[Note the US Occupation of the Dominican Republic 1916-1924.]

The assassination of Cáceres turned out to be but the first act of a frenzied drama that culminated in the republic's occupation by the United States. The fiscal stability that had resulted from the 1905 receivership eroded under Cáceres's successor, Eladio Victoria y Victoria; most of the increased outlays went to support military campaigns against rebellious partisans, mainly in the Cibao. The continued violence and instability prompted the administration of President William H. Taft to dispatch a commission to Santo Domingo on September 24, 1912, to mediate among the warring factions. The presence of a 750-member force of United States Marines apparently convinced the Dominicans of the seriousness of Washington's threats to intervene directly in the conflict; Victoria agreed to step down in favor of a neutral figure, Roman Catholic archbishop Adolfo Alejandro Nouel Bobadilla. The archbishop assumed office as provisional president on November 30.

Nouel proved unequal to the burden of national leadership. Unable to mediate successfully between the ambitions of rival horacistas and jimenistas, he stepped down on March 31, 1913. His successor, José Bordas Valdés, was equally unable to restrain the renewed outbreak of hostilities. Once again, Washington took a direct hand and mediated a resolution. The rebellious horacistas agreed to a cease-fire based on a pledge of United States oversight of elections for members of local ayuntamientos and a constituent assembly that would draft the procedures for presidential balloting. The process, however, was flagrantly manipulated and resulted in Bordas's reelection on June 15, 1914. Both horacistas and jimenistas took offense at this blatant maneuver and rose up against Bordas.

The United States government, this time under President Woodrow Wilson, again intervened. Where Taft had cajoled the combatants with a clear intimation of military action, Wilson delivered an ultimatum: elect a president or the United States will impose one. The Dominicans accordingly selected Ramón Báez Machado as provisional president on August 27, 1914. Comparatively fair presidential elections held on October 25 returned Jiménez to the presidency. Despite his victory, however, Jiménez felt impelled to appoint leaders and prominent members of the various political factions to positions in his government in an effort to broaden its support. The internecine conflicts that resulted had quite the opposite effect, weakening the government and the president and emboldening Secretary of War Desiderio Arias to take control of both the armed forces and the Congress, which he compelled to impeach Jiménez for violation of the constitution and the laws. Although the United States ambassador offered military support to his government, Jiménez opted to step down on May 7, 1916.

Arias never formally assumed the presidency. The United States government had apparently tired of its recurring role as mediator and had decided to take more direct action. United States forces had already occupied Haiti by this time. The initial military administrator of Haiti, Rear Admiral William Caperton, had actually forced Arias to retreat from Santo Domingo by threatening the city with naval bombardment on May 13. The first Marines landed three days later. Although they established effective control of the country within two months, the United States forces did not proclaim a military government until November. Most Dominican laws and institutions remained intact under military rule, although the shortage of Dominicans willing to serve in the cabinet forced the military governor, Rear Admiral Harry S. Knapp, to fill a number of portfolios with United States naval officers. The press and radio were censored for most of the occupation, and public speech was limited.

The surface effects of the occupation were largely positive. The Marines restored order throughout most of the republic (with the exception of the eastern region); the country's budget was balanced, its debt was diminished, and economic growth resumed; infrastructure projects produced new roads that linked all the country's regions for the first time in its history; a professional military organization, the Dominican Constabulary Guard, replaced the partisan forces that had waged a seemingly endless struggle for power. Most Dominicans, however, greatly resented the loss of their sovereignty to foreigners, few of whom spoke Spanish or displayed much real concern for the welfare of the republic.

The most intense opposition to the occupation arose in the eastern provinces of El Seibo and San Pedro de Macorís. From 1917 to 1921, the United States forces battled a guerrilla movement in that area known as the gavilleros. The guerrillas enjoyed considerable support among the population, and they benefited from a superior knowledge of the terrain. The movement survived the capture and the execution of its leader, Vicente Evangelista, and some initially fierce encounters with the Marines. However, the gavilleros eventually yielded to the occupying forces' superior firepower, air power (a squadron of six Curtis Jennies), and determined (often brutal) counterinsurgent methods.

After World War I, public opinion in the United States began to run against the occupation. Warren G. Harding, who succeeded Wilson in March 1921, had campaigned against the occupations of both Haiti and the Dominican Republic. In June 1921, United States representatives presented a withdrawal proposal, known as the Harding Plan, which called for Dominican ratification of all acts of the military government, approval of a loan of US$2.5 million for public works and other expenses, the acceptance of United States officers for the constabulary--now known as the National Guard (Guardia Nacional)--and the holding of elections under United States supervision. Popular reaction to the plan was overwhelmingly negative. Moderate Dominican leaders, however, used the plan as the basis for further negotiations that resulted in an agreement allowing for the selection of a provisional president to rule until elections could be organized. Under the supervision of High Commissioner Sumner Welles, Juan Bautista Vicini Burgos assumed the provisional presidency on October 21, 1922. In the presidential election of March 15, 1924, Horacio Vásquez Lajara handily defeated Francisco J. Peynado. Vásquez's Alliance Party (Partido Alianza) also won a comfortable majority in both houses of Congress. With his inauguration on July 13, control of the republic returned to Dominican hands.