In 1954 Oliva was commissioned as a second lieutenant in the Cuban Army after graduating from the Cuban Military Academy, "the Cadet School." After graduating with honors from the Artillery Academy in 1955 he was appointed professor of Artillery in the Cadet School until 1958. From 1958 to 1959 he was a student, also graduating with honors, and an instructor at the US Army Caribbean School in the Canal Zone, Panama. In late 1959 after the Castro revolution overthrew General Batista, the Cuban army was "purged", but Oliva was appointed General Inspector at the INRA. In May 1960 he was one of a group of former Cuban officers planning a campaign against the Castro regime. They were all graduates of Cuba's military academy. He left the army early in August 1960 and flew to Miami. On August 29, 1960, Oliva and about 40 young Cuban exiles, recruited by the Central Intelligence Agency were transported via CIA C-54 aircraft to San José, Guatemala to perform guerrilla training that later became conventional.