 During Guevara 's time living hidden among the poor subsistence farmers of the Sierra Maestra mountains , he discovered that there were no schools , no electricity , minimal access to healthcare , and more than 40 percent of the adults were illiterate . As the war continued , Guevara became an integral part of the rebel army and " convinced Castro with competence , diplomacy and patience " . Guevara set up factories to make grenades , built ovens to bake bread , taught new recruits about tactics , and organized schools to teach illiterate campesinos to read and write . Moreover , Guevara established health clinics , workshops to teach military tactics , and a newspaper to disseminate information . The man who three years later would be dubbed by Time Magazine : " Castro 's brain " , at this point was promoted by Fidel Castro to Comandante ( commander ) of a second army column . 
