Narciso inherited the occupation from his father, Fernando Raimundo Sánchez, (who was part of the free black population) of which mostly took place in the east, an area where livestock production was concentrated.

He was also influenced by his father and aunt, Maria Trinidad Sánchez, both involved in the movement Revolution of Los Alcarrizos, an early resistance that attempted to challenge the dictatorship of Jean-Pierre Boyer, who was the main architect of the regime.

In 1838, Duarte founded the movement La Trinitaria, a nationalistic organization that intends to bring freedom to the Dominican people, who during this time were living in tyranny under Haitian rule.

Sánchez's significance is seen in that he was one of those who led the overthrow of the Haitian authorities of Santo Domingo appointed by Jean Pierre Boyer, deposed at the end of March 1843 by the movement called La Reforma.

In 1843, when Duarte went into exile in Curaçao for fear of being assassinated or imprisoned by the Haitian authorities, Sánchez, then 25 years old, assumed the leadership of the independence movement La Trinitaria, where he presided over the group's meetings and expanded contacts with representatives of the most important social sector in the city, with the collaboration of fellow member Matías Ramón Mella.

The letter portrays the situation that the efforts in pursuit of independence were going through:[18] Juan Pablo: With Mr. José Ramón Chaves Hernández we write to you on November 18, imposing on you the political state of this city and the needs we have for you to (get) help for the triumph of our cause.

From information that Pedro Alejandro Pina received and transmitted to Duarte, in a letter dated November 27, 1843, it is deduced that the Trinitarios had recovered from Hérard's repression and were gaining strength, while the French supporters were weakening.

The reigning party awaits you as general in chief, to begin that great and glorious revolutionary movement, which will bring happiness to the Dominican peopleA few days after the first letter it must have become clear to Sánchez that the sector he led found it impossible to produce independence on its own and that, therefore, it was imperative to reach an agreement with people of other orientations.

The document is titled “Demonstration of the peoples of the Eastern Part of the formerly Spanish Island or of Santo Domingo, on the causes of its separation from the Haitian Republic” and is known as the Manifesto of January 16 due to the date on which it was read for the first time.

[22] In one of the paragraphs of the manifesto, Sánchez denotes his firm decision to achieve the objective contained in the Trinitarian oath:[1] We believe we have demonstrated with heroic constancy, that the evils of a government must be suffered while they are bearable, rather than do justice by abolishing forms; but when a long series of injustices, violations, and insults, continuing to the same end, denote the design of reducing everything to despotism and the most obsolete tyranny, it is the sacred right of the peoples and their duty to throw off the yoke of such a government and provide for new guarantees ensuring its future stability and prosperity and adds: "Twenty-two years ago, the Dominican People, through one of those fatalities of fate, are suffering the most ignominious oppression...The manifesto, having already been unified by the alliance made between liberals and conservatives, changed the word independence for reparation, culminating these words:[1] To the Dominican union!

Since the opportune moment is presented to us from Neiba to Samaná, from Azua to Montecristi, the opinions are in agreement and there is no Dominican who does not exclaim with enthusiasm: Separation, God, Homeland and Freedom.Meeting at the house of Sánchez, on February 24, 1844, the Trinitarios discussed on the plans on the uprising.

In addition to Sánchez and Mella, Vicente Celestino Duarte, José Joaquín Puello, those of La Concha (Jacinto and Tomás), Juan Alejandro Acosta and many others attended that meeting.

On February 29, apparently of his own free will, Sánchez handed over the presidency of the Board to Bobadilla, in recognition of the role that the conservative sector was called to play from now on, with more social influence than the Trinitarios among the rural population of the interior from the country.

However, Pedro Santana, at the head of the Army of the South, advanced to Santo Domingo and on July 12, 1844 gave a counterattack, expelling the Trinitarios from the Central Government Board, and the Seibano leader was sworn in as President of the Republic.

The young Trinitarios, previously revered as the architects of the Dominican nationalism, had to suffer the most unlikely persecutions, exiles, imprisonments and executions, as well as receive false moral insults with the intention of piercing their lineage.

As a sad paradox of fate, six months after the consummation of National Independence, on August 22, 1844, the Central Government Board led by Pedro Santana, issued a resolution declaring the Trinitario chiefs (Duarte, Sánchez and Mella) "traitors to the Homeland” and deported them in perpetuity.

Not having verified the meeting of this body due to the flight from Azua, I continued my march until I reached Baní where I received a written order, from the general in chief of the army Pedro Santana, which I still have, to deliver the troops under my command to Lieutenant Colonel Dionicio Cabral, who was to lead them to Portesuelo where there was the greatest need for them.

It was then that General Santana, apart from the salutary measures he had already taken to improve the order of the campaign, began his ingenious and happy operations on the Las Carreras field, incorporating into the army of action even his own guard for the night.

I reiterated this claim, there where lies are not spoken; there where the colors of the enemy flags could be distinguished, but General Santana answered me that he wanted me to be in his company and he repeated these same words in his memorable proclamation to the army in Las Carreras field.

[27] Moved by this cautious attitude, and although retired from the practice of the profession, in 1853, Sánchez published the article Amnesty, in which he congratulated Santana for his willingness to allow the return of all those politically persecuted as a result of taking the presidency by third time, and elevated him to the status of the nation's greatest hero.

One of the most significant events of his career took place on August 12, 1859, in a high profile case involving a charge of adultery against Víctor George, an artillery captain with the rank of lieutenant colonel.

Sánchez assumed George's defense, displaying his skills as a lawyer, and finished his closing argument with the following words:[30] Magistrates, today you are going to rule on a cause célèbre, as should also be your decision.

(Upon learning of the Sánchez expedition in the south, Victor George left on foot to take part in the struggle in a gesture of gratitude, but was killed near the city of Azua by Pedro Santana's supporters).

But Lamothe's position was a minority, so Sánchez was forced to present, on March 20, a memorandum to the two ministers with whom he was negotiating, in which he explained his conceptions of what cordial relations between the two countries should be: two sovereign nations that divided the island, with full recognition of one another's existence.

That is why I have come to ask you to pass the borders and resources with which to prevent the annexation that is planned to be carried out.Although initially skeptical, he eventually agreed to give aid to the rebels due to the possibility of Spain stretching its power to the rest of the island.

[35] In it, he addressed a proclamation to his enemies, publicly denouncing Santana's actions, his firm stance to confront the invading Spanish army, and calling on the Dominicans to take up arms against the upcoming threat that was approaching.

I have believed that I am fulfilling a sacred duty, putting myself in charge of the reaction that prevents the execution of such criminal projects and you must conceive, of course, that, in this revolutionary movement, there is no risk to national independence or your liberties, when organized by the instrument that Providence used to raise the first Dominican flag.

[37] Meanwhile, Cabral received information that the Haitian government had decided to withdraw support for the Dominican revolutionaries, forced by threats from a Spanish squadron that was stationed in the bay of Port-au-Prince.

The second corporal Antonio Peláez de Campomanes, the most senior Spaniard in the government, opposed the trial because he perceived that the death sentence of the captured expedition members was going to constitute a disastrous precedent that would undermine the prestige of Spain.

Sánchez, two-time hero and Founding Father of the Dominican Republic, was shot dead on July 4, 1861, in San Juan de la Maguana, at the young age of 44.