 As an additional obstacle , white South African mercenaries , led by Mike Hoare in league with Cuban exiles and the CIA , worked with the Congo National Army to thwart Guevara 's movements from his base camp in the mountains near the village of <unk> on Lake Tanganyika in southeast Congo . They were able to monitor his communications and so pre @-@ empted his attacks and interdicted his supply lines . Although Guevara tried to conceal his presence in Congo , the United States government knew his location and activities . The National Security Agency was intercepting all of his incoming and outgoing transmissions via equipment aboard the USNS Private Jose F. Valdez ( T @-@ AG @-@ 169 ) , a floating listening post that continuously cruised the Indian Ocean off Dar es Salaam for that purpose . 
