 Only a small band of revolutionaries survived to re @-@ group as a bedraggled fighting force deep in the Sierra Maestra mountains , where they received support from the urban guerrilla network of Frank País , the 26th of July Movement , and local campesinos . With the group withdrawn to the Sierra , the world wondered whether Castro was alive or dead until early 1957 when the interview by Herbert Matthews appeared in The New York Times . The article presented a lasting , almost mythical image for Castro and the guerrillas . Guevara was not present for the interview , but in the coming months he began to realize the importance of the media in their struggle . Meanwhile , as supplies and morale diminished , and with an allergy to mosquito bites which resulted in agonizing walnut @-@ sized cysts on his body , Guevara considered these " the most painful days of the war " . 
