Relations have long been hostile due to substantial ethnic and cultural differences, historic conflicts, territorial disputes, and sharing the island of Hispaniola, part of the Greater Antilles archipelago in the Caribbean region.

Spain developed a settler-based society with a white and mixed-race majority, while the French brought masses of African slaves to their side of the island.

The native Tainos suffered a steep population decline early on due to brutal enslavement, warfare, and intermixing with the Spanish colonizers.

At Dessaline's order, a genocide against people of European descent was perpetrated, which resulted in the ethnic cleansing of the remaining French population of Haiti.

With the outbreak of the Haitian Revolution, the rich urban families linked to the colonial bureaucracy left the island, while most of the rural hateros (cattle ranchers) remained, even though they lost their principal market.

This period called the Era de Francia, lasted until 1809 until being recaptured by the Dominican general Juan Sanchez Ramirez in the reconquest of Santo Domingo.

[citation needed] This genocidal invasion claimed the lives of nearly half of the inhabitants of the Spanish side of the island, including children, men, women, and elders of black, mixed, and white racial backgrounds.

Some wealthy cattle ranchers had become rulers, and sought to bring control and order in the southeast of the colony where the "law of machete" ruled the land.

in the frontier region had expressed interest in uniting the entire island, while they sought power with military support from Haitian officials against their enemies.

[citation needed] In 1838, Juan Pablo Duarte, an educated nationalist, founded a resistance movement called La Trinitaria ("The Trinity") along with Ramón Matías Mella and Francisco del Rosario Sánchez.

In 1843, Haitian conspirators made a breakthrough as they overthrew President Jean-Pierre Boyer, while placing another mulatto Charles Rivière-Hérard in charge.

[20] Dominican nationalists decided to take action with the leadership of Francisco del Rosario Sánchez, Ramón Matías Mella, and Pedro Santana, a wealthy cattle-rancher from El Seibo who commanded a private army who worked on his estates.

On February 27, 1844, some 100 Dominicans seized the fortress of Puerta del Conde in the city of Santo Domingo, and the following day the Haitian garrison surrendered.

After this victory, the Dominicans withdrew their headquarters to the Ocoa River, and the valleys of Baní, where their cavalry and lancers could operate; and in this way, they restrained the march of the Haitians, who could not advance beyond Azua; and having then attempted to open a way through the passes of the Maniel, they were in every re-encounter driven back with loss.

[20] In a significant naval action between the Hispaniolan rivals, a Dominican squadron captured 3 small Haitian warships and 149 seamen off Puerto Plata on December 21.

Dominican General (and presidential contender) Santana raised 800 soldiers and, with the help of several gunboats, routed the Haitian invaders at the Battle of Las Carreras on April 21–22.

[20] In an attempt to forestall yet another Haitian invasion, in November 1849, Dominican President Buenaventura Báez launched a naval offensive against Haiti.

On December 3, the squadron composed of the brigantines 27 de Febrero and General Santana and the schooners Constitución and Las Mercedes and commanded by Juan Alejandro Acosta, bombarded and burned the town of Petit Rivière.

[29] In November 1855, Soulouque, having proclaimed himself Emperor Faustin I of a Haitian empire which he hoped to expand to include the Dominican Republic, invaded his neighbor again.

[35] Upon Soulouque's arrival in Port-au-Prince with the remaining remnants of his army, he faced vehement curses from women who had lost their sons, brothers, and husbands in the war.

Despite this, the Dominican dictator Rafael Trujillo subsequently launched a wave of anti-Haitian violence in 1937, culminating in the Parsley massacre in which tens of thousands of Haitians were forced across the border or killed.

The economic downturn in Haiti has been the result of factors such as internal power struggles, rapid population growth, environmental degradation, and trade embargoes.

The two governments have been unable to agree upon a legal framework to address the nationality of these descendants, leaving around one million people of Haitian ancestry in the Dominican Republic effectively stateless, restricting their access to health care, education and employment opportunities.

Over the past years tensions have risen, causing the International Organization for Migration to offer Haitians $50 each plus additional relocation assistance to return to Haiti.

[58][59] The project includes 70 watchtowers and 41 access gates for patrolling containing fiber optics for communications, movement sensors, cameras, radars and drones.

The project is controversial, with claims that it will do little to reduce illegal migration, will encourage bribery of Dominican Republic soldiers, and will become a source of conflict.

The closure (and militarization) of the Dominican Republic-Haiti border occurred in response to the construction of the Pittobert irrigation canal on the binational river known as Dajabón.

This stance is based on the non-consultative nature of the canal and the fact its plans involve a diversion of the binational river, which forms the entire northernmost part of the border between the Dominican Republic and Haiti.

Jesuit priests and leftist organizations who work on the Dominican border have both spoken out in favor of fair use of the Dajabón River water by both countries.

They also denounced mining exploitation plans that consume and contaminate enormous amounts of water, set to take place in the same Dominican border province of Dajabón (as the Pittobert irrigation canal).