Che Guevara
In Guevara's private writings from this time (since released), he displays his growing criticism of the Soviet political economy, believing that the Soviets had "forgotten Marx". This led Guevara to denounce a range of Soviet practices including what he saw as their attempt to "air-brush the inherent violence of class struggle integral to the transition from capitalism to socialism", their "dangerous" policy of peaceful co-existence with the United States, their failure to push for a "change in consciousness" towards the idea of work, and their attempt to "liberalize" the socialist economy. Guevara wanted the complete elimination of money, interest, commodity production, the market economy, and "mercantile relationships": all conditions that the Soviets argued would only disappear when world communism was achieved. Disagreeing with this incrementalist approach, Guevara criticized the "Soviet Manual of Political Economy", correctly predicting that if USSR did not abolish the law of value (as Guevara desired), it would eventually return to capitalism.
Che Guevara
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.