domingo (RSD) the rebels launched a psychological campaign against the United States, the OAS, and the Loyalists. 

 On May 7, 1965, the Government of National Reconstruction (GNR) was established with Antonio Imbert Barrera as president. On May 14, the GNR initiated Operation LIMPIEZA (Cleanup) an offensive against the rebel-held northern sector. By May 21, GNR troops had completed the destruction of the rebel northern zone and captured Radio Santo Domingo, and following talks with Constitutionalist leaders and Presidential Adviser McGeorge Bundy, a ceasefire was in effect by May 25.

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US Army Special Forces actions during Operation POWER PACK

7th SFG(A) troops arrived 30 April,  on 4 May (D plus 4), additional troops arrived from 7th SFG(A) and 8th SFG(A) and sent into the countryside where they established six sites. The Special Forces had three missions. The overt mission was to deliver food with choppers to various locations. The second mission was gathering intelligence on popular feelings and rebel resistance, and look for signs of Cuban involvement. The third mission was control key points if needed.

  The most important clandestine operation during the intervention was the attempt to silence Radio Santo Domingo (RSD). Virtually every Dominican family owned a radio and, because of the country's high illiteracy rate, relied on it heavily for information. RSD, was the country's national station, capable of being heard throughout the island. In the hands of the rebels, the station became a powerful propaganda weapon-in fact, the "biggest thorn" in the side of the Americans. Langley received a telephone call from a CIA agent with a blunt message. "The difference in Santo Domingo," the agent shouted, "lies in that radio station. If the rebels continue their propaganda they will take over the entire country. The radio must be silenced!"  The problem was that nothing seemed to work. Naval vessels offshore and the Army Security Agency both tried to jam RSD broadcasts, but neither had powerful enough equipment to interfere more than temporarily with the broadcasting range of a commercial station.

  On 8 and 10 May, a reinforced company from the army's 7th SFG(A) led by Col. Edward Mayer, mounted successful air assault operations against RSD transmitter sites at Alto Bandero and La Vega, respectively, thereby reducing the effectiveness of RSD broadcasts in those and surrounding areas. The day after the Special Forces seized the La Vega transmitter, a team of paratroopers and Green Berets slipped into the north and severed telecommunication lines. The operation failed to shut down the radio station, but it did disrupt the telephone system used by the rebels for tactical purposes.  

  After the 25  May cease fire, in addition  to routine activities, the Special Forces performed several special missions. On 19 October they located, seized, and detained Constitutionalists operating an underground pro-rebel newspaper, Patria. On 23 October they reinforced Juan Bosch's personal bodyguard at his residence and after 12 January 1966 maintained surveillance on his activities. And on 17 January they covertly moved the family of Dominican Col. Montes Arache from its home in Puerto Plata, on the northern shore, to Santo Domingo.