Calderio's visit to Prague in the aftermath of the Cuban Missile Crisis served to solidify the ties between Cuba and Czechoslovakia, relations that would persist until the end of the Cold War. Among the activities of Calderio's visit included attendance of 12th Party Congress of the Czechoslovak Communist Party, meeting with Cuban ambassadors to China, Czechoslovakia and Hungary, and a promise to attend the meeting of the Bulgarian Communist Party.

Czech government decision in late September 1959, to approve sending what was euphemistically described as “special technical supplies” or “special technology” (but in truth were weapons, specifically 50,000 submachine guns and ammunition) to Havana, using a neutral Swiss firm as a cut-out to conceal the transaction, especially from American eyes.

This presents evidence of Czechoslovak-Cuban relations forming in 1959, which includes the somewhat sensitive issue of Prague’s attempting to grasp the relationship and balance of power within Havana’s rulers between Fidel Castro’s “July 26th” movement and the traditional, pro-Moscow communist party, the People’s Socialist Party (PSP).