After promising protection to several Dominican frontier governors and securing their allegiance, Boyer invaded the Dominican Republic with a force of 50,000 soldiers in February 1822. These forces encountered resistance from the white population. On February 9, 1822, Boyer formally entered the capital city, Santo Domingo, where Núñez turned over the keys to the city. Dominicans reacted uneasily to the Haitian invasion.
The island of Hispaniola was now united under one government from Cape Tiburon to Cape Samana. By awarding land to Haitian military officers at the expense of former members of the Spanish forces of Santo Domingo, Boyer reduced his influence with the Spanish-Haitian leadership. He continued the policy of Alexandre Petion, his former political mentor, of helping free people of color in other Spanish Latin American colonies resist the Spanish crown. Boyer ignored Haitian political opponents who called for reforms, such as parliamentary democracy, and veteran generals of the War of Independence, who believed that the revolution was not complete and that they were being neglected.