The PSP at first played little part in
Fidel Castro's armed struggle against the dictatorship of General
Fulgencio Batista, which took place mainly in the countryside, and only threw its weight behind Castro's guerrilla campaign a few months before Batista finally fled the country. Until then, it had tended to denounce the young rebels' "adventurism." Despite this background of mistrust, when Castro moved the revolution sharply to the left in the early 1960s, he found a use for the PSP apparatus, and for young but experienced activists such as Malmierca, in giving a disciplined organizational underpinning to his embryonic regime. Malmierca was one of the founders of the powerful state security apparatus — a role for which his reluctance to reveal even the most innocuous details about his personal life must have been an advantage. He was one of the functionaries who supervised the merger of the PSP with Castro's
July 26 Movement to form the Cuban Communist Party in 1965. In both of these functions, Malmierca had to balance the professional politicians and the young idealists who had followed Castro into the hills in the mid-1950s. He performed this difficult task well enough to earn advancement, becoming a member of the new party's central committee and being made editor of its official organ, the daily newspaper
Granma. == Foreign minister ==