 Guevara 's guerrilla force , numbering about 50 men and operating as the ELN ( Ejército de Liberación Nacional de Bolivia ; " National Liberation Army of Bolivia " ) , was well equipped and scored a number of early successes against Bolivian army regulars in the difficult terrain of the mountainous Camiri region during the early months of 1967 . As a result of Guevara 's units ' winning several skirmishes against Bolivian troops in the spring and summer of 1967 , the Bolivian government began to overestimate the true size of the guerrilla force . But in August 1967 , the Bolivian Army managed to eliminate two guerrilla groups in a violent battle , reportedly killing one of the leaders . 
