At an early age, he joined the Cuban Revolutionary Army and fought in the "Guerra de Diez Años" (Ten Years' War) attaining the rank of colonel.

[2] He was captured and imprisoned in El Morro Castle where he escaped,[2] and returned to organize a rebel group to operate in San Diego del Valle until 1880 when José Martí convinced him that Cuban independence was not feasible at the moment.

From the United States he sent arms, ammunition and food to Cuba as Commander in Chief of the Department of Expeditions until 1885.

[1] He was the Civil Governor of the Province of Havana from 1899 to 1902 and was the first person to raise the flag of Cuba at El Morro Castle on May 20, 1902, at noon.

[1] Núñez served as Cuban Secretary of Agriculture, Commerce and Labor in 1913 and as Vice President of Cuba from 1917 to 1921.