During the 1962 missile crisis in the USA with Russia. In his own words: “During the serious international ordeal of October 1962, when the Kennedy/Kruschev crisis blew up due to Russian nuclear missiles shipped to Fidel Castro’s Cuba, he released important information to the Caracas American embassy on caves that had been visited in the country by the polish engineer that was accused in world press as one of the technicians that set up rockets with nuclear warheads in Cuban caves: Maciej Kuczynski” ("Letter to the USA Embassy in Caracas Venezuela, August 5, 1995"). It happens to be that both himself and Kuczynski were speleologists and had initiated a fair correspondence since June 1958. Thus it happened that Kuczynski mentioned in some detail in his 1962 letters to de Bellard quite a number of Cuban caves he had explored. Such information was presented as a help to be used by American intelligence for exactly locating where the missiles threatening the USA were placed.