 On October 3 , 1965 , Castro publicly revealed an undated letter purportedly written to him by Guevara around seven months earlier which was later titled Che Guevara 's " farewell letter " . In the letter , Guevara reaffirmed his enduring solidarity with the Cuban Revolution but declared his intention to leave Cuba to fight for the revolutionary cause abroad . Additionally , he resigned from all his positions in the Cuban government and communist party , and renounced his honorary Cuban citizenship . 
