During the long Dominican War of Independence (1844–1856), mostly fought as an insurgency, the country was depopulated, impoverished, indebted, politically fragmented, corrupt, iliterate, and open to Haitian incursions.

[1][2] Starting in 1846, the two most prominent Dominican leaders, Pedro Santana and Buenaventura Báez, repeatedly offered the United Kingdom and France a protectorate or annexation as a way to repair the economy and keep their own factions in power.

[1] Britain and France opposed annexation by Spain, and discussed protectorates by Sardinia, Sweden, Denmark, Portugal, Naples, the Netherlands, Belgium, and even Haiti as alternatives in 1859.

Though they met little interest at first, prime minister Leopoldo O'Donnell sent a military mission to train the Dominican Army and explore the strategic value of the country for Spain.

[1] Communication was established between Santana and the Spanish captain-general of Cuba Francisco Serrano, who was instructed to negotiate but not to move precipitously in order to avoid conflict with the United States.

"[6] Frustrated with Spain's slowness, Santana staged a plebiscite in March 1861 in which 4,000 Dominicans voted overwhelmingly for annexation (the total population of the country was 280,000).

[1] It was also agreed that Dominican paper money, devalued due to hyperinflation caused by mass printing to finance the war against Valverde and a military buildup against possible Haitian invasions, would be exchanged by Spanish currency as if they had the same value.

In addition, up to 20 warships cordoned the Dominican coast at the height of Spanish deployment, in order to prevent foreign interference (chiefly from Haiti or the United States).

The main supporters of the annexation were the "propertied classes, aristocrats, Catalan industrialists, urban landowners, military, and religious leaders," who believed it would revitalize Spain's image and economy, restore Catholicism in the island, and protect Cuba.

[1] After the annexation's announcement, the Dominican generals José María Cabral and Francisco del Rosario Sánchez rebelled against Santana and occupied some villages along the border with Haiti, which allowed them to operate in its territory and provided them with weapons.

He requested the urgent shipment of public officials to organize the administration, and that Santana be called to Spain with the excuse of meeting queen Isabella II, be given a title in Castile and a seat as a senator to keep him there, while another governor and captain-general was appointed in his place.

[2] Spain sent engineers to study the construction of roads, railroads, mines, river channels, docks and bridges; and jurists and public officials to organize the Dominican administration.

[1] However in March, the Spanish official Alonso Colmenares, assigned to organize justice, denounced that Santana still opposed any modernization and behaved like a dictator, breaking the law and usurping the queen's authority to give pardons.

In September, Rivero made a new report confirming Serrano's conclusions and added that the country was divided between supporters of Báez and Santana, threatening peace.

In August, Dominican dissidents in collaboration with the Haitian rebel Sylvain Salnave established sanctuaries along the Haitian-Dominican border to their mutual advantage.

On August 16, fourteen dissidents led by Santiago Rodríquez, Benito Morción, and José Cabrera crossed the northeast frontier into Santo Domingo and called for the nation to rise up against the invaders.

On September 9, Spanish reinforcements of two battalions arrived at Puerto Plata on board the Isabel la Católica and the El Pájaro del Océano.

On September 14, the insurgents established a provisional government led by General José Antonio Salcedo in Santiago de los Caballeros.

The Captain-General of Santo Domingo, now the Spaniard José de la Gándara y Navarro, embraced a strategy of occupying the northern ports, thus cutting off the dissident Dominican government in Santiago from outside support.

The Spanish attacked and captured Monte Cristi, but sustained heavy losses, including the wounding of Field Marshal Primo de Rivera.

Realizing that the reconquest of Santo Domingo would be costly and complicated due to the ending of the U.S. Civil War, the Queen authorized the abandonment of the territory on May 3, 1865.

The departure of Spain resulted in a reduction of her influence in the Caribbean Sea and an approach between the Dominican Republic and the United States, motivated by Báez's intention to solidify his power and Andrew Johnson's renewed interest in a naval base in Samaná.

Spain's reasons for recognition included the limitation of US influence, preventing the US lease of Samaná, and reducing the use of the Dominican Republic as a sanctuary for Cuban and Puerto Rican separatists.